Mechanics

BRAKE PEDAL GOES TO THE FLOOR WITH NO PRESSURE

1990 Oldsmobile 98

Brake pedal is loose and goes all the way to the floor. It will stop the car for a second but then nothing and keeps rolling. It is also slow to come back up to normal position. I replaced the master cylinder gasket since that was all wrinkled up so it wouldnt build pressure. Still the same problem though. Any ideas on how to get the brakes to work? Is there any special way to bleed the brake lines? Need help asap.
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Koenck26
May 31, 2013.




You have a leak in the hydraulic system. If the level is going down in the reservoir you have an external leak. Look for a puddle under the car or wetness on the inside of one of the tires. If the level is not going down you have an internal leak in the master cylinder and it will need to be replaced. Even if you find an external leak you can expect the master cylinder to be damaged from pushing it all the way to the floor. The lip seals get torn on the crud and corrosion that build up over time in the areas the pistons don't normally travel in. Not sure what gasket you're referring to. There's no external gasket that will prevent pressure from building in the system.
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Caradiodoc
May 31, 2013.
No puddles or wet insides of tire. Gasket is on inside of master cylinder top cap. You think replacing the master cylinder would fix it?

Tiny
Koenck26
May 31, 2013.
Yup. If you're not losing any brake fluid from the reservoir, the lip seals inside the master cylinder are torn and leaking. You have to be careful with the new master cylinder on GM cars. Never push the brake pedal more than half way to the floor. Doing that will trip an internal valve and cause one front brake and the opposite rear one to not work and you won't be able to bleed any fluid and air out. You likely won't even notice the loss of braking ability but only two of the four brakes will be working.

Caradiodoc
Jun 1, 2013.

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