100% new brake system 0% pedal

sloanstavern

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Okay guys time for a sanity check. While I realize I have the incorrect wheel cylinders and also appear as the true factory replacements for this unique beast are not available. So I went back in the shop to try this test please let me know if my reasoning is flawed

1. When I isolated the adjusted rear brake circuit perform nicely firm pedal did not need to pump.
2. I crimped off the rear bra hose and focused on the front circuit.
3. I removed the drums and visually set the front and rear cylinder on both wheels to the same point of extension roughly 5 thread counts.
4. I installed the wheels and tighten them down with Lugnuts then started tightening the front and rear cylinder on each side to the same number of clicks-first by Titan in the front cylinder and tell I felt good resistance, then the rear cylinder the same number of clicks until the wheel could not be turned by hand
5. Then I would pump the brakes vigorously go back out and check the wheels if they could turn by hand I repeated if they would not turn by hand then I considered those shoes fully extend it.
6. I did that to both front wheels then compare the measurement of the brake pedal bottoming out versus when I started and the value have not changed.

By my reasoning if the shoes were truly extended fully and the rear brake circuit was isolated and hydraulic fluid cannot be compressed in there must be air in the front circuit somewhere that I just haven’t gotten yet
 

sloanstavern

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Before I waste any more fresh brake fluid I’m really trying to get my brain around what law of physics forces the air out of these cylinders. Both cylinders are mounted vertically and the fluid entry and exit point is midway on a cylinder. By design that’s gonna leave an air bubble trapped at the top Of each of the four cylinders I’m wondering if bench bleeding is the best path forward
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Okay guys time for a sanity check. While I realize I have the incorrect wheel cylinders and also appear as the true factory replacements for this unique beast are not available. So I went back in the shop to try this test please let me know if my reasoning is flawed

1. When I isolated the adjusted rear brake circuit perform nicely firm pedal did not need to pump.
2. I crimped off the rear bra hose and focused on the front circuit.
3. I removed the drums and visually set the front and rear cylinder on both wheels to the same point of extension roughly 5 thread counts.
4. I installed the wheels and tighten them down with Lugnuts then started tightening the front and rear cylinder on each side to the same number of clicks-first by Titan in the front cylinder and tell I felt good resistance, then the rear cylinder the same number of clicks until the wheel could not be turned by hand
5. Then I would pump the brakes vigorously go back out and check the wheels if they could turn by hand I repeated if they would not turn by hand then I considered those shoes fully extend it.
6. I did that to both front wheels then compare the measurement of the brake pedal bottoming out versus when I started and the value have not changed.

By my reasoning if the shoes were truly extended fully and the rear brake circuit was isolated and hydraulic fluid cannot be compressed in there must be air in the front circuit somewhere that I just haven’t gotten yet
@sloanstavern I feel your pain here, but I don't think you are fully extending both brake shoes. When learning how to work on these old brake drum designs with two wheel cylinders per wheel I spent a LOT of time looking at it in frustration trying to figure out how to get them tight. My wife, who is mechanically gifted and also works on these rigs herself is who figured it out. The ONLY way to know if both brake shoes are tight enough on one wheel is to adjust the two wheel cylinders INDEPENDENTLY. Each cylinder on the same wheel needs to be adjusted out so that it alone will lock up the entire wheel, then back that cylinder off ONE click at a time until you can barely rotate the brake drum by hand. There should be a ton of drag. Go back and re-read my post on adjusting the cylinders. Its a subtle difference to how you are doing it, but it's a critical difference to achieving a firm pedal. Hope that helps. Good luck.
 

sloanstavern

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Thanks, I appreciate the feedback I really do. My goal at this stage is to confirm if I’m chasing air in the system
I did adjust each wheel cylinder independently and buy equal amounts with its mate. And brought all of them to the point where the wheel simply will not turn at all. The purpose was to determine if there’s any room for the hydraulic fluid to be moving by my reasoning there should not be.

I’m not trying to adjust them for driving I’m trying to get them all fully extended to test my theory

Back to the air in the system issue with four vertically mounted cylinders, and each has the fluid entrance and exit point at the midpoint of the cylinder how does that air ever get out🤔
 
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FWIW I think the plug you refer to is for a "Low Fluid warning" but it may very well be a stop for the piston in MC.
I realize the small WC may be hard to find ( Mudrak or Beno) but that seems to be the problem.
The pic of the "T" at frame is not clear , more detail pls.
The brake lines to the frame should land the front port of MC to the T which sends fluid to front left & right soft lines.
The rear port of MC should go to the rear of truck on passsenger side to rear axle soft line.
Your issue with bleeding, that is why I said to gravity bleed, vibrate while doing so and you may have to remove the cross over tube, when first wc starts to flow, screw cross over on that wc, wait while it gravity bleeds thru the cross over ( forgot to say, close the bleeder on first wc, but now that I think I dont recall if both front wc have a bleeder screw) anyway, let it come out cross over, make sure bleeder on second wc is open, screw cross over in, wait for that wc to fill, done. Make friends with the barke fluid.
 

sloanstavern

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Thanks PAL
Here are some batter pix
The lines to the MC, could not be crossed to the wrong port.

The lines go across the firewall to psg side, then drop to frame rail. There are two T,s one to the front, one two the rear. Here is where they could get crossed. I plumed it as it came to me, the rear brakes are plumbed to the rear port on the MC.

The MC cap has a low fluid sensor.

At the wheel line feeds front WC then a cross over line to the rear WC which has the only bleeder valve on the wheel.

I did try gravity bleed with vibrate, no joy
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WarDamnEagle

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sloanstavern

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In my best John McClain voice while he’s crawling through the duct work in Yaqui Toma Plaza……..
“ come out to the coast, will restore a non-USA FJ45, have a few laughs”

The hits just keep on coming. So in addition to the soft front brake circuit and incorrect wheel cylinders I also had a mild weeping of brake fluid from one of the four fittings on each front wheel I took the lines out to inspect and noticed each cylinder Will receive a flared line and the other is plumbed for a bleeder valve that explains the weeping…..😳
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If the original wheel cylinders were NLA how did you decide on the ones you have? I was able to figure one of the front wheel cylinder part number. PARTSoug sounds NLA but has cheap aftermarket substitute available if you scroll down a little. I would order aftermarket verses pre 8/80 brake cylinders for your non US import. When I purchased axles from an Australian 84 HJ47RV I then pulled the master cylinder, booster and all the brake lines for it my 65 FJ45 has the old small line single circuit setup. Figure non US import would be easier making it all work. The load sensing valve on the rear axle still not sure if I'll use it.
 

sloanstavern

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If the original wheel cylinders were NLA how did you decide on the ones you have? I was able to figure one of the front wheel cylinder part number. PARTSoug sounds NLA but has cheap aftermarket substitute available if you scroll down a little. I would order aftermarket verses pre 8/80 brake cylinders for your non US import. When I purchased axles from an Australian 84 HJ47RV I then pulled the master cylinder, booster and all the brake lines for it my 65 FJ45 has the old small line single circuit setup. Figure non US import would be easier making it all work. The load sensing valve on the rear axle still not sure if I'll use it.
I mistakenly thought an earlier WC that fit the baking plate would work, I was not aware of the difference in bore Diameter.

I see what you mean , if you scroll down there are some after market options.
 

sloanstavern

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I have everything put back together, and hit it hard with an upgraded pressurized bleeder which did take out quite a few bubbles, but still not where it needs to be. I thought I would hit the brakes so to speak and start checking out some low hanging fruit, for one thing I have no idea how many times these drums have been turned according to my book I should have no greater diameter than 11.5 inches or 11.7 inches depending on the application. For the dual shoe , non-USA front I am assuming the 11.7 is correct and these are right at or just over the limit.

Can anyone confirm that spec and interpretion?

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Next up I’ll take a look at the push rod between brake booster and MC, but I do not know what that spec should be?
 
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While I never checked it personally I was told the late model 40 series and the early 79-85 mini truck used the same front knuckles. Each had their own part number and price. Land Cruiser costing more. I do know the L brackets for the transmission crossmember member changed part numbers the same time the five speed started and the crossmember itself changed for better clearance for the longer front driveshaft on the optional H55F five speed. I have L rackets from before and after the change. Those are the same right down to the digits stamped into them. Another thing I have hear is all rear drums post 8/80 on the 40 series and all 60 series are the same part. Because the US never had drums brakes after 75 have no personal experience with those. I do have a 84 front axle off a troopy but because it ce from Australia it's a disc brake axle. Think I would be comparing my front and rear drums. Then see if a 60 series drum would work. I have a 8/80 plus full floater buried on my axle rack. It looks identical to the 60 series rear drum I came across a few weeks back. But didn't have them side by side. Unfortunately your local Toyota parts guy will most likely not have an idea of cross referencing 60 series drums to other models. Toyota's part system is no help. I would be seeing if some 60 series parts would work. I an thinking of converting US model 40 series over 8/80+ full floating rear axles. Those seem more standardized than the early full floater that everything is different than the semi floater of the same time period.

As for turning drum I would let a shop who turn drums look at them. Really can't tell with a ruler. Beside thickness they check out of round.
 

sloanstavern

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I would not rule out pushrod. If your depth is too deep, it’s already pushing the piston part of the way through its stroke at rest because it won’t fully retract. This means you aren’t getting full fluid volume. If the pushrod is not deep enough, a portion of your pedal travel is doing nothing but taking up the slack, so you’ll never get full volume.

Another thing to verify: Are your lines hooked up to the proper port on the master
Did you ever set the pushrod height in the booster? If this is wrong, you can still get a firm pedal but won’t get full stroke if either too deep or too shallow. Then there’s also the pedal to booster length.
You were right. This morning I remove the master cylinder and was able to gently set it aside without disconnecting the brake lines. They make a tool for measuring it but I think I was able to do it satisfactorily with my caliper and some straight edges the push rod from the booster was actually loose and the lock not had backed off as near as I could measure it was a quarter inch or more short of engaging the master cylinder. Based on a quick Google search I extended the pushrod leaving about 20 thousandths of an inch before it engaged.

Fired it up with the new carburetor hooked up the vacuum to the booster and took her for a spin I still need to do some adjusting on the wheels but one press on the pedal and I got nice uniform breaking a world of difference! Thank you so much for the tip that was a lifesaver
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Skreddy

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I hope that does it! So frustrating when it feels like you’ve tried everything with no success.
 

sloanstavern

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Yup this one had me beat… I simply couldn’t believe a minor miss adjustment in the push rod could make such a big difference but you were right man.


In hindsight I think the entire travel of the master cylinder piston is maybe only an inch or so so if you’re off by a3 of an inch that’s a pretty big gap
 
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I read through all this pretty fast, but I did not see it noted. You did discover that the cylinders you were using both had bleeder ports. Each cylinder is unique, they are left and right sided and they have to be in the right spot front to rear on the backing plate. Specter has a nice diagram showing the cylinders, the adjusters go opposite of each other, so that is important. The cylinders only move on one side, so one acts on each shoe. Also I use Sylglide grease on the pistons, and in the adjusters, or antiseize, but it tends to go hard after several years. The adjusters that face up get seized pretty quick because that piece has to rotate in the cast iron cylinder and the rust up depending on your driving conditions. If you drive it a lot, like daily, every 6 months is a good interval to adjust a little, they do wear down, those millimeters add up.

I also noticed your lines, and why the front cylinders both had bleeders. My 73 has a single flex line to a "tee", then a line to each front cylinder and a bleeder on each cylinder. Not sure if yours is wrong, or if Toyota dropped that design for the later drums. My rear drums have the primary line to one cylinder and then the connector line between them with one bleeder. The rear cylinders are smaller bore though.

Also I had to service my front cylinders and found that Toyota changed the bore diameter about three times between 70 and 75, so that adds even more variability to the front cylinders you may have had.

There is also a taper to the slots where the pistons meet the shoes. They are supposed to go a certain way, I can't recall which, but I found I had mine mixed in orientation and did make a difference once I go them all turned to meet the shoes the proper way. I think they actually make the shoes wedge harder during forward braking. Reverse braking is not very good with the drums, just my observations.

A final comment to the group as a hole, the US 4 drum masters have side outlets, would that have been a possible replacement for him? Not sure if the bores are the same as the later model drum master he sourced.
 

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