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Old 04-03-2016, 10:00 PM   #1
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hakachukai is on a distinguished road
Join Date: Apr 2016
Posts: 16
Dazed 97 SC2 (No ABS) Brake Pedal goes to the floor

I have a very strange issue that I can NOT figure out!

I have a 97 Saturn SC2. About 1 month ago the car was driven about 10 miles with the E-brake left on a few clicks. The car then experienced total brake failure and had a light 15mph crash into the bushes.

The car didn't have anything but slight cosmetic damage.

So I replaced the rear brake shoes ( both sides ) because they were heat cracked.

I replaced the Passenger Rear wheel cylinder and brake hose because it was sucking in air.

However the brakes still didn't work properly. Anytime that car is running the brake pedal goes to the floor ( although the brakes do work well enough to lock up the wheels at 60mph ).

I found that if I squeeze both front brake hoses shut [ at the bottom of the hose ] ( both at the same time ) the pedal becomes rock hard ( with the car running ).

So I replaced both front calipers and pads. No good! The problem remains :-(

So I replaced the master cylinder. No good! The problem remains :-(

I've bench bled the master cylinder 3 times in a row. There is no air in it.

I've bled the system at all 4 wheels at least 5 times now. There is no air in it.

I've bled the lines at the master cylinder about 5 times now. There is no air in them either.

I also adjusted the rear drum brakes so that they are as tight as they can be without dragging too much.

The rotors are not warped at all. The brakes are smooth as butter.

At this point I've replaced everything in the brake system except:

The drivers side rear wheel cylinder ( which is not leaking )
The brake hoses and lines ( which are not leaking or swelling ).

The exact symptoms are:

1. With the engine running, the pedal goes almost to the floor every time with a single hiss. The brakes do work and are able to lock up the wheels no problem, but the pedal travel is WAY too much!

2. Immediately after shutting off the engine, the brake pedal still goes to the floor. After I pump the pedal 3 or 4 times ( with the engine still off ), it's rock solid again. I think this is because it lets the vacuum out of the booster.

3. With the engine off, the brake pedal is rock solid! I even did a test drive with the vacuum line to the vacuum booster unplugged. With the vacuum booster disabled, the pedal was rock solid the entire time and I was almost able to lock up the wheels ( though I wasn't quite strong enough ). The car had no problem stopping quickly from 60mph, but it was very hard to push the pedal.

4. With the engine running ( normal conditions ), I notice that when the brakes are pressed the back wall of the vacuum booster presses outward toward the front of the car. It also moves the master cylinder with it and flexes the brake lines a tiny little bit. I don't know if this is normal or not.

How is this possible?!?!

Is something physically wrong with the vacuum booster that some how makes it fail if it is used? I'm completely stumped on this one!

How can the brakes work perfectly when the vacuum boosted is disabled, but have a mega-ton of pedal travel when the vacuum booster is used?


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