Brake issue. Anyone getting a solid pedal with FJ80 Master Cylinder and Booster? edit: All Good!! (1 Viewer)

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Hey dudes, and gals,
Just went for the full disc brake conversion and system upgrade.

First easy question:
Is anyone running an FJ80, non-ABS, Master cylinder, and FJ80 Brake booster, and getting a solid pedal while the engine is running???????

The rest of the story...
-New FJ80 non-ABS Brake Master cylinder
-New FJ80 Brake Booster
-New rear discs, using Monte Carlo calipers
-New front calipers, using Wilwood 4 piston calipers. (replaced old Wilwoods)
-new rear proportioning valve.
-all new flex lines except the two front steel braided lines that appear fine.

I cannot get, for the life of me, a solid brake pedal while the engine is running. I will slowly sink to ..almost.. the floor. With engine off, the pedal is rock solid at the top. ..start the motor and it will travel half way down, and slowly sink almost to the floor.

***Big clue***
with the flex lines to the axles clamped off, the brake pedal is solid, with the engine running.

-Bench bled master cylinder
-I have bled the bejezus out of the system, engine running and not. used a brake bleeding container with a check valve. Also gravity bled, trying to get any last bubble out of there. I've put over a couple quarts through there so far...
-Adjusted the pedal for maximum travel.
-Adjusted the brake booster rod to specs. Then adjusted it out further and further, trying to get some pedal. Currently the booster is depressing the M/C slightly at rest. It helped...
-Rotated the front calipers vertically to get every tiny bubble out of there.

It appears the residual pressure valves are working. All brake pads are lightly dragging the rotors and evenly spaced.

Also, about to rebleed the M/C, but hesitant to open the system back up.
Also about to swap the stock booster back in to see if I'm getting too much brake assist.. That's all I can think of right now!

I'm am wondering if the FJ80 M/C is providing sooo much boost the pedal WILL travel to the floor if you stand on it?

So back to my original question.. Is anyone getting a solid pedal while using an FJ80 MC and booster???

Holy cow I'm stumped.

Any help?
Thanks, B.
 
Last edited:

1911

chupacabra
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***Big clue***
with the flex lines to the axles clamped off, the brake pedal is solid, with the engine running.
Then the problem is somewhere between the clamped-off lines and the calipers.

Elementary question, just making sure: did you install the calipers with the bleed nipple up? Some folks forget to do that, and lots of calipers will go on upside down.

Other than that, try a different bleeding method, reverse, vacuum, gravity, a different way/direction than you did before.


Currently the booster is depressing the M/C slightly at rest. It helped...
Don't leave it that way! You pads will be dragging on the rotors and heat up and wear out.

Don't think the master is the problem; too many people (including myself) have had excellent results with it. I guess it's possible yours could be bad out of the box, but if you're getting pressure with the soft lines clamped then that tells me the master is working.

The only unknown (to me) is the 80-series booster. I used a City Racer booster with my 80 master and couldn't be happier.
 
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Do you have a check valve between the booster and the vacuum source. 40 series have the check valve in the booster, and at least my 80 series didn't have an integral check valve.
 
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Thanks a bunch 1911


Then the problem is somewhere between the clamped-off lines and the calipers.

...sure seems to be, but I'm not seeing it...

Elementary question, just making sure: did you install the calipers with the bleed nipple up? Some folks forget to do that, and lots of calipers will go on upside down.

...great question, yes bleeders are at the top...

Other than that, try a different bleeding method, reverse, vacuum, gravity, a different way/direction than you did before.

...I'm going to try more...


Don't leave it that way! You pads will be dragging on the rotors and heat up and wear out.

...thanks. I was trying everything to get a solid pedal. Will adjust back to normal if I get this figured out...

Don't think the master is the problem; too many people (including myself) have had excellent results with it. I guess it's possible yours could be bad out of the box, but if you're getting pressure with the soft lines clamped then that tells me the master is working.

...agreed...

The only unknown (to me) is the 80-series booster. I used a City Racer booster with my 80 master and couldn't be happier.

...good to hear, thank you...
 
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Do you have a check valve between the booster and the vacuum source. 40 series have the check valve in the booster, and at least my 80 series didn't have an integral check valve.
Thanks. Thinking about it, I don't think I have a check valve installed. As soon as I shut off the engine the brake pedal comes up with no assist. I'm sure the pedal would remain depressed if there was a check valve. Thanks for the heads-up!
 
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Do the soft line clamp one axle at a time and see if you can isolate which end is causing issue
 
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Do the soft line clamp one axle at a time and see if you can isolate which end is causing issue
Hi pees.

I wish I had.

I'm pretty sure clamping is bad for the hoses. I clamped the old rubber lines, saw the Master was good, then replaced them with new steel-braided. Then started bleeding everything.

I'm now thinking of swapping on the old "clampable" hoses back on trying to isolate the problem area.
I might do that and while I have it apart again I'll rebleed the Master. (edit: come to think of it, I shouldn't need to bleed the master)

I wish the whole system was clear so I could just see the bubbles!!!!!! This is driving me batty. (it was a short trip) haha

Thanks for the help guys.
 
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BTW, with an 80 booster my brakes take very little force on the pedal to stop quickly.

I tried running for a bit with no check valve... the braking was crap.
 
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swapping to the soft lines to test is a good idea, pita, but nec. Also, were you able to pump the brakes to a hard pedal or did it never get hard , always bleed down ?
 
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swapping to the soft lines to test is a good idea, pita, but nec. Also, were you able to pump the brakes to a hard pedal or did it never get hard , always bleed down ?
It's crazy, the pedal is hard as a rock with engine off. With engine running the pedal sink close to the floor in a second or two. I cannot pump it to a hard pedal, and if anything, it feels like the pedal stays softer once I get it pushed all the way down.

I'm going to try vacuum bleeding tomorrow and see what happens.

edit: I might take it off the jack stands also and see if the braking action offers any more clues.
 
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From that last description it sounds like it’s working like it should
Maybe it is getting so much brake boost it allows me to press the pedal to the floor, it does take some effort though. I'm going to put it back together and see how it drives. It'll be interesting...
Thanks again for the assistance.
 
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Maybe it is getting so much brake boost it allows me to press the pedal to the floor, it does take some effort though. I'm going to put it back together and see how it drives. It'll be interesting...
Thanks again for the assistance.
It’s very possible. With a sharp stab with two fingers mine will lock all four wheels on dry pavement at 30 mph.

usually a press with the big toe is all that’s needed to bring 4700 lbs to a halt. :D
 
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Godwin

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You say you adjusted the rod length on the brake booster but I think I'd have another look at it. I've been using this cheap tool for proper adjustment and it makes setting the rod to the proper depth easy.


I have the same set up of non-ABS 80 series master and 80 series booster on my FJ60 along with 4 wheel discs (Tundra brakes front, 80 series rear) and this system works great.
 
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Hey All, success!!! :steer: 👍
Thanks so much for the help.

Sooo... It turns out with all the assist of the 80 Brake Booster, it will allow you put your foot to the floor, or close to it.

I carefully buttoned up everything this morning and took it for a cautious drive. The brakes work amazingly well. The wheels will be locked up at about 1/2 of the total stroke of the brake pedal. ...I can't even imagine the pressure of the system if I push it all the way to the floor.

I was also concerned they would be over-boosted, but that doesn't seem to be the case. It will take some getting used to, but they still have some good feel to them at lighter brake pressure. And yes, the proportioning valve was necessary.

Sorry if I jumped the gun with the original question. I was tired and frustrated, and just couldn't imagine the brakes were working correctly when the pedal would sink so far. Turns out offering up my problem to the Cruiser Universe, and a day off, were all it needed.

So,
-FJ80 non-ABS Master Cylinder
-FJ80 brake booster
-Tilton proportioning valve
-Wilwood front calipers and rotors
-Monte Carlo rear calipers

And they all play well together and provide excellent brakes.

Thanks again for the help ,
B.
 
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Joined
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You say you adjusted the rod length on the brake booster but I think I'd have another look at it. I've been using this cheap tool for proper adjustment and it makes setting the rod to the proper depth easy.


I have the same set up of non-ABS 80 series master and 80 series booster on my FJ60 along with 4 wheel discs (Tundra brakes front, 80 series rear) and this system works great.
Thanks Godwin! I got it working!
I very well may get back in there to readjust and that tool will be very helpful. Tough to do without it.
 

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