Brake problems, 4runner calipers and standard master problems?

[Christian]

Update:
For those of you who find this thread searching for possible solutions to your own brake problems, I have the following information:

The combination of the largest of the 4runner/T100 calipers (S13WB castring, 4X45mmm pistons) and the original master works, that was not the problem, it was me who got some lines crossed to the LSPV.
Btw. If you experience problems getting a firm pedal, be sure to bleed the LSVP if you have one, if in doubt, look just in front of the rear axle, if you have a steel rod, about 1/4" thick going from the rear axle to the frame, you have a LSPV, there's a bleed screw on it, the FSM says to bleed it last.

This combination of calipers and stock master will give a longer pedal travel, and ntsqd has calculated the ratio (leaving out the booster) to be 1:70, for his explanations, look on page two.

Thanks goes out to those who helped and supported me in finding my own stupid errors!


Hi all

I have searched and read what I could on the subject, it seems that others have had the same issues, and posted them, but there's no posts on solutions, I hope this ends up with me finding one, so my truck will be on top of it's game again, and others may benefit too, so here goes:


I'll start from the beginning:

I finally did get around to do something about my brakes, after seeing I had cracks in the discs and the pads where worn down.

So I took the plunge and bought and installed the following:

1. 1995 4runner/T100 S13WB calipers with 4 X 45mm pistons
2. New standard discs
3. Hawk LTS pads

Install went fine, I had to do some very minor grinding, but just 1-2mm right on the cormers of the fins.
I went out to bed in the pads, and ended up with hanging brakes!
Well I thought it might be the master hanging, it looked old, and I had a new one on the shelf, so in it went.
I couldn't get a good feel, the pedal was soft, and dreaming of locking up the front? no way!!!

So I bled gallons through the system, but no improvement. Read about bench bleeding the master, did that, I thought the LSPV could be flushed by running enough fluid through it, since the bleeder looked really rusty, but got wiser on MUD, so fixed up another LSPV and installed that, but its not any better, and I'm at my wit's (and search's) end!

But my brakes are still not good!

List of what I've done:

1. Replaced discs (standard 20mm)
2. Replaced calipers (4runner 4 X 45mm S13WB, originally used on 25mm discs)
3. New Hawk LTS pads
4. Bled the system, using "two guy" method, LR, RR, LF, RF
5. Mounted a new master (22mm, 7/8" bore)
6. Bled the system
7. Bled the master
8. replaced the LSPV
9. Bled again, thouroughly! MC, LR, RR, LSPV, LF, RF, LSVP and again at least 5 times, omitting the master.
10. Took the master apart to check it, no issues
11. bled the master again, used 60cc syringe to create a vacuum to be sure ALL air was out of the master, before attaching lines, then bled the rest, LR, RR, LSPV, LF, RF, LSVP and again at least 5 times again.

The pedal feels somewhat like there's still air in the system, but there simply cannot be! It could also feel like there's simply not enough volume in the master to apply enough pressure to make it efficient?
Could it be, that having the 4 X 45mm S13WB calipers just took it over the top? Most 4runner calipers are 4 X 43mm, S12 casting...?

My next step could be to get a new 15/16" master, or maybe a 1", and a new booster, what's the verdict?

 

[Elbert]

no problem with the parts... I have the same thing...4 runner calipers on the front and stock MC (rebuilt aftermarket). Mine works fine.

Have you ever replaced the old rubber brake hoses?

You always bench bled the master cylinder before install.

I've never had a problem with the parts as noted...you need to get rid of those old rubber brake hoses.....Once I did that on my truck...brake performance improved greatly.

I've never understood the guys that seem to be chasing all the different master cylinder configurations and bore size.. I have stock brakes all around, 4runner calipers on front, stock crap on the back, stock master and it works fine.

 

[Elbert]

I chased some brake problems for a while...turned out it was the master cylinder that failed and then the rubber hoses needed replacing (the ones on the calipers and the ones that feed the front and rear axle.

 

[Spike Strip]

Your brake pedal is gonna feel "low/squishy" until you change out the master to a larger bore one, either from a 4Runner or T100. There are a bunch of threads on this where NTSQD has done the math to get you closest to stock feel. I went with a t 1" MC and the pedal is firm. IIRC, 15/16" gets you closest to stock ratio. I had squishy pedal until I changed the MC.

 

[dbleon]

+1... the hydraulic #s have been run before. A search should yield sage advice on this subject. A T100 master from Napa runs $70 IIRC. Worth a shot... and yes replace the lines. Extended SS lines can be had from Napa too...

 

[Tapage]

I went all way up ( 1 1/4 MC ) to all way down .. ending in 1" MC .. overall the most close to stock / firm pedal so far..

 

[Stumpalama]

Also, check to make sure your booster push rod and and M/C piston are properly adjusted, otherwise you may not be getting the full range of motion on the M/C pistons.

 

[Christian]

Thanks guys!

I PM'ed ntsgd before I opened this thread, I think I've read every post he has written on the subject. He is looking in to it, patient and helpful mudder indeed!

I haven't changed the soft lines, I should, but I'm waiting on a tool to make new brake pipes, I know I won't be able to change the soft lines without damaging the hard ones, the connections are badly corroded...

I have checked the pushrod, other connections etc...

So, others have done the same as me, without experiencing the trouble I have, so there's something different...?
I suspect that the combined extra volume needed in both the larger calipers and the old soft lines are the tipping point, making the fluid available in the front cirquit part of the master just not enough... Sounds right to any of you?

Of course I will change the soft lines, but getting the larger master plus the 4runner booster will make the setup almost identical to the setup in the 4runner, exept pedal leverage, so this might be the way to go?
The general concensus seems to be that the 1" master is the best match, right?

 

[60Works]

Also, check to make sure your booster push rod and and M/C piston are properly adjusted, otherwise you may not be getting the full range of motion on the M/C pistons.

This.

I run the 4Runner calipers with a stock 60 MC. No troubles, firm pedal. It does take more pedal travel but it's not excessive.

Is the only trouble you still have is the mushy feel? The method I've used to bleed the MC is to attach fittings with clear plastic hoses curling back into the reservoir. Pump until the bubbles stop. Then pump some more. Once in frustration of unbleedable air, I let a shop pressure bleed from the brakes up. Seemed to do the trick. I've also had a slightly mushy pedal clear and firm up after a couple of days of driving.

It's important to remember that a larger MC will decrease your brake pressure. I wouldn't recommend using a larger bore MC than what Toyota designed for your front calipers. Meaning, stick with either the stock or 4Runner MC. If your system is working properly it will be firm enough.

The push pin from the booster is set with correct throw for the new MC?

Your drums are adjusted properly?

The new calipers don't have stuck pistons?

Replacing the soft lines with SS is a good idea but the old rubber won't cause a mushy pedal. (unless they are obviously leaking anyway)

 

[Christian]

Everything adjustable has been checked...

I've never heard about bleedning the master before I read it here, and I haver seen the plugs and tubes you guys get, we just bleed them through the nipples i believe. Nevertheless I made a master bleeding kit out of two pieces of pipe and some silicone tube, vacuum bled it even, using a 60cc syringe.

i haven't checked wether all the pistons move in the new calipers, that will be next!

SS lines with visible braiding is illegal here, the reason is that the line cannot be inspected for cracks.

Mushy might be an inprecise description, its not springy, it just doesn't press the caliper pistons out hard enough, if i pump it, just before braking, it's fine.

I just don't get it...

 

[60Works]

Since you changed your disks you would have disturbed the wheel bearings. Why not jack the axle and check them for play? It's unlikely, but possible, that loose wheel bearings caused the front brakes to drag. Disks that aren't fully mated to the hub might cause problems too. Did you press the studs with a press,or a hammer, or pull them tight with a lug nut (which can stretch them).

I use a vaccuum bleader and it isn't as good as having someone pushing the pedal or using a pressure bleader. It helps to put some grease on the threads of the blead screw so the vaccuum doesn't pull air past the threads. Some people swear by speedy bleeders. Might be time to invest is a set.

Other than the brakes hanging, it still sounds like an air bubble.

Sorry you're having such troubles. It is a fairly common problem so you're in good company.

 

[Tapage]

note as reference .. my setup chevy 1" MC with front SW13 calipers and rear chevy single piston calipers ..

 

[Slow Left]

Not sure this applies (because I'm not sure you changed out your rear pads), but after I work on the rear drum brakes, bleed, then drive very very slowly in reverse pumping the brakes and it helps set the pads...

 

[Elbert]

its a game changer...in the positive direction to get rid of those old rubber brake hoses.... I been there and its a impressive improvement to your brake system all the way around....night and day difference.

 

[Christian]

Since you changed your disks you would have disturbed the wheel bearings. Why not jack the axle and check them for play? It's unlikely, but possible, that loose wheel bearings caused the front brakes to drag. Disks that aren't fully mated to the hub might cause problems too. Did you press the studs with a press,or a hammer, or pull them tight with a lug nut (which can stretch them).

I use a vaccuum bleader and it isn't as good as having someone pushing the pedal or using a pressure bleader. It helps to put some grease on the threads of the blead screw so the vaccuum doesn't pull air past the threads. Some people swear by speedy bleeders. Might be time to invest is a set.

Other than the brakes hanging, it still sounds like an air bubble.

Sorry you're having such troubles. It is a fairly common problem so you're in good company.

The wheel bearings are fine, the drag was caused by the old master, a previous owner had messed it up, unscrewing the detent screw, thereby scouring the front pistol a bit.
I used my 25T press on the studs, I'm getting older, maybe not wiser, but better equipped!

Everybody else seems to be able to make this setup work, so so should I!

A vacuum bleeder is on the shortlist, but i might just get some of those speed bleeders too, not so much for the valve action, more to be able to see any bubbles I might eventually find. The bleeders in the calipers and cylinders now will let air pass in through the threads, making it impossible too see any trapped air getting out.

Thanks for your help and advice!

 

[Christian]

its a game changer...in the positive direction to get rid of those old rubber brake hoses.... I been there and its a impressive improvement to your brake system all the way around....night and day difference.

I will get around to them too, but a small test having a friend punch the pedal didn't reveal any bulging

 

[Christian]

Some thread mentioned bleeding the master at the detent screw, has anyone done this?

 

[Elbert]

I will get around to them too, but a small test having a friend punch the pedal didn't reveal any bulging

the hoses degrade internally.....you have 20+ year old rubber hoses on your brake system.... Don't judge the integrity of the rubber brake hoses by external appearance. Replace all and move forward.....I though I had crappy brakes and it was just the reality of the vehicle...until I swapped the old rubber hoses.

 

[Christian]

the hoses degrade internally.....you have 20+ year old rubber hoses on your brake system.... Don't judge the integrity of the rubber brake hoses by external appearance. Replace all and move forward.....I though I had crappy brakes and it was just the reality of the vehicle...until I swapped the old rubber hoses.

I know, but changing them means new anchor plates, the junctions on these are bad, so are the anchor plates, and that means new seals in the axles, which means the axles have to be sandblasted and painted, and when that is done new springs should be put on, so the frame needs tlc too, sandblasting, hot zinc spray coating and paint, so new hard lines have to go on too... when all that is done, the new body should be completed too.... Damn, this one is gonna cost me! Well, that's what I get for driving a vehicle that has done +330K miles...

To be a bit more realistic, I have a frame-off resto planned, and i am compiling parts for it, a new body amongst others are in-house... Right now my goal is to make the truck driveable, but changing the hoses will be a PITA with the corrosion on the fittings...

BUT the hoses can't be the culprit in my mind, I can pump the pedal, and get decent braking, that doesn't sound like hoses to me?

 

[Elbert]

do as you wish....my friend who is a 20+ year Toyota Mechanic brought it to my attention, because I had the stock old rubber hoses on my truck and was having crappy brake performance. I"m not saying its a cure all... but its certainly cheap to do and it makes a big difference if the old hoses have degraded internally. I had meant to change the hoses a few times and they just got off my radar screen....when I finally did I could have kicked myself for not doing that a year or so previously. Point is ...you have a 20+ year old machine...if you have to bleed the brakes for anything you might as well take the time to swap the rubber hoses.