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Old 04-03-2016, 10:00 PM   #1
hakachukai
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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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Old 04-03-2016, 11:15 PM   #2
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Default Re: 97 SC2 (No ABS) Brake Pedal goes to the floor

I wasn't able to find a way to edit my previous post, so I'll add something that I forgot to list here:

After the brake failure / accident I also tested the old brake fluid for boiling point. The boiling point was between 400 and 450 DegF. Nothing unusual there.

Afterward, I drained the entire brake system and replaced the brake fluid anyway ( just for the sake of cleanliness and completeness ).

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Old 04-04-2016, 03:08 AM   #3
el diablo viejo
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Default Re: 97 SC2 (No ABS) Brake Pedal goes to the floor

I have a similar problem on my SW1. Strongly suspect the master or the vacuum boost, but I have not dug into it yet. Very interested to hear what the solution may be.

...
97 sl2 a/t 104 K
1989 GMC 3500 454 129 K, 1969 442 455 rat rod

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Old 04-04-2016, 01:23 PM   #4
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Default Re: 97 SC2 (No ABS) Brake Pedal goes to the floor

When you drove the car with the parking brake applied, the rear brakes dragging and causing brake damage also cooked brake fluid. The overheated brake fluid expands and either expands to return fluid back into the master cylinder or has no place to go when brakes are applied (master cylinder ports are closed off to allow building up hydraulic pressure when stopping with the vacuum brake boost multiplying braking forces). Heated enough, brake fluid will boil and may create air as DOT-3 brake fluid easily absorbs moisture. Once this occurs, its wise to simply flush all brake fluid and replace it - a full system flush and bleed. Somewhere during this overheating phase, it may have damaged the master cylinder seals or at least the rear wheel cylinder seals, being closest to overheating brake shoes. Replacing both front calipers and one rear wheel cylinder leaves one more wheel cylinder in question. Remember, anytime brake fluid overheats, in this case with Parking brake applied for 10 miles, may cause more damage than can be seen. Since brake fluid doesn't let anyone know when it overheats, hot oil can cook rubber seals hidden from view. Replacing both wheel cylinders is just another procedure to eliminate problems. Brake oil seeping out the rubber seals on wheel cylinders is a tell tale sign of damage.

While your situation is completely different from another member here, its worth mentioning as a precaution and heads up warning. A member inadvertently put the wrong caliper on his front end resulting in air remaining in the caliper and unable to bleed it. It was determined he put this caliper upside down with the bleed screw towards the ground, effectively never allowing air to leave since air simply floats up, away from the incorrectly installed caliper. This new member didn't realize calipers are made for right and left side and simply ordered the wrong caliper. Even his close up picture was overlooked by everyone. A trip to a brake shop and about an hour of several brake techs butting heads determined the wrong caliper was installed with the bleed screw pointing down instead of up. Once this was clear, this member realized his mistake and hasn't replied........... Simple error but eluded everyone here.

The last wheel cylinder not replaced and a full system flush of all old brake fluid may correct this issue. NEVER use the engine for brake bleeding or flushing procedures. The brake vacuum boost unit multiplies brake pedal effort and can cause injury to anyone not aware of higher hydraulic pressures if a bleed screw is opened. Think high pressure when vacuum boost is used. Brake hydraulics are always flushed/bled with the engine OFF. You're probably not aware that all car brakes are dual diagonal systems - the right front and left rear are on one line of the two lines leaving the master, the left front and right rear are on the second line from the master. Master cylinders have two pistons, each one serving half the brakes. Dual diagonal brake lines are designed so in the rare case one line is damaged, only one half the brakes are lost. The remaining half can still slow a car down while not throwing the car sideways as the diagonal brakes prevents brakes from pulling a car to one side.

By creating an unusual situation, careful assessment of the entire brake system is needed to fully appreciate what occurred and what's necessary to restore full braking function back to normal. This may be one of a few exceptions where everything must be considered and replaced to remove and eliminate a sinking brake pedal.

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Old 04-04-2016, 03:08 PM   #5
GuiltyByDesign
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Default Re: 97 SC2 (No ABS) Brake Pedal goes to the floor

i had the same problem with a prelude, and i replaced everything but the break lines. i even purchased a vacuum bleeder but that didn't help either. i believe what the system needs is a pressure bleed to force a large quantity of fluid, along with the air, out of the system.

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Old 04-04-2016, 03:23 PM   #6
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Default Re: 97 SC2 (No ABS) Brake Pedal goes to the floor

This is the bit that concerns me the most.....

"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."

Brakes are the difference between you and a hospital bed, so IMHO never take chances with brakes. If you are unsure, get an expert to look at it.

It could be worth while just calling in to somewhere like "Just Brakes" and have them check it. They will obviously want to do the job on your car if they find anything, but that's your choice. Better to be safe than sorry.

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Old 04-04-2016, 07:34 PM   #7
hakachukai
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Default Re: 97 SC2 (No ABS) Brake Pedal goes to the floor

After further investigation I now believe that the problem might be caused by physical issues with both front calipers.

Here are 4 videos that I took of how the calipers move when I used the brakes ( boosted and un-boosted ). In this video the disc is tightened down using the lug nuts.

It looks to me like they have too much movement and also the piston is sliding sideways a bit. I'm not sure why this is happening yet, but the car does easily pass a shake down test. There is no obvious problem with the wheel bearing.

Also, the way that the pedal feels lines up with how you see the caliper move.

At first the pedal feels like nothing at all ( this is when the caliper piston is taking up the empty space ).

Next it firms up, but still feels spongy. This is when the brake parts are flexing.

These videos are on youtube. This site won't let me post links because I am too new, so you can just copy / paste the lines below at the end of the you tube url and it'll work.

Front left caliper and piston:
watch?v=ssvfzI3vZIE
watch?v=lEJNOeSDR4M

Front right Caliper and piston:
watch?v=b9LK5YwwmVQ
watch?v=-0BFDNl3Z8M

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Old 04-04-2016, 09:51 PM   #8
GuiltyByDesign
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Default Re: 97 SC2 (No ABS) Brake Pedal goes to the floor

they look fine to me. i think the air in the lines is exaggerating the feel of engagement to the break peddle. as i stated before you should take it to a shop and have it pressure bleed

here is an image of caliper function to compare

weblumen.com/images/tools/brakes/Brake-Ani-sml.gif

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