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hakachukai 04-03-2016 11:00 PM

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?

hakachukai 04-04-2016 12:15 AM

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 ).

el diablo viejo 04-04-2016 04:08 AM

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.

fdryer 04-04-2016 02:23 PM

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.

GuiltyByDesign 04-04-2016 04:08 PM

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.

floridasl22002 04-04-2016 04:23 PM

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.

hakachukai 04-04-2016 08:34 PM

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:

Front right Caliper and piston:

GuiltyByDesign 04-04-2016 10:51 PM

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

fdryer 04-05-2016 04:35 AM

Re: 97 SC2 (No ABS) Brake Pedal goes to the floor
Front left caliper; [url][/url]

Front right caliper; [url][/url]

While it was nice of you (or anyone) to video capture applying brakes with and without the engine running (without wheels mounted and rotors locked in place with lug nuts), the video may be giving false impressions.

The main caliper assembly is designed to "float" over two caliper pins mounted with plenty of clearance inside two rubber boots holding high temperature grease. The caliper is allowed to freely align itself over these two pins while straddling the rotor disc. The disc is relied on being bolted in place to the wheel hub to have less than two thousandths of an inch (0.002") lateral runout (disc warp) with the wheel bearing not having any slop. The disc is presumed in most cases to run true. The caliper is allowed to float sideways to automatically align itself to the rotor disc. As soon as braking is applied, the piston on one side of the caliper is pushed out against that side of the brake pad while the caliper moves sideways until the other brake pad contacts the other side of the rotor disc. At this moment the caliper is aligned and acts as a fat 'C' clamp to compress brake pads against the rotor. The self aligning caliper depends on the greased pins to provide self alignment at all times. In reality, once brakes are serviced with new pads or rotors, the piston is retracted with a lot of space between brake pads and rotor disc. This large air gap is gone as soon as brake pedal is applied; brake hydraulics forces brake fluid into the caliper to push the piston out. As soon as the first brake pedal is applied, all the slop is removed with the caliper aligning itself to distribute pressure to both brake pads. When braking is released, the caliper piston and very imperceptible rotor runout forces the piston back into its caliper housing - just a few thousandths of an inch and not visibly noticeable but enough to see the brake pads still slightly rubbing against the rotor faces. This is acceptable and not considered drag or pad/rotor overheating. The caliper is effectively aligned for the life of these parts and continually moves very slightly as brake pads and rotor wear down. When new parts are used and the caliper piston is fully retracted into home position, you can move the caliper sideways and twist it in place to see how much slop the caliper pins allows for freedom of movement. As long as the pins and grease allows free movement, the caliper will self align automatically to allow pads to wear down evenly.The video is showing a false impression as if the rotor is moving sideways against the fixed caliper. Are you sure the rotor is bolted and not free to move sideways?

Do not assume what you see is correct as its shown with the caliper not moving and appears as if the rotor is being moved sideways. Unless you mount the wheel back in place or ensure the lug nuts are bolted to hold the rotor in place against sideways movement, you're being distracted with misrepresentation of a nice video. Remember this, the rotor disc is fixed against sideways movement when a wheel is bolted on. The caliper is always floating across the two "slide" pins to allow it to self align. Try imagining a fat "C" clamp with two holes for pins, one at the top and the other on the bottom. The holes for the pins have a rubber boot to hold grease and large enough to have a sloppy fit so the "C" clamp can move axially and perpendicular - all to allow as much freedom to move sideways on these two pins. The pins are bolted to the (separate) caliper frame. When brakes are applied the caliper slides slightly, the piston moves out and presses against the brake pad that presses against the rotor that presses the opposite pad resting against the caliper body. This large "C" clamp simply floats into position to clamp both brake pads against the rotor disc to slow it down from turning.

hakachukai 04-06-2016 12:35 AM

Re: 97 SC2 (No ABS) Brake Pedal goes to the floor

I understand what you are saying. The rotors were bolted down during that test. However I didn't use any specific torque. I just put them good and tight.

I'll try the test again with the wheel mounted and properly torqued, but the issue with that is that it's nearly impossible to even see the caliper or rotor with the wheel mounted.

I have obtained a pressure bleeder, so the first thing that I'm going to try is pressure bleeding it to see if there is trapped air in the system anywhere.

hakachukai 04-06-2016 03:29 AM

Re: 97 SC2 (No ABS) Brake Pedal goes to the floor
I just got done pressure bleeding all 4 wheels.

I did the pressure bleed at 18psi

I opened up the bleeder 1 to 1.5 turns to allow max fluid flow ( because I'm trying to get air bubbles out of hidden areas of the system ).

I pressure bled 295mL of brand new, perfect, clean looking DOT4 fluid from all four wheels. Not a single air bubble in sight :-(

Re-installed / torqued the wheels to 103 ft-lbs

No change :-(

The pedal still goes nearly to the floor ( exactly like before ).

hakachukai 04-06-2016 07:24 AM

Re: 97 SC2 (No ABS) Brake Pedal goes to the floor
Minor update:

I didn't notice at first but the pedal is now a good bit stiffer after the pressure bleeding. The pedal still will go to the floor, but it take more effort to make it do so.

I don't know why though, because when I did the pressure bleeding I didn't see anything come out that was bigger than the sharp point on a needle.

underthehood 04-06-2016 07:29 AM

Re: 97 SC2 (No ABS) Brake Pedal goes to the floor
Why are you using DOT4? DOT3 is what is recommended IIRC. That being said have you replaced the other wheel cylinder? I may have missed it but did you replace all brake hoses and calipers? What order are you doing the bleed in? Are you using a small hammer to tap the calipers and cylinders while doing the bleed (yes air can and will "hide"). What condition is the master in? BTW re having to put the wheels on or "torque" the lugs. Not necessary. Just put the rotors on and "snug" the lugs. It's all you need. Did you grind the "ridge" down on the rear drums BTW? If not, do so. Than readjust the rear brakes and see where you are.

Steve44 04-06-2016 01:07 PM

Re: 97 SC2 (No ABS) Brake Pedal goes to the floor
Although I don't ever recommend pressure bleeders, I'm going to assume that you have indeed bled all air from the system. Based on that assumption, here's what you need to do. Pull up your parking brake lever.
Count the number of "clicks"
If You have more than 5 clicks, your rear shoes are out of adjustment.
Proper adjustment of the rear shoes (assuming you've installed them correctly)
depends of the drum being free of any rusty outer lip.
If there is this lip, take some 40 grit sandpaper (Or whichever method the next 4 people will suggest) to clean the surface.
Now you can adjust the shoes, then put the drum back on.
Adjust until you have a slight drag, not hard to turn.
Hope that helps. :)

fdryer 04-06-2016 01:20 PM

Re: 97 SC2 (No ABS) Brake Pedal goes to the floor
Instead of four people with each one having a suggestion, how about one people with four suggestions? 1)Hand filing (most difficult and very time consuming), 2)dremel tool with a grinding wheel (a little less time consuming but still labor intensive), 3)portable hand grinder for much less time spent and lastly, 4)taking drums to a brake shop for them to machine drums. They can take off the lip or resurface the drum to like new condition if you're willing to pay the fees.

floridasl22002 04-06-2016 01:29 PM

Re: 97 SC2 (No ABS) Brake Pedal goes to the floor
I will repeat this as no-one seemed to pick up on it last time...

The OP said that when he put his foot on the brake with the engine running, the vacuum servo was physically moving along with the MC from the firewall. That cannot be right?? That coupled with very little pressure at the pedal leads me to think that the problem is not at the caliper end or ridges on the rear drum, but at the MC/Vacuum Servo.

Meanwhile the OP appears to be still driving this car, which has a braking deficiency!!!!

Rather than playing guessing games here, my suggestion would be have a professional check it out, before someone gets hurt.

hakachukai 04-06-2016 06:37 PM

Re: 97 SC2 (No ABS) Brake Pedal goes to the floor
After taking the car in to be checked out by an ASE certified mechanic I found the following:

There is nothing wrong with the braking system.

The pedal is not as hard as the pedal that I'm used to in my honda, but the mechanic told me that it is well within acceptable range. During driving the brakes also have no problem stopping. I'm only having to use 50% of the pedal travel to stop ( even for quick stops ). If I used the rest it would lock the wheels up no problem!

The vacuum bleeding is what made the difference between the pedal being too soft to be safe and being ok ( but not real awesome in my opinion ).

So here is the actual solution:
Pressure bleeding the system at 18psi and draining 300mL of fluid from each wheel. Open the bleeders all the way so that fluid can flow as quickly as possible. If the fluid is flowing fast enough that it can force the air bubbles straight down in your drain bottle tube ( if your drain tube is larger than your brake lines ), then it will also be fast enough to get trapped air out of a downward facing line.

Here is a whole list of stuff that made no difference at all:
Replacing the rear wheel cylinder / brake hose
Replacing both front calipers and pads
Replacing the Master cylinder
Replacing the rear brake shoes
Properly adjusting the rear brake shoes
Bench bleeding the Master cylinder
Bleeding the lines at the Master cylinder
Vacuum bleeding all 4 wheels
Pedal bleeding all 4 wheels
Gravity bleeding all 4 wheels

I'll check out that moving vacuum booster / master cylinder soon and let you know what happens.

fdryer 04-06-2016 09:12 PM

Re: 97 SC2 (No ABS) Brake Pedal goes to the floor
Now that you found having to press the brake pedal hard enough to lock up brakes doesn't depend on forcing the pedal to the floor, the engine running and vacuum brake boost unit provides power assisted braking, the pedal doesn't need to travel to the floor.

You might consider the type of brakes plays a large role in effective braking. Rather than open up a debate on brake material advantages and disadvantages, everyone has their personal opinions about brakes whether racing, auto crossing or stoplight racing with soccer moms. Materials can be either ceramic or semi metallic with variations from one brand to another to allow a smorgasbord of braking efficiency (where debates occur). Personally, a rotor disc is a rotor disc - plain ones. Holes and slots are less important for the grocery getter/stoplight racers and more likely for visual appeal. Since they're proven in race tracks, I doubt anyone is driving with glowing red rotors in stoplight racing to have any real advantage in everyday driving. Unfortunately, drivers assuming their brakes and driving superiority coupled with abs will rule the road often find themselves in expensive accidents to prove driving simply requires a defensive awareness of other drivers while anticipating impending doom. Of course I can be absolutely wrong against soccer moms racing for the parking spot, with or without kids in the suv/minivan.................

GuiltyByDesign 04-07-2016 04:16 PM

Re: 97 SC2 (No ABS) Brake Pedal goes to the floor
[QUOTE=hakachukai;2186827]Minor update:

I didn't notice at first but the pedal is now a good bit stiffer after the pressure bleeding. The pedal still will go to the floor, but it take more effort to make it do so.[/QUOTE]

im glad that worked out for you i know first hand how infuriating and expensive brake problems can be

floridasl22002 04-07-2016 05:56 PM

Re: 97 SC2 (No ABS) Brake Pedal goes to the floor
I think this thread also highlights that sometimes going to see the professional in the first place CAN save money and avoid throwing parts against imaginary issues can be the best route.

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