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brake problem 88 900s

We bled all four discs diagonally. we rebuilt the master cylinder, then we bench bled it before we installed it back into the car. we cleaned all the calipers after we installed all new rotors and pads.

The problem is when I am driving the car and I apply the brakes I have a full pedal but as I am stopped the pedal begins to sink to the floor and the car starts to move and I then have to pump the brakes to keep the car from moving. (When the car is turned off the brake pedal is full and solid with no movement.

Any suggestions as to why the brakes won't hold?

Reply to
nikate
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You have brake fluid leaking past a seal in the system. If it was spongy at first, that'd be air; sounds like you got that all out.

Are you losing fliud anywhere? Check all 4 corners. If not there, then I'd suspect (strongly) the master cylinder.

The only difference between "on" and "off" is that there's vacuum at the power brakes servo, but I'm at a loss to explain why it would change your leak. Anyone?

I've got 50 (checks headers) dollars on it being your master cylinder. Any takers?

Dave Hinz

Reply to
davehinz

Seconded (word for word).

I've seen similar things with a 900 clutch - fine when car is standing, but when you drive, the master starts to let go. Heat.

10-20C can make a difference when the seal is marginal.

Unless you're loosing fluid, it's the master, no doubt about it. Where did you get your seal kit from? Are you sure it was the right one, not one where the seals were 'about the right size'? Are you sure you put all the seals and washers in the right order?

Reply to
Grunff

Good point; I've got a tractor (backhoe/loader) with a tranny seal that's just fine for a while, but gets drippy when it's warm.

On a side note, does anyone have experience with "seal conditioners", basically stop-leak for tranny seals?

Dave Hinz

Reply to
davehinz

Worth a shot, then. Thanks.

Dave

Reply to
davehinz

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