Need help with Toyota Brakes!

Charles Sauder

Charles Sauder

Member
Joined
Apr 15, 2020
Location
Boone, NC
At my wits end with these damn brakes. Have to pump the brakes twice to get a firm pedal, and then it stops great. The pedal doesn't leak down as you hold it, but if you let off and wait just a few seconds it will go to the floor. It has mediocre braking power on the first pump. 1986 Toyota Pickup. Solid axle. 3 link w/ hydro assist on coil overs. Chopped and tubed most of the front half and moved the axle forward about 4 inches. When we did that we ran all new "soft" lines from jegs. Since then I have replaced Master (twice) both front calipers, and both rear wheel cylinders. One rear wheel cylinder was leaking slightly and I thought for sure that would fix my issue. Nope. We eliminated the proportioning valve as well. The only original lines on the truck are the hard lines from the master down the frame rail. No visible leaks anywhere. I have the rear shoes adjusted as far out as possible until the wheels became difficult to turn by hand. I have bled and bled and bled, probably have $75 in brake fluid. I bled them in the correct order. No air in the lines, I'm almost sure of it. I did not bench bleed the master but I have never had to before, it seems to be moving fluid well. I have a master for a v6 truck coming, which is an upgrade and supposed to move more fluid, and I will bench bleed it this time. It used to stop great before we did the coilovers and front half, not sure if thats coincedental or something we did. My next move while waiting for the THIRD new master is to first block off the rear brakes, and then the front, at the master, and see if I get a firm pedal either way. I am about to lose my gourd here. Any suggestions would be appreciated.
 

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At my wits end with these damn brakes. Have to pump the brakes twice to get a firm pedal, and then it stops great. The pedal doesn't leak down as you hold it, but if you let off and wait just a few seconds it will go to the floor. It has mediocre braking power on the first pump. 1986 Toyota Pickup. Solid axle. 3 link w/ hydro assist on coil overs. Chopped and tubed most of the front half and moved the axle forward about 4 inches. When we did that we ran all new "soft" lines from jegs. Since then I have replaced Master (twice) both front calipers, and both rear wheel cylinders. One rear wheel cylinder was leaking slightly and I thought for sure that would fix my issue. Nope. We eliminated the proportioning valve as well. The only original lines on the truck are the hard lines from the master down the frame rail. No visible leaks anywhere. I have the rear shoes adjusted as far out as possibe. I have bled and bled and bled, probably have $75 in brake fluid. I bled them in the correct order. No air in the lines, I'm almost sure of it. I did not bench bleed the master but I have never had to before, it seems to be moving fluid well. I have a master for a v6 truck coming, which is an upgrade and supposed to move more fluid, and I will bench bleed it this time. It used to stop great before we did the coilovers and front half, not sure if thats coincedental or something we did. My next move while waiting for the THIRD new master is to first block off the rear brakes, and then the front, at the master, and see if I get a firm pedal either way. I am about to lose my gourd here. Any suggestions would be appreciated.
 

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By removing the prop valve did it remove the ability to “hold” fluid in proportion to the rear? I thought there was a part of the braking system that held a % of fluid so the brakes reacted faster when the pedal was applied. Maybe I’m wrong or have been drinking??
 
^^the prop valve is likely a combo valve that includes a check valve.
Even if there isn’t a combo check you stolll need differential pressure between discs and drums
 
Ron said:
^^the prop valve is likely a combo valve that includes a check valve.
Even if there isn’t a combo check you stolll need differential pressure between discs and drums
Click to expand...
Check valve. Yeah, that’s the term I was looking for. Also, changing the front soft lines are they the same size? Need more fluid volume to fill before actuating the calipers? Reaching now but....

when it comes to hydraulics they are finicky beotches. Brakes or clutches!
 
Chuck, 3.4 Tacoma or T100 Master Cylinder then vacuum bleed everything. I used one of the bleeders that hooks to a compressor and pulls everything through the brake lines rather than pushing from the master essentially flushing the whole system. Only way I could get a good pedal feel in that 85. Did the same when I put it on tons and never fought a brake issue.
 
StretchASU said:
Chuck, 3.4 Tacoma or T100 Master Cylinder then vacuum bleed everything. I used one of the bleeders that hooks to a compressor and pulls everything through the brake lines rather than pushing from the master essentially flushing the whole system. Only way I could get a good pedal feel in that 85. Did the same when I put it on tons and never fought a brake issue.
Click to expand...
Thanks stretch, I'll try that. Did you keep your prop valve or run some kind of check valve to the rear?
 
Charles Sauder said:
Thanks stretch, I'll try that. Did you keep your prop valve or run some kind of check valve to the rear?
Click to expand...

I ditched it and did initially fight some issues with air in the lines. When you T the lines where the prop valve used to be I swear the bubble just sits there. That’s why I vac bled it. After topping off the master the 2nd time a big bubble came out.
 
Is the rear axle original to the 86 ? Shoes and wheel cylinders are different from 86-87 the depth of where the shoe spine fits in the wheel cyl and the actual length of wheel cyl are different, the drums are identical....

ive beat my head on this wall before

1987 shoes see the tabs at top, they are short and fit into wheel cyl ends
B7F53AA5-9BC0-4830-AF72-A589D2375C77.jpeg

image is upside down, but the tabs on the 1986 shoes are longer and the wheel cyl is shorter, if you’re using 87 shoes on 86 wheel cyls....
E30264BE-DBD1-467D-820B-CF73B41C064D.jpeg



I ran into the opposite, using 86 shoes on 87 wheel cyls.....20 years ago.....
 
I am having the exact same issue on a 1985 pickup after unhooking the rear wheel cylinders. If you come up with a solution please share with the class if you don't mind. I have bled brakes till I am sick of it, I have used a vacuum bleeder and the old fashion way with with someone pumping the pedal.
 
Pless said:
I am having the exact same issue on a 1985 pickup after unhooking the rear wheel cylinders. If you come up with a solution please share with the class if you don't mind. I have bled brakes till I am sick of it, I have used a vacuum bleeder and the old fashion way with with someone pumping the pedal.
Click to expand...
Damn sorry for the late response on this. I did end up getting it fixed, the v6 master cylinder and the vacuum bleeding seemed to do the trick for me. I think after removing the prop valve it needed to be able to push more fluid. I'm actually only back here on this thread because after unhooking my rears to do a third, same damn problem !
 
I have been meaning to look this thread up and share what I ended up doing incase of anyone else searching. To put things in context I have larger calipers and vented rotors up front, and the larger IFS rear drums. I finally figured out that a bunch of the crappy pedal feeling that I was getting was because of the rear drums needing to be adjusted out (felt like an idiot). After that the brakes still weren't great, I would have to stand on the pedal to get it to stop and it still had a little more travel and spongy feel than I liked. I was poking around on rock auto and found an FJ80 master for 23.00 bucks so I picked that up and installed it, honestly I can't tell that it changed much. So after doing a little more digging I found out that I had a single diaphragm booster and that a 89-95 pickup booster is a dual diaphragm and will bolt on, so I picked one of those up. I installed it and it made a huge difference in pedal input, I can lock up the rear tires for the first time since I have owned the truck. I still have a little bit more pedal travel than I like, but I think the pushrod on the new booster needs to have the slack adjusted out. I took it to Harlan last weekend and I never got in a situation where I felt like I didn't have enough brakes, where as before I always wondered if I was going to be able to get it stopped.

I can't really wrap my head around the FJ80 master swap, it is a larger bore so it should move more fluid which should equal less pedal travel. But that would also mean it would require more force input on the pedal to get the same amount of pressure at the caliper as the smaller bore stock master. So if all of that is correct what is the advantage of the FJ80 master?
 
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