Dope

Hi guys,

This has been a problem for quite some time now and I haven't been able to figure it out.

First off, I bought my car 2 years ago. Brakes were fine then - pedal pressure was normal. It's a 99 FRC FYI.

I store my car in the winter since I live in MA. After the first winter storage (somewhere around 4 months), the brakes were mushy. Very soft for the first 1/2 of the pedal travel. Maybe a little less. It's soft until right about where the pedal is even with the gas pedal. Then it becomes hard again. Brakes still work fine, can engage ABS at will, just the pedal is soft and with my size 15 clompers, I hit the gas a lot when hitting the brake. That summer I bleed the brakes with a Mityvac vacuum bleeding setup. I run a full liter of ATE superblue through the system. No change.

Winter comes along again (this past winter), and I store it again for 4 months. Break it out, and the pedal is even softer now. It's literally feather soft for the first half of brake travel.

So this past weekend, I put some new pads on the front (figuring maybe a really low pad can cause a low pedal), along with new rotors and goodridge stainless lines all around. I also install speed bleeders all around. I bleed the brakes with the engine off, then with the engine on (going in the right order of course). Go through another full liter of ATE. Old fluid looks great. No bubbles, no discoloration.

No change in the pedal. Although now when it hits about halfway, the pedal gets REALLY hard (I attribute this to the stainless lines). The first half is just as soft as before though.

I have no leaks that I know of. I have checked all the fittings several times and have even switched to the AN Goodridge lines from Mallett to eliminate the banjo fittings. Fluid level in the reservoir does not drop at all. The pedal is ROCK hard with the engine off. Don't even really have to pump it up. It doesn't bleed off either, keeping pressure on the pedal doesn't budge it.
Again, car will still brake fine after I get past the 'soft' part. It's just getting bad enough that it's annoying to drive, and it's also kinda dangerous because I hit the gas and the brake together pretty much all the time.

So what I'm getting at is: what next? I've always heard that if the pedal is hard with the engine off, your master cyl is fine. And also, if the pedal doesn't bleed down with the engine off, then you don't have any leaks. So what does that leave? It seems like there's air in the lines but how? From where? I even went so far as to seal every fitting (in each wheel well) with teflon tape just in case. And again, doesn't appear to be leaking a drop. The braking system was also untouched before all this happened, as far as I know. Only after storing the car did the problem arise.

*scratching head*

I have had the drivetrain out a time or two, if it matters. Never touched the braking system but is there something I could have damaged? I know the brake lines run down the tunnel. If they were crushed or something, would that cause the problem?

Grrrr.

Dope

Dan_the_C5_Man

This isn't the first post I've seen on the CF of this nature.. And if memory serves it seems like the "solution" the stealers came up with was to replace the master cylinder..

I know you are a "do it yourself guy", as well as I.

The only thing I can think of is water / air trapped in the ABS / AH module (if your car has AH.. My FRC doesn't, thank goodness). And I've heard you need a Tech II to bleed the system properly (holding the internal valves open during the bleed that would otherwise be impossible).

But if you really think it thru, why would the pedal be solid after a certain portion of the stroke? Really does seem to point to the master cylinder; either that, or *something* is taking up slack (pistons retracting in the calipers more than "normal", brake pads cocked in the calipers, etc.)

Let us know what you find.

Dope

Hummm. Well it looks like I'll be trying the ABS thing first. It doesn't really make sense, but it's a lot cheaper and easier than replacing the master. After that I guess I'm truly out of options.

Dope

Dope

Oh, and I've heard of a DIY method of bleeding the ABS. Basically you have to drive around, engage the ABS a few times, drive back, leave the car running, and then bleed the brakes fully again.

I'm really leaning towards it being something else, because like I said, nothing was changed in the braking system to cause this, it just happens after storing the car. Maybe the master has a busted seal or something.

Dope

Bill Dearborn

Is the pedal really soft or do you just have excessive pedal travel before you get to the point where the pads engage the rotors? There is a difference between the two and the diagnosis depends on knowing which problem you have. With the year of the car the SS lines should not have provided a difference in brake feel. They do not provide much different brake feel than newer rubber lines.

On my 97 and on my 03Z the brake pedal (when everything is fine) will drop down about even with the gas pedal which makes it nice for heel toe action. As the pads get worn they tend to taper significantly and once you take your foot off the brake pedal for a while the pads/pistons will get knocked back. When you hit the pedal the next time the tapered pads have further to travel before touching the rotor and you get a long pedal. If the pedal is soft and you have to pump it to get it hard then you possibly have air in your lines. You could have a combination of the two problems also.

Bill


Not sure what the car running has to do with bleeding the brakes. Sounds like a myth to me.

Dope

Pedal is definitely soft. The brakes are working somewhat for the first 1/2 of pedal travel but not like you'd expect. Once the brake pedal is even with the gas pedal is about where the pedal gets harder and the brakes really start working.



I agree, but I'm saying that the car barely is stopping at all at that point (the 2 pedals being even). To get good braking performance you have to push the brake pedal beyond the gas pedal which is really bad with my giant feet.

Agreed, but I just replaced the pads and it didn't make a difference. The problem exists even if I'm not moving.

Pumping it with the engine running doesn't make it firm. It's the same every time I hit the pedal, no matter how fast and often I hit it.

I was pointed in the direction of a thread on the topic by a fellow on Z06vette.com, who appears to have had the same problem, and replaced everything to discover it was the brake booster. Hmmmm.

Dope

BQuicksilver

Check this out, it was what caused my car to act like you describe.

http://www.z06vette.com/forums/showthread.php?t=80525

Dan_the_C5_Man

Wow! I wonder how long it took that guy to figure that one out! Cool video.. Maybe you'll get lucky and find something similar?

yellow01

Dope,

I've had a similar issue lately - you can search the AC/RR forum and see it in excruciating detail. I'm going to try and bleed the master as well, but I've improved the situation somewhat through weeks of trying...I bled the calipers 'til I was blue in the face (actually until my wife's leg was sore) and this didn't help.

The other day at a track day I got into the ABS a few times (intentionally) and then bled again. Pedal did improve, but not to what I remember my '01 being.

The fact that it seems very soft for the first half and then "VERY HARD" in your words for the second half of travel leads me to think booster or the master though (I agree a with Dan above) - (my C5 doesn't do this although the pedal is softer than I like).

This page http://auto.howstuffworks.com/master-brake1.htm has two great animations that show the master at work (simple stuff but was helpful to me for picturing it in my mind). Check out the one with a leak - an internal leak past a piston seal in the master can have the same effect, causing the first portion of the stroke to be soft, but...if you put your foot on it and keep pressure on the pedal does it slowly sink?

A replacement master is actually relatively cheap ($157+ship) from Fred Beans. I know this is no drop in the bucket, but it isn't monumental either. Not sure what the labor would be.

Dope

Jesus, I never would have thought of that. I'll have to take a look when I get home from work.

Dope

99Red&White

Check your brake booster hose. I know when cars get older, they actually collapse under the vacuum and cause that spongy brake pedal feeling. I doubt this is your problem though..

Dope

Interesting diagram in those links. I guess it makes sense in theory that it could have a leak and cause this effect. The reason why I was doubting this in the first place is because I've been checking my fluid level for literally a year and it's been fine, hasn't budged a bit.

Just to clarify, when I say the pedal is soft and then really hard, I was trying to illustrate that the stainless line install did have an affect - but only on the 2nd half of the brake travel. Prior to the stainless lines, the pedal was soft for half, and then normal for the 2nd half. After stainless, it's soft fo rhalf, and hard for the 2nd half. Make sense? The lines didn't affect the 'problem' but did affect the 'normal' part of brake travel.

Regarding the pedal slowly sinking under pressure - do you mean with the car on or off? I'll have to try it when I get home. I'm pretty sure it doesn't sink with the car off, but it does with the car on (at least, until it hits that half-way point).

Dope

yellow01

Dope,

I posted the pic because the link could be INTERNAL. If one of the piston seals in the master is failing, the fluid on the pressure side can leak to the other side of the piston (kind of like a blow-by). No external fluid loss would be noted.

if this happens the pedal will typically slowly sink with constant pressure. It should happen with engine on or off; however, if the leak is small without the boost there may not be enough pressure to make a difference.

Don't confuse the softness with a sink...push the pedal down until you feel good resistance, then continue to apply pressure and wait...if the pedal slowly sinks lower and lower to maintain the same pressure you may have an internal leak in the master.

Hope this helps

Dope

Weird I could've sworn I replied again.

Anyway, I get what you're saying. I'll try it tonight.

Thanks,
Dope

Dope

Small update.

Checked that big vacuum hose into the booster. It's fine.

Checked the pedal 'sinking'. It does sink, engine on or off, but only for that first half of the pedal travel again. Once it hits that 'normal' range (about even with the gas pedal) it stops sinking.

Something interesting to add, the car has a line lock (from several years ago). It's a Hurst Roll Control, which is plumbed directly into the lines coming out of the master. I wonder if that could affect things.

At this point everything seems to point to the master. Think I might try 'bleeding' the lines leading out of the master as described earlier. Just for curiosity sake. But with the 'sinking' with the pedal on and off, I think it's leaning towards the master. Plus, I would think a brake booster problem would cause a soft pedal the entire length of the pedal travel, OR a hard pedal the entire length if it wasn't boosting enough. Just halfway makes no sense. The design of the brake booster tells me it should either work or not, none of this halfway crap.

I'll update in a week or so when I swap it out.

Dope

yellow01

Dope thanks. PLEASE PLEASE PLEASE post an update or IM me with one.

I'm fighting the exact same thing and just can't seem to remedy it. (I'll do something, think it's better and then fool myself with wishful thinking ). I bled lines out of the master yesterday to no avail, and I checked the vacuum lines a while ago.

I've been leaning toward the master due to the two piston thing/halfway thing (mine gets strong around the same point - the brake pedal) and leaning toward just replacing it, unfortunately, I have a track weekend this weekend...not much time. Since I can still lock 'em up I'm going...just makes downshifting a bit harder.

Do you know which line out of the master is for the front & rear brakes? The forwardmost & rearmost line out of the master? If there's an internal leak one should be less effective and generating less pressure...

Good luck and please do post an update.

Dope

I believe it is the rearmost line on the master. This is the one that is tapped into for my line lock (which locks the front wheels) so it makes sense.

I'm ordering a master today, hopefully get it installed the weekend after this one (I doubt I'll get it in time for this weekend).

Dope

Umrswimr

I'm having the same issue. I made the mistake of using a vacuum bleeder on the caliper side. Pedal feel is similar to described.

How do you bleed the master?

yellow01

the GM sheet that Patches sent me says

then goes into standard pedal bleed procedure. So this assumes the master has already been bench bled. Since our masters are already on the car, I think it's a fair assumption unless the resevoir has been run dry (and I doubt that has occured).

Dope

Don't think there's anything wrong with a vacuum bleed, I've done it before too. Lots of guys do it. I have the Mityvac brake bleeding kit.

Dope