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Discussion Starter #1
Ok, it's a 94 TT 6 speed. Trac eliminate was done, other than that the entire system is stock (lines, calipers)

Problem is the brake pedal feels normal on initial hit, but fades about 1/2 way down then stops and is as firm as it's supposed to be. On first thought, it's air in the lines, so bleed them....right! No change at all. Fluid is max. I can almost feel the back brakes fade away when the pedal fades. When the pedal stops 1/2 way down the fronts are 100%, rears are basically 0%.

I've bled plenty of brakes but these are not right. Just tried to bleed them again, and there is no pressure going to the back brakes!?! Car off, pump pedal and it does not feel right. Pressing on pedal hard, open rear bleeder, and nothing...just dribbles out. Fronts bleed as should. You can tell by the wear on the rear rotors that the back brakes have not been working correctly for some time.

Master cylinder?
Something to do with the Trac removal? (although I've done this to 3 other cars with no issues)
Brake booster?
Crushed rubber line?

Any help or advice is appreciated.

Thanks,
Alex W.
 

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Discussion Starter #3
That would explain the imbalance, but not the fading. Plus I don't think I've ever ran into a bad Proportioning valve.

Alex
 

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Although this is not the same car, my brother's ford ranger had the same symptoms. His front brakes wore out in less than 2 yrs so I replaced them. The brakes had good feedback but you would have to put in a little bit more force to come to a complete stop. When I bled the brakes, the rears did not let out any fluid. I took off the line leading to the drum and nothing came out. I went to the MC and fluid came out. I then went down the line and found the ABS modulator. This was basically a brass block with two electronic solenoid valves on it. The solenoid valves stop the flow to the rear brakes when the ABS is actuated. I disconnected the line out to it and nothing came out when the brake was pushed. When I removed the inlet line and pushed the pedal, fluid came out. So I ordered a new ABS modulator and will install it this week.

I am not that familiar with the braking system of the supra but I believe that the NA has a 3 channel ABS system while the TT has a 4 channel. The 3 channel actuates both rear brakes at the same time like the ford truck.

However, since you have a 4-channel system it is probably your proportioning valve. Otherwise, it could be your ABS modulator. Good luck
 

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OVRBST said:
Ok, it's a 94 TT 6 speed. Trac eliminate was done, other than that the entire system is stock (lines, calipers)

Problem is the brake pedal feels normal on initial hit, but fades about 1/2 way down then stops and is as firm as it's supposed to be. On first thought, it's air in the lines, so bleed them....right! No change at all. Fluid is max. I can almost feel the back brakes fade away when the pedal fades. When the pedal stops 1/2 way down the fronts are 100%, rears are basically 0%.

I've bled plenty of brakes but these are not right. Just tried to bleed them again, and there is no pressure going to the back brakes!?! Car off, pump pedal and it does not feel right. Pressing on pedal hard, open rear bleeder, and nothing...just dribbles out. Fronts bleed as should. You can tell by the wear on the rear rotors that the back brakes have not been working correctly for some time.

Master cylinder?
Something to do with the Trac removal? (although I've done this to 3 other cars with no issues)
Brake booster?
Crushed rubber line?

Any help or advice is appreciated.

Thanks,
Alex W.
Alex,

how did you bleed them and have you always had the problem or is this recent?

I'd get them bled with a vacula to pull fluid thru the whole line...... if you have air stuck somewhere it will get it. Sounds like you have some air in the system.

FWIW, Sears at the Mall of NH did my 95 - changed all the brake fluid with a vacula for $60.

sent you email on sidebar stuff.

-M
 

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Discussion Starter #6
That ABS info is good. I'll check that out for sure. I'm very sceptical about the proportioning valve only because I've never had one go bad. I'm hoping it's nothing to do with the ABS modulator (expense reasons mainly).

I bled these the same as all others I've done. I'll go borrow my friends vacula and try again, although I feel the main purpose for that tool is single man brake bleeding. If the force of a person pressing on the brake pedal forces no fluid out, then I'm sure a hand pump cannot draw fluid. Either way I'll try it and see. I'm going to disect some more things in the mean time.

Its been a problem for a while, just never bothered me enough until now.


Alex
 

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pedal pressure draws fluid out but it doesn't pass much fluid thru the line. If you have a bubble in the line, you need to flow it all the way thru.... sometimes you get a "sticker" and pulling it thru with a vacula can flow enough without the back and forth of the pedal. I don't think there is a blockage, that's not what I meant.

You have access to a vacula? hmmmm....... you know what I'm thinking.

-M
 

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If you end up needing a new ABS unit let me know. I got a perfect one sitting here collecting dust !
 

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Discussion Starter #9
If you end up needing a new ABS unit let me know. I got a perfect one sitting here collecting dust !

SWEEEEEEET!

Well, times up anyway. I have to go back to work and I'll be out flying around for the next 6 days. I got my hands on a sick power bleeder that BMW uses. It's a big closed loop system with some weird bleeder screws that need to be special ordered and it uses blue brake fluid. That will surely solve any and all bleeding issues that I may or may not have. Then we'll see after that.

Later,
Alex W.
 

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OG
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im pretty sure its your master cylinder.

basically, it sounds like you got air into the master cylinder itself.

there is a different procedure to bleed the master. you need to disconnect both lines going into it. then push the pedal and let the fluid squirt out. leave a towel there to absorb the fluid. then have someone plug the 2 openings with their fingers, then release the pedal. do that a few times and you'll get the master bled. you'll notice the fluid kinda dribble at first, but by the third attempt, you should have full pressure and the fluid should shoot out like a squirt gun.

hope that helps.
 

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Discussion Starter #12
Al, I think you are correct. The symptoms seem to lead me to the master. I "think" the power bleeder will bleed the master as well. If not please tell me, that way I can bleed the master first. I'm looking forward to having some nice tight brakes again....in all 4 corners. Either way I will let you know how it works out. I won't be home until Tuesday Evening so I have to wait :(.

Mark, the power bleeder belongs to Tulley BMW in Nashua. A close friend works there and it took some convincing to let me borrow/use it. Not to mention he's going to be there when I do it. I don't think he wants to go to Manch. I'll ask and see. He has to order the special fluid and bleeders for my car, so if he says yes it's about $45 for all the stuff you need.


Alex W.
 

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I'd like mine bled, see if he's up for it.

thanks
 

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I wouldnt think it was the master cylinder. Everytime I see a master cylinder go bad or draw air in it, it effects the front and rear brakes the same and you will not have a pedal. Maybe it is...regardless I dont have any better recommendations because Ive never seen anything like that before. I would just shy away from the master cylinder is all im trying to say.
 
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