Full HZJ80 brake system rebuild - booster to rotor (1 Viewer)

[DivByZero]

In this thread, I'm going to give a comprehensive summary of the full brake system rebuild I just did on my HZJ80. I'm going to walk through replacing the master cylinder, all the soft lines, front rotors, splitting and fully rebuilding the calipers, and replacing and calibrating the LSPV. Some of this info is on MUD here and there, but I was surprised how much was missing. I'm aiming to make this thread a complete reference for anyone who wants to work on any part of the brake system.

A few notes first. My 80 series is a RHD HZJ80, 1996 model. It has disc brakes front and rear. It doesn't have ABS, this spec vehicle didn't come with it. There will be some differences with LHD and ABS vehicles.

This is definitely at least a job. It requires more than one day, attention to detail, and specialised tools you won't have on hand unless you've done a job like this before.

Right, let's get into it. Here's my 80:

Great vehicle. Had it for about 7 years now, been on a lot of adventures. I've had cause to marvel at how in the time I've owned it, I hadn't had to change the front brake pads. I got suspicious when the rears ran low recently, which I'd changed once before, that the front calipers were actually stuck. I also had a very slow leak on one of the hoses, and an aftermarket master cylinder from a PO that I wanted to replace. I opted to do everything at once, and go scorched earth, replacing everything with genuine parts and getting the brake system back to factory new condition end to end.

Almost. There are two things I didn't do in this process. First of all, my brake booster. It has no leaks, works well. I left it undisturbed. That's simple to do, because it's "above" the hydraulic part of the system. You can easily do the brake booster separately from the master cylinder down, and that's what I'd advise you to do. Secondly, I didn't replace my rear rotors. I replaced the rear rotors about 4 years ago, when I went scorched earth on the parking brake system, of which the rotors form an integral part. Everything else, I'll cover below.

First of all, you'll need a ton of parts:

Go genuine. Don't go aftermarket. Get genuine pads, rotors, lines, the whole set. I'll probably provide a list of part numbers in a following post. For now, feel free to ask questions here.

Time to jack up the vehicle and pull the wheels. Two sets of jack stands will make your life easier, but you could do it with one, it'll just mean more screwing around. I'll start at the rear:

Two bolts, 17mm from memory, holding in each caliper. Go ahead and pull them. You'll make your life a little easier if you break the slide pins loose too while it's still mounted on the car, but leave them threaded for now. Now it's time to disconnect the brake line from the caliper:

Leave the brake line dangling, drizzling a nice stream of amber fluid. A container below isn't a bad idea:

Repeat on the other rear caliper. Now let's pull the fronts:

Repeat for the other side. You should now have all the calipers off. I'm going to continue removing parts, now onto the Load Sensing Proportional Valve (LSPV). You've got easy access with the rear left wheel removed:

 

[DivByZero]

If you're careful, you can remove the LSPV without loosening or changing the adjusting arm. If your rig is like mine, you'll be able to see the calibrated height for the LSPV based on the crud around the bracket. To get the LSPV off however, and the other flared brake line fittings, you'll need a flared brake line tool. Do NOT cheap out on this. If you strip the nuts on your brake lines, which are probably frozen solidly in place, you're in for a world of pain. What you should get is this:

This is the genuine Toyota SST, 09751-36011. It has a 10mm and 12mm (which you won't use) flared brake nut spanner ends. This is easily available from your Toyota dealer or online, for a really good price. Unfortunately, when I started, I forgot I hadn't picked this up from my dealer, it was waiting at the counter, but it was a Saturday and they were closed on the weekend, so I forked out twice as much and got a high quality set, Repco branded like most of my tools:

This was NOT as good as the genuine Toyota one. It felt like it had more flex on the open end. It still did the job, but I'd recommend the Toyota one over any other option. You only need a 10mm size.

After this, let's pull the master cylinder. Mine had an aftermarket one fitted, which I wanted to replace with a genuine AISIN one:

Pretty simple, two flared brake lines, two bolts. Earlier models have four bolts. Same dif. Here's the nice shiny new one:

And for the final word on DOT3 vs DOT4, which didn't exist when the 80 first came out, check out the cap of the new genuine part from Toyota, same part number as the original:

Dot4 is retroactively approved by Toyota guys.

 

[DivByZero]

Time to swing back around to those calipers. So, here's where I'll get controversial. A lot of people here on MUD, when I searched the forums, said to get remanufactured calipers. A lot of people also said, don't split the front calipers. I think that was perfectly sound advice in the past. Not anymore. Our rigs are now 30+ years old in most cases. Increasingly, we can't just rely on easy availability of off the shelf spare parts, and/or local workshops with specialist knowledge about our rigs to solve our problems. We have to become the specialists and solve our own problems, which is, what I believe this forum is about. To that end, I'll be showing you how to fully rebuild your own brake calipers. There's nothing magical about calipers. We talk about rebuilding our own engines and transmissions here. A brake caliper is much simpler, and you have no guarantees that a remanufactured caliper you buy from elsewhere has been done properly.

So then, let's move on and tear down these calipers. The rears are the simplest, let's start there. First, separate the two parts of the caliper. The rears have sliding pins and a single piston. Simply pull the two halves apart to pop the slide pins out. I took a photo of this, but it was super blurry so I'll leave it out.

Next step is to remove the piston from the caliper. The service manual calls for using compressed air. That seemed excessive to me, and I was able to pop the pistons on the rear caliper using a compact bike pump in a gentler manner, just by jamming the pin into the inlet slot on the copper bolt and wrapping a glove around the area to somewhat seal it:

With the piston out, I stripped everything else off, and put it in the parts washer:

In reality, I'm not planning on reusing anything here apart from the caliper. Repeat now for the other rear caliper.

After a bit of a scrub and wash, they're still super grungy. Getting these nice and presentable is going to take some work, which I'll go into soon.

Now let's move onto the fronts:

Super crusty. The fronts have four pistons, two on each side. There are no slide pins. The pads are suspended on a set of pins that are held in by a small clip (already removed in the above pic). Go ahead and take off the pins, and remove the stack of pads and shims:

This is not in good condition. Here I've taken off the rubber boots on one side, and dislodged the metal spring clip on the top right to illustrate how it retains the boots. You can see the corrosion I had here below the boots on the pistons. Now I had to pop these pistons, and they were stuck hard. I abandoned the bicycle pump, and broke out my compressor I use to pump the tyres on the trail:

This is where I got a bit creative. These pistons were stuck, and there are four of them per caliper. Some pistons shifted easier than others. What I did was to break up an old wooden coat-hanger, and used it to selectively lock 3 of the 4 pistons, so I could target the air pressure against each of them individually. Once a piston had "popped", I could insert it back in again gently until I'd popped all of them. I used an old torn valve stem to direct the air, pressing it against the inlet on the caliper:

Using this method, I was able to remove all the pistons. In my opinion, it's best to do it when the caliper is intact rather than after you split it, so you only have one air pathway to manage. Once you pop a piston, you can work your way around to each following one by pressing the air against the internal passage to each successive piston. Pop them all first though, they'll come out much easier the second time.

 

[DivByZero]

Now it's time to split the front calipers. Why do we split the calipers? This is why:

That needs to be properly cleaned and honed. You cannot do that unless you split the caliper. Some people have claimed that you shouldn't split the caliper, because it's hard to reseal without it leaking. I call BS on that, it's not that complicated. IMO, people shy away from splitting the caliper because Toyota don't give a procedure for doing it. And why don't they give a procedure for it? Because they don't make them. These calipers are made by Sumitomo, and Sumitomo seem to have a long standing policy of not supplying service information for their calipers. Toyota buy them assembled, and assembled they remain. How do I know these calipers are made by Sumitomo? Because their logo is cast into them:

Sumitomo brakes are also used extensively on Nissan vehicles. If you cross reference, you'll find a lot of good and very applicable guides from other people on rebuilding very similar brake calipers, like this one:

240Z: The guide to 240Z Sumitomo MK63 / FIA / Competition / NISMO Brakes - JDMjunkies.ch

My knowledge post this time is about the optional Sumitomo “MK63” / FIA / Nismo brakes. I chose this topic, because people often contact me to ask about these, and i thought it might be helpful to some of you. This post is focussing on the Nissan / Datsun S30 chassis Sumitomo MK63 brakes, but...

www.jdmjunkies.ch

You'll also find YouTube videos and the like.

So, we need to split the calipers. Don't worry, it's not that big a deal. To do it, take out these four bolts:

I used an impact wrench. Hit it with a few ugga duggas and they should break loose. Now pay attention. Between the two halves of the caliper, there are two small rubber seals, one on each side where the caliper halves join:

These are called "channel seals", aka crossover seals, bridge seals. Before you hit these calipers with any solvents or do anything else, take these channel seals out, and put them in a zip lock bag in a safe place. We'll talk more about these later. It's a whole thing.

And now, stick it all in the parts washer:

Go ahead and do the other front caliper now. After a bit, you should have something like this. Keep things laid out neatly. You should always know which caliper comes from which wheel, and you must always, always ensure your split calipers stay together as a matched pair. I laid my parts out like this:

In my case, the piles at the top and bottom rows were parts I intended to dispose of. Only the calipers themselves and the hardware next to them was being kept.

Now begins the most painstaking part of this process - parts cleaning. Your brake calipers have 30 years of muck and dust and brake material ground and baked onto it at high temperature. There is no magic solvent or process whereby you can just throw these parts into a vat for an hour and they come out like new, at least not that I know of. Cleaning this up means getting your hands dirty.

I have a two stage process for this. First up is a run through the parts washer. I run my washer with low odour turps, which does a good job of cutting through grease and grime, without being harsh on any parts. It will swell rubber though, so don't put any rubber in that you need to keep, and definitely not those channel seals I pointed out above. The picture above on the cardboard shows after the parts washer run through. After that, for this kind of fine work, I prefer to turn to my trusty dremel, with a flex shaft:

What you want are mini copper wire brushes like you see above. Actual copper, not steel wire painted yellow, which seems to be so common. Copper is critical, as it's softer than steel, so you can grind it against the steel surface and it'll remove the dirt without scratching it up. You'll need a ton of them. I got a pack of like 50 with next day shipping off Amazon for like $20. That's fine, as long as they're actually made of copper. The genuine Dremel ones don't last any longer.

Now, a word about safety. I'm not one to bang on about OHS regulations, but I'd like you at this point to consider that a large volume of the material you're about to grind off with a power tool is friction material from brake pads, which isn't the best thing to breathe into your lungs. You're also about to grind a soft copper brush against it spinning at 10-15k rpm, and it will very quickly start to disintegrate, sending tiny metal barbs flying towards you. A metal needle through your retina is sure to ruin your day. Wear a painters mask and eye protection please.

Now, I didn't get great before and after pics here, but basically the dremel takes off the gunk surprisingly quickly, but it'll still take you some time to get into all those corners and nooks and crannies. Make sure you use the fine "point like" copper brushes to get right into and up the screw holes. Clean your hardware too, those bolts that held the caliper together. This will take you hours if you do it right.

 

[DivByZero]

Here's some before and after:

You want to get right up into those cylinder bores too. You won't damage them, give them a good going over.

Now we're going to hone the brake cylinders. I got the finest 3 leg brake cylinder hone china had to offer:

You attach this to a power drill, dunk the stones on each leg into some clean brake fluid, then position it in the cylinder and move it in and out a bit for 20-30 seconds on a slow to medium speed:

This will help clean up the cylinder surface. It doesn't need to be totally perfect, and it's actually ok if there's some minor pitting in parts, like there was on mine. The piston itself actually rides on the rubber seal rather than scraping directly against the cylinder wall, but we want to clean up this surface nicely. After cleanup, you might be able to notice these internal surfaces are actually coated with titanium, or cast out of a copper alloy or something, to make them corrosion resistant. You'll see the distinct yellow tone on the cylinders and at the channels once they're clean:

It's the same thing for the rears. Hone the cylinders, get them good and clean. And run them through the parts washer again, then let them dry.

Now we're going to prep for painting. There's really not much point going to all this effort IMO and not following through with painting the calipers. It'll help preserve them and keep them in good condition for the next 30 years. To prep for painting, I like to use some isopropyl alcohol, and cotton face wipes to clean the surface:

Wipe down every part of the calipers with this and let them dry, probably about 5 minutes. You then need some really good quality painters tape. Best you can find. I paid $20 a roll for this stuff:

The tape is all that stops the paint from getting where you don't want it to go. You want the good stuff with adhesive that's going to work properly, right up to the edge. Now you have the painstaking job of masking. I started with a rear caliper. At first I went overboard, masking every machined surface:

 

[DivByZero]

This however, was definitely overkill. Not only was it too time consuming, it left paint off areas that could really benefit from it. Still, I moved ahead with this one caliper as a tester for the paint I'd just got.

Now, for some reason, there was an apparent drought of black brake caliper paint in Australia at this time. I went to about 7 retailers. People seemed out of stock of just about every brand. I mean, if I wanted bright blue or neon green I was sorted, but I didn't think that would look quite right on the 80. It was a good thing in the end though, because it forced me to look mote closely and take more time selecting a paint. In the end, I got this one:

Very happy with it. Rated to over 1000c, a high temperature enamel paint. Better than the "brake caliper" paint I was going to get. This stuff needs to be cured at 200c, but that's not a problem here when I'm stripping down the calipers, I just have to bake them in the oven.

So, after applying the spray paint to my test caliper, and being happy enough with how it behaved, didn't run at all, went on well, I had the rest of my calipers masked and ready to go, and set about painting them all:

This makes it sound quick, but the reality is, I had to do one side, let it dry (30 minutes minimum), turn it, do the other side, and that's one coat. I did two coats of black, and one coat of the same stuff in clear because I thought it might give some extra protection and make them easier to clean. With the masking and painting, this took over half a day alone.

With that done though, time to bake them to cure the paint. First, take all that masking tape off, don't want to bake that glue on! I then put them on trays in the oven for an hour at a time at 240c, then turned off the oven and left them to cool inside, as per the directions on the can. This will take the other half of your day.

Pro tip - make sure you get the thumbs up from the misses before using the oven for industrial purposes, or you might find yourself sleeping on the couch!

While paint is drying and calipers are baking, it's a great time to handle another part of this project, the front rotors. I've had these sitting in the garage for some time now, time to install them:

Now replacing the front rotors is non-trivial, as the rotors are mounted to the back of the hubs, so you have to pull your front hubs to change them out. Let's get into it. Here's one of my front hubs. This is a HZJ80 with the manually locking hubs, so it's slightly different to the ones people state side will be familiar with:

First step is pulling the locking hub. Make sure it's in the unlocked (free) position, makes it a bit easier. Take off the six bolts, and set the locking hub aside:

 

[DivByZero]

Now is the best time to take the snap ring out that's on the end of the CV. Didn't take pictures, but you need some snap ring pliers. After that, you'll want a good brass hammer and drift, like these:

Remove the six hub nuts, then wail on the studs with the drift to pop the cone washers. That will allow you to remove the flange:

From here, you want to be careful. I'm not planning to do a full rebuild of the hubs right now, I just want to change out the rotors. Make sure you have clean gloves and a clean work area. We want to avoid contaminating the wheel bearing grease, because the plan is to put this all back on without repacking the bearings.

Now, use an appropriate socket for removing the large nuts. I have this socket I modified for doing front or rear wheel bearings:

We're about to take the preload off the wheel bearings. After this, we need to be prepared to re-seat the bearings and set the preload again. Go ahead and remove the two locking nuts and star washer. You'll need to bend the tabs of the star washer to unlock the nuts.

With the locking nuts removed, you can now carefully slide the entire hub assembly, with the rotors attached, off the spindle:

Now I'd already removed the six bolts attaching the rotor to the hub at this point. If you haven't, go ahead and get the impact wrench and rattle them off. At this point, you'll probably find the rotor and hub are stuck pretty solid to each other. Mine was stuck firm on one side, not the other. What I did at this point was get a pry bar and worked my way around levering it off:

 

[DivByZero]

Fitting the new rotor on the hub is now pretty easy. If you need to, some gentle taps with the brass hammer will help seat them together without damaging the rotor:

From here, it's just reassembly. Assume you'll contaminate some of your wheel bearing grease along the way, and prepare to have some clean stuff to apply when you wipe away contaminated bits. I use this stuff from Timken for my bearings:

Apply the wheel bearing grease as required, and use whatever school of thought you subscribe to in order to set your bearing preload.

Afterwards, clean up all the grease off the rotors with a good brake cleaner. I use the Bendix stuff. Oh, and pro tip, to torque your bolts while the locking hub is off, lock your rotor by sticking a prybar in one of the cooling channels of the rotor to stop the hub from spinning:

You can't torque those hub nuts after you put the locking hub back on with the part time models, as the aluminium housing gets in the way.

And that's the rotor replacement. Repeat for the other side.

Another thing you can do now while you're waiting on the caliper paint is change all your soft brake lines. There are six to do on the HZJ80, one for both the front and rear axles, and one for each wheel. There are only two things to do for each hose, a nut to remove on one end, and a clip on the other. The clips will probably be frozen in place pretty good. To free them, I soaked them with some penetrating lubricant, then pryed them with a screwdriver from side to side first to break them free. After that, you can lever them out with some effort, or work them side to side and up a little each time:

On the other end, you'll.be using either the 10mm flared nut spanner, or a 17mm open ended spanner. Getting them out isn't particularly tricky, but it takes some rolling around under the vehicle to get the ones connecting to the front and rear axles.

After I was done, I laid out all the old and new hoses side by side:

I know some people add extended brake lines to their 80. Now would be the time. I just ordered a set of stock hoses. I have a 2" lift on my 80, the max legal lift in Oz without an engineering cert, and from looking at the hoses, I felt there was plenty of length and saw no point in extending them. Then I found that a PO had extended one of them already, hence why I thought the stock lengths were fine. The one going to the rear axle wasn't Toyota genuine, it was an aftermarket hose with a longer length:

I tracked it down online and ordered another one. It was the ideal length for my 2" lift, was well made, and I didn't see an option for Toyota that was suitable for that hose which wasn't excessively long.

ADR approved extended Brakeline Toyota LandCruiser 80 105 Series 2-3" lift

Rubber Extended Brake Line Front or Rear ABS for Toyota Landcruiser 80 & 105 Series 2" 3" inch lift ADR Approved - Road Runner Offroad

www.roadrunneroffroad.com.au

 

[DivByZero]

Using new clips too, I went around and put all the various hoses in:

One of them however, caused me some trouble. It appears the brake line to the front right wheel had been over torqued in the past. Someone had overtightened the nut, causing the tip of the hard line to flare out, making it impossible to reinsert into the new hose. I solved this problem by breaking out the dremel again with an abrasive wheel to shave off some of the excess flared surface:

This fixed the defect and allowed me to easily push the hard line into the new brake line screw fitting, when this flaring had been stopping the threaded part of the fitting reaching the threads on the hose.

I now took care of the LSPV. I had a brand new shiny one ready to install:

One thing though, that notched fitting on the bottom needed to be rotated to match the angle of the arm. You don't need to mess around with that giant nut on the bottom, there's a small snap ring at the base you just remove, then you can rotate the fitting to the right angle:

Now it's time to reinstall. With new hardware, to make life a little easier. I also have the full boot service kit here, which contains the small metal locking ring that holds the rubber boot to the valve, which is good, because my one was in a sorry state. I decided not to do a rebuild of the arm today though, and just swap over the valve:

But I got a bit rough yanking the boot back over the valve body and tore it. Oh well, that's now a job for another day, I've got the boot service kit for that. I eyeballed setting the height of the valve to the marks of where it sat before, and tightened up the brake lines using the flared nut wrench. I'll be checking proper calibration of this at a later step.

 

[DivByZero]

Now it's time to install the new master cylinder. I got caught out here. I'm pretty careful to check the parts catalog in detail when I'm figuring out what I need, but there's an error in the parts catalog. The master cylinder has a rubber boot on the end of it that fits inside the brake booster. You can see it here on the old master cylinder:

It does not come fitted to the new cylinder:

This is the kind of thing you'd expect to notice in the parts catalog, but Toyota stuffed up. This boot is listed in illustrations for earlier 80 series models with the 4 bolt brake booster, but when they intoduced the 2 bolt version they changed the parts catalog image, and they left off this rubber boot entirely from the illustration and parts list, but it is very much still present and required. For 80 series vehicles after 94 though, you won't find it in the catalog. The part number is 47265-20050. Not having this part on hand, and with none in the country after asking at the dealer, I opted to reuse the boot from the old master cylinder and proceed.

For some inexplicable reason, I didn't take a picture of the new master cylinder installed, but I'll add one in a day or two.

At this point, the master cylinder and LSPV are installed, all the soft lines are replaced, the calipers are cleaned and painted and waiting reassembly, which is our next step. Before we can do that though, we need to have a word about channel seals.

Channel seals are absolutely critical, and quite specific. If you look at the two halves of the front caliper here, you'll see that one side has a recess for the channel seal to fit into, while the other side is flush:

Brake fluid passes through those passages on each side of the caliper, under high pressure. There is no other gasket or sealing surface of any kind that prevents the brake fluid leaking out of the caliper. It isn't the clamping force of the bolts that does this job, the bolts are just there to hold the two halves together, it's the channel seal that contains the brake fluid.

So it stands to reason, you'd want to replace these right? Problem. You can't get them. Remember, Sumitomo manufactured these, and supplied them to Toyota as a sealed unit. There is no Toyota part number for these seals. They aren't listed in the parts catalog. They don't come in the caliper rebuild kits. You also can't just buy them off the shelf. This is not a normal o-ring. Not at all. This is a quite specific square cut rubber seal. The fact it has those flat edges is critical. If it had a rounded edge, as the brake fluid passed through this passage, under pressure the fluid would have leverage to compress the edge of the seal. Over time the rubber would fatigue from the compression cycles, and the fluid would be able to get over the top of the lip and start leaking out the sides of the caliper. With the flat edge, sitting flush and under compression to the top and bottom edges of the caliper, and with a uniform density that means it compresses "flat" rather than ballooning out, what happens when the brake fluid is under pressure is that the channel seal is able to flex very slightly outwards towards the edge of the inset ring in the caliper half it sits in, where it stops, holding back the pressure. There's no purchase for the fluid to squeeze around the seal.

Here's a look at the channel seal from the front caliper. There are two per caliper, four per vehicle. I got a digital vernier caliper to get the dimensions. This is NOT a metric seal, its dimensions are imperial:

That thickness shot is metric sorry, apparently I forgot to take one in imperial once I figured out the units, but the dimensions are this:
OD: 0.5in
ID: 0.34in
Thickness: 0.075in

OK, so we don't have a part number, but we have its dimensions. There's gotta be a source for these, right? It's just a 2c part, a nothing rubber seal. Thus began my quest to find new channel seals.

My first stop was just the good local parts store. I knew they wouldn't have it, but the idea was to find out where might. This was when I first found out how specialised this area is. Square cut rubber seal, the only place they thought might have a shot is a specially brake rebuilder. They gave me the names of two good ones in the Sydney area. Not many of them around. I called them up, and described what I was after. This is when I learned the name "channel seal", and a fair bit about how these brake rebuilders operate. This is what they told me:

They get the same kind of brake rebuild kits we can buy. There's no secret suppliers or special sources. If they were rebuilding this caliper, they'd reuse the channel seals. If one was damaged or lost, they'd substitute with the best match they could find. Where do they get their substitutes? Other brake rebuild kits. These channel seals have no standards. No proper manufacturers or suppliers. They vary greatly from one caliper brand to the next, and they vary greatly within caliper product lines from the same manufacturer. Some vendors supply them in rebuild kits, some don't. Some aftermarket kits include seals when the genuine ones don't. None of the suppliers give dimensions of the channel seals, and there's no database of this stuff. These brake rebuilders just have some cardboard boxes filled with bags of these things, mostly from kits when they choose not to replace the originals, sometimes ordered as numbered parts for brands that make them available, wherever. Both of them did a rummage for me. One of them didn't have anything close. The other had one that was close, so I set off to grab them, and picked up six of these:

Unfortunately, although the measurements were within tolerance, I found that only one side was square cut. The other side had a bevel, presumably to fit a recess in the caliper it was designed for:

I felt this recess would compromise the seal and make leaking more likely, so I didn't go with this seal. These were my only two sources in the city though, and neither of them had these seals on hand, or any connection to get them for me. From here I looked online, and found one promising looking source from a US seller on ebay. I didn't think they'd arrive in time, but as it turns out my family all got hit with covid, and by the time we were well again they arrived.

 

[DivByZero]

I was not happy with these seals. The original ones in the caliper had a nice smooth finish, as did the ones I picked up locally. These had a really rough outer edge with lots of micro tears in the surface. I wasn't comfortable these seals would stand the test of time, so I opted not to use them.

I actually have another set of seals on the way, for an MG brake caliper, which based on dimensions might be a good fit. I'll update on them when they arrive.

At this point however, I needed to get my brakes back together. The existing channel seals looked in very good condition. They've been in a permanent bath of brake fluid for 30 years, and seemed perfectly pliable with no defects. While putting 30 year old rubber back in my calipers gives me pause, the fact was based on what I could access, the original seals were preferable to the alternatives I had on hand. If we can find a source for new channel seals that fit these calipers however, that would be best.


Now, resolved to reuse the channel seals, it's time to talk about bolts. The front caliper halves were secured with four M10x1.25 bolts:

What do we know about these bolts? What are the grades? Torque specs? Do we use loctite? Are they single use? You'll find nothing in the Toyota service manuals about them. The calipers were supplied as an assembled item by Sumitomo. Sumitomo haven't made any of these specs available. We have to figure it out ourselves.

First of all, let's be clear about one thing - these are not single use bolts. Single use bolts are single use because they're Torque-to-yield, or in other words, stretch bolts. These bolts have a section on the shaft narrower than the thinnest diameter inside the threaded portion, so that when you torque the bolt past the yield point, that thinner section of the shaft stretches, without the threaded portion stretching, which would compromise the clamping force. Simple visual inspection shows these are not stretch bolts, as there's no narrower section on the shaft for the yield to occur outside the threaded portion. Not being a stretch bolt, it means we can reuse them.

What is the torque value though? Well, we don't have official specs. We could work it out based on the bolt grade though. OK, what's the bolt grade? We could look at the standard Toyota bolt identification chart:

A normal recess bolt with no mark on the head, that'd be class 4T. At 10mm diameter with a 1.25mm pitch, thats 19 ft/lbf, right? Not so fast, these bolts weren't supplied by Toyota. This caliper was manufactured by Sumitomo and provided as a sealed unit. These bolts don't follow Toyota identification rules. And no, Sumitomo don't publish bolt identification information or torque specs. I'm sure these bolts are NOT class 4T though, they'd by higher for sure. Using standard grades, they're probably at least 8.8, which would mean a torque spec of around 42 ft/lbf. Hard to say for sure what they are though.

This again was something I talked to the brake rebuilders about, to see what they did. Again, no magic rules. They just get the same rebuild kits we get. The way they operate is this - if the kit comes with bolts, they replace them. If the kit doesn't come with bolts, they reuse them. Without torque specs, they use their judgement. Good and tight is the rule.

One last related question - loctite, or no? The rebuilders have the same approach here. If it looks like loctite was used originally, they use it. If not, they don't. On the pictures above, to my eye I thought there was loctite residue, that white gunk. Rebuilder agreed. No idea on the colour of the loctite though, so again, using judgement.

Based on all this, I made the following judgement call: Torque the bolts to 45 ft/lbs. Red loctite:

This is breaking one of my cardinal rules - never use red loctite on a vehicle. In this case though, I believe it's the right call. We don't know the original torque specs or loctite grade. I've played it safe with the torque specs. At 45 ft/lbs, which is probably closer to 52 ft/lbs for a dry bolt (no loctite), this is about as much as I'd push it without knowing the bolt grade for certain. The red loctite on the other hand is going to the upper end, giving maximum locking strength. We don't want these bolts to come off on their own. As for future disassembly, the impact wrench would probably still spin them off, but heating the bolts to 200c isn't hard anyway in this case, with the calipers off the vehicle, and open access at each end of the bolt.

In the picture above, I've already cleaned up the bolts. Hit them with the copper wheels on the dremel again, getting right into the threads and making them nice and clean.

One last thing to fuss over before reassembly. The machined faces of the brake caliper halves. There was some surface rust around the edges:

You see, the two halves don't fit together perfectly at the edges, there's actually some bits that overhang, leaving them exposed to the elements. Running my finger along it, there was a noticeable raised edge. I was concerned that this would prevent the two halves of the caliper sealing together properly, so I broke another cardinal rule - I sanded the machined surfaces, but just at the edges where the corrosion was.

I wasn't trying to make it shine, just feel smooth to the touch. I avoided hitting the main part of the surfaces, and did just enough to make it feel like it'd seal well. With these exposed surfaces, I expect you'd have to do the same with other caliper rebuilds. I planned to hit the exposed parts of this surface with some low temperature curing enamel paint after putting the calipers back together. I can't use the same stuff I used before, because I don't want to bake the channel seals inside the oven to cure it.

 

[DivByZero]

Finally, time to rebuild the calipers themselves. We start by laying out the parts we're going to need:

Not as much as you might expect, just the pistons, rebuild kits for the front and rear calipers, slide pins, and this special rubber grease Toyota call for. Don't substitute the grease, stick with the genuine stuff. The actual product is made by Cosmo.

Now, I bought a full set of replacement pistons. I recommend doing the same. Sure, some of my pistons are still serviceable, and would come up ok with a clean. Some aren't. You won't know what the state of them is until your calipers are disassembled. Better to have everything you need on hand up front, and the pistons aren't too expensive if you order from Partsouq. You can then clean up any of the old pistons you like the look of, and keep them on the shelf for spares in the future. Having a matched set of nice clean new pistons though helps ensure they'll all move smoothly and evenly in your rebuilt calipers, and for this once in 30 year rebuild, it's definitely worth it.

We don't join the front caliper halves back together yet. Far easier to do that at the end after we've installed the pistons. We're going to start with the fronts.

The first thing we're going to do is the piston seals. You'll find them in the rebuild kit, in a little sealed bag with some kind of clear lubricant applied. You'll also find a small sachet of the rubber grease. We don't need that, because we've got the tube.

As per the fsm, we need to apply the Cosmo grease to this ring. I don't trust what's on it in the bag is the same, so I smothered it with the pink Cosmo grease and smeared it all the way around. I also liberally smeared the grease around the inside channel it sits in on the caliper, and up and down the sides of the cylinder wall. I then gently fit the rings into the caliper:

With the rings fitted, time to do our pistons. They come nicely wrapped in the boxes. As per the fsm, we need to smother the sides of these with rubber grease too:

When we insert the pistons, we don't want to push them all the way in at the start. You don't need very much force at all if it's all properly lubed up, the piston will slide in easily. Start by pushing them in gently to about this point:

Now, I saw problems with corrosion on my pistons around this top edge where the rubber boot fits, as well as inside the inside bore of the piston itself. At this point, I liberally smeared rubber grease around the lip of the piston, and inside the internal face of the piston itself, to hopefully create a protective barrier. I then slipped the rubber boot over the end of each piston:

 

[DivByZero]

At this point, in order to secure the boot in place with the locking rings, you need to depress the pistons a bit more. I pushed them down until the outside edge of the rubber boot was about level with the seat on the caliper, then fitted the metal snap rings:

And that's one side of one front caliper. Now you repeat three times for the other half and the other side. Now we get to combine the front calipers back together. First, get your channel seals seated inside the recess. I applied a thin layer of rubber grease to these too:

Now, get your cleaned up bolts and loctite ready:

You apply a small bit of loctite to about 1/3 of the threaded portion in each bolt, maybe about 1/4 of the way around, then immediately insert into the caliper and do up finger tight. After that, go around and torque them to 45 ft/lbs.

Front calipers assembled! At this point, as I spoke about before, I got a can of low temp curing black enamel, and hit up those metal edges you can see where the calipers join. This should help prevent corrosion here in the future.

Now we're going to do the rears. First, as per the fsm, we're going to lube up and install the rubber boots for the slide pins. One boot goes all the way through from end to end. One boot is just a small cap on one end, and a flexible boot on the other. After lubing up the surfaces of the boots well, and smearing grease around the mating surfaces of the caliper, install the boots. Easiest way to get the long one through the caliper is to gently get the end in, then push it through with a slide pin:

With the boots installed, yank that slide pin, and now we'll work on the other half of the caliper.

As per the fronts, you need to lube up the rings and the cylinder, and insert the rings into the channel. I missed taking a picture of this, but it's the same thing as before, just a slightly larger ring. Now it's time for the piston. Lube up the piston really well with rubber grease. If you listen to the fsm here, you'd start by inserting the piston into the caliper, like this:

This is wrong. It'll never work. The guy who wrote this step in the fsm was clearly on something. The rubber boot on the rears has a big lip that needs to lock inside a channel in the caliper. It needs to be seated before you insert the piston, or it'll never be able to make it into the channel. The way to make this work is to lube up the boot well around all the folds, and slip it on the underside of the piston, with the lip that fits into the caliper hanging off the end, like this:

Now you fit the rubber boot into the channel in the caliper, and slide the piston down into the caliper until the boot seats into the groove for the piston:

Make certain you haven't got the boot pinched or rolled anywhere. Spend some time to carefully inspect it and work around the edge of it with your finger.

 

[DivByZero]

Now I got a bit slack at taking pictures for this next part, but suffice to say, it's time to install the bleeder valves into the front and rear calipers, fit the inspection plate cover thingamajigy on the rear calipers, reusing the cleaned up old hardware since it's NLA, and installing and torquing the slide pins. In the end, it should look a bit like this, ready for the pads to be fitted:

We're going to start with the fronts. Inside the rebuild kit, or was it with the pads? Somewhere anyway, you'll find this metallic goo:

This is a special lube to prevent squealing from your brakes. It's just a small packet, but a little goes a long way with this stuff. The fsm shows just applying it to the inner shim, but I like to put it on several surfaces. First I smear a little on the back of the pads:

Then I squish it through and smear a little on the back of the inner shim:

Then finally I put some on the outside where the shims contact the pistons in the caliper:

With the shims installed on the pads, you now just need to hang them in the refurbished pistons and fit the clips in place. Be careful not to get any lubricant on the friction surfaces of the pads. Change your gloves, and have brake cleaner and wipes on hand to deal with messes.

Pay attention to the fsm at this point. The front pads are directional, stamped with L and R. One side of each has a wear indicator, a small metal strip designed to make that annoying whine when it contacts the rotor, before you grind your pads away and wreck the rotors. The fsm shows the direction this wear indicator needs to face. Make sure you understand the orientation of the pads to the caliper, and the caliper to the wheel, so you get it the right way around. After you've hung and locked the pads, it should look a little like this:

Much prettier than where we started:

Repeat for the other side, and you'll have the front calipers ready to install! Now, onto the rears.

The rears have a fitting kit and a shim kit, as well as the pads themselves. These pads are not directional like the fronts, but when you fit the shim kit, you make them directional based on the side you fit the wear indicators to. Like the fronts, check the fsm, and make sure you understand the orientation of the pads to the calipers, and the calipers to the rotors, so you get them the right way around. In the picture below, I've fitted the wear indicators to the sides of the pads. Here I used a bit of that leftover metal grease on the back of the pad, then on top of the shim where it contacts the piston. Note that only one pad per side has a shim or contacts a piston, due to the sliding pin design of the rears:

 

[DivByZero]

I didn't get a picture of it, but you need to snap the slide plates from the fitting kit into the caliper bracket now. There are four per caliper. Make sure you orient the tabs on the clips so they face outwards, away from where the rotor will be, then gently fit in the pads:

We don't put any lube on the slide plates from the fitting kit. We don't want it to attract dust and prevent the pads sliding smoothly, we want the surface clean and free.

Now do the other side, and you'll have four shiny calipers with pads ready to install:

So, with cleaned up bolts you removed before, let's go and mount all four calipers, but leave the brake lines disconnected for now:

Make sure you torque all these bolts properly to spec. 78 ft/lbs wasn't it? Do this properly, you don't want your calipers coming lose. Also note that the lower bolt on the rear calipers can be a pain to get a socket into. I used a shallow socket and my more compact torque wrench. If you don't have the right tools, I'd suggest buying them so you can torque these bolts right.

And on that note, a quick word about bolts. Never trust hardware someone else may have messed with in the past. Here's what I found on my front left caliper:

The bolt marked with grade 11 is standard Toyota. The other bolt is not, and it's only grade 8.8. It's unsafe to torque the 8.8 bolt here to factory spec. It's unlikely the original broke, more likely a previous owner or mechanic misplaced the bolt, and grabbed what he could find that'd fit. I have a spare front diff assembly complete with brakes, so I nicked a mounting bolt from it and used it to replace the dodgy bolt. Check your hardware as you go, make sure it's right.

 

[DivByZero]

Now we're up to bleeding the brake lines. Right now you should have an empty master cylinder, and four brake lines dangling next to the calipers. Next thing to do is go back to the LSPV and crack open the bleeder valve. Remove the small rubber cap and place it aside. Use a 10mm socket or spanner. You only need to crack it half a turn or less, you don't take it out. We just want to open the valve to let air/fluid flow out.

Now we go to the master cylinder to fill it up. I use this dot 4 brake fluid. I went through two doing this process, and cracked the third. Do NOT reuse an open container. Get new sealed bottles. Brake fluid absorbs moisture, you don't want to be using an old bottle that brings a lot of water into your nice clean calipers.

Pull the rubber cap off and fill her up. And keep filling. Those lines downstream are open to air. What we want to do here is flush the air, moisture, and any old gunk out. That's why we don't have the calipers connected yet. We want to push that stuff out, not into our calipers. You'll probably find after filling the reservoir, the fluid doesn't move very much. This is where it's easiest to rope in a helper who can hop in the car for you and press on the brakes when you ask them to, which is what I did. Alternatively, you can get one man brake bleeder kits, but they're a lot of messing around IMO.

What I did here was start the engine, then got my helper to pump the brakes on request, while I stood by the master cylinder emptying brake fluid into it as it was forced out by the brake pedal. After a little while, you'll start to see brake fluid pour out the front right brake line next to your leg. When not pumping the pedal, it should be a slow trickle. This is where you need new shiny copper bolts and washers. Note, these must be new, don't reuse:

You'll need one bolt and two washers per caliper, so twice what's shown here for all four. You put one washer on the bolt, then you put the bolt through thr banjo fitting on the brake line, then another washer on the other side to seal the face against the caliper. Fit the line and torque to spec:

You now need to repeat this process for the front right left wheel. Each time, make sure the brake fluid starts coming out before you fit the line to the caliper, so you know the line is fully flushed of air and muck. Keep heading back to the brake fluid reservoir to top it up as you go, you don't want air to be sucked into the lines at this point, or you'll have to start the bleeding process over again.

After the front right caliper is done, you should find the brake fluid coming out of the LSPV bleeder valve while your helper pumps the brakes. Ideally mid pump, while brake fluid is actively spraying out, tighten the bleeder valve back up and put the cap back on. Now continue to the rear calipers until all the brake lines are done.

OK, you're not finished yet. You bled the brake lines up to the calipers, but the calipers themselves are still full of air. To fix this, go one caliper at a time, remove the rubber cap, and crack the bleeder valve on the caliper. Just like the LSPV, get your helper to pump the brakes, and when that brake fluid is shooting out clear and steady without bubbles, tighten that valve mid stream to seal it off, and replace the cap. Do this one caliper at a time, so only one bleeder valve is ever open at a time.

After all this, your brakes are fully bled, and should be ready for testing and bedding in. There's one more step we're going to do though, and that's calibrate the LSPV. There are procedures for doing this in the fsm, which call for a $1000 SST:

This SST is just a hydraulic pressure gauge. Save yourself some cash, and buy yourself the finest pressure gauge china has to offer, straight from ebay:

What you have here is a pair of pressure gauges, with adapters that allow you to fit the calipers by unscrewing the bleeder valves. Take an old bleeder valve and match it with the adapter to use, in this case number 5:

There's a pair of adapters, for the pair of gauges. What we need to do is remove a bleeder valve from one front brake caliper, one rear brake caliper, and fit these pressure gauges in their place.

It was at this point I noticed this:

 

[DivByZero]

Chinese quality control at its finest. The gauge works, but the back plate with the scale isn't anchored to the dial. So using the good gauge, I made some crude marks on the side and improvised:

I now fitted the gauges to the front and rear, and enlisted my helper again to stamp on the brake pedal on demand.

What we're doing is this - the LSPV changes the proportion of brake pressure that goes between the front and the rear brakes, based on the load on the rear axle. You need to know the loading on your rear axle to do this properly. I do, because I've used a public weighbridge in the past to measure the dead weight on each axle. You'll need to do the same to get your axle loading right. With a known axle loading, the fsm gives you the pressures you should see between the front and rear brakes at different pressure levels. What you do is get your helper to stomp on the brakes, and hold it at the right pressure level on the gauge on the front, then you check the level on the rear gauge. Based on whether it's high or low, you physically shift the LSPV up or down on its sliding bracket to adjust the proportion of braking that goes to the fronts vs the rears.

I didn't get any pictures of this process in action, because it's hard to show, and I lucked out - the old position I set the LSPV to was correct, and my pressures tested in spec on first measure. I'll be repeating this again soon though when I replace that LSPV boot that I tore.

When you're done calibrating the LSPV, unscrew the pressure gauges one at a time, and while your assistant pumps the brakes, replace and seal the bleeder valves to the calipers again. Make sure you're topping up the brake fluid in the reservoir as you go!

Now get your brake cleaner, clean up all the brake fluid and grease, paying special attention to the surfaces of the rotors, and replace your wheels. Top up your brake fluid to max and seal the cap. Your car is now back together!

At this point, you need to carefully test your brakes. Start by making sure they work at all, then proceed to drive like a moron on some quiet back streets close by. Start with some gentle braking, then increasingly get more aggressive. Work up to accelerating and slamming on your brakes at speed. You want to help your brake pads bed in, and you also want to make sure the brake pedal feels right, not spongy, indicating trapped air, not staying soft and going to the floor after pumping it, indicating a leak. You want to make sure the car doesn't pull violently to one side or the other, although it may pull initially as you first start before all the brake pads are bedded in. After a bit of stupid driving and slamming on brakes at random, come back home, visually inspect for leaks, and if all is good, clean up and rest.

 

[DivByZero]

And that is that! This documents my brake rebuild. I'll follow up here with any developments, and when I replace the LSPV boot I'll document that here too. Hope this info helps someone.

 

[AcroSteve]

Outstanding. Simply outstanding, sir.

One question on the LSPV... is there a way to test them? Did you suspect issues with yours, or just replacing due to age?

 

[DivByZero]

Outstanding. Simply outstanding, sir.

One question on the LSPV... is there a way to test them? Did you suspect issues with yours, or just replacing due to age?

The fsm gives the testing procedure for the LSPV. The process is using the rear axle weight, and measuring the relative pressure values at the front and rear calipers with the pressure gauges, as I talked about briefly at the end of my posts above.

I didn't suspect problems with mine, but I simply replaced it because I figured at 30 years it had done its time. The old one is going into storage though, as a potential spare for refurbishment if I need it in the future. If your LSPV passes testing though, it's still doing its job. The fsm describes how to determine if the LSPV is bad based on the values you get back during testing.