Very Weak and squishy brakes
Thread Starter
Intermediate
Joined: Mar 2002
Posts: 40
Likes: 0
From: Titusville FL
Very Weak and squishy brakes
I've been having this problem for about 3 months now...but now it's getting really bad. My brakes are pretty bad as they are, and they are constanly being worked on. Every time we get them worked on (at the chevy dealership), they work great for about 3 days, and then get very squishy and nearly go to the floor. One time the completly quit, and I had to get it towed. They replaced the front right caliper, and they worked great again for about 3 days.
Now, when I'm at a stoplight, and the engine is about to die (it runs very rich, another thing I'm working on), I push the brake with left foot, and barely tap the gas. When I do this, the brake nearly drops straight to the floor!!??
It's really strange, and when I want to stop, they hardly work after doing this! I usually just pull off the road using the e-brake, put it in park, and pump them a lot to get some pressure built back up, but when I put it back into drive, the brake pedal drops again, but not as far. It's just really weird, and no one seems to know what's wrong with it. Does anyone have any ideas? Thanks!
Now, when I'm at a stoplight, and the engine is about to die (it runs very rich, another thing I'm working on), I push the brake with left foot, and barely tap the gas. When I do this, the brake nearly drops straight to the floor!!??
It's really strange, and when I want to stop, they hardly work after doing this! I usually just pull off the road using the e-brake, put it in park, and pump them a lot to get some pressure built back up, but when I put it back into drive, the brake pedal drops again, but not as far. It's just really weird, and no one seems to know what's wrong with it. Does anyone have any ideas? Thanks!
Racer
Joined: Feb 2002
Posts: 276
Likes: 1
From: Arlington Texas
Re: Very Weak and squishy brakes (lanceh007)
Sounds like air is entering the system. Thye question is how and where? Do any of the calipers apear to be leaking? Has the master cylinder been replaced? I first thought the dealer is not bleeding the properly, but I don't think they would work for three days if that were the case. Also, check the p. valve and all fittings.
Thread Starter
Intermediate
Joined: Mar 2002
Posts: 40
Likes: 0
From: Titusville FL
Re: Very Weak and squishy brakes (Kingt)
well, that could very well be the problem. I don't know much about brakes at all, so I'd have to tell my dad what you guys are saying to check. I do know that there is a newer master cylinder (probably 4 months old). It was installed by the dealership. My dad had installed one about a week before the newer one I just mentioned, but it had somehow broken, so we took it to the dealer for them to put a new one on correctly. Also, I don't think the calipers are leaking. It stays in the garrage, and there is no brake fluid on the ground, so that's the only way I would know of them leaking. What else might it be?
Racer
Joined: Oct 1999
Posts: 353
Likes: 0
From: Cortland, NY, USA
Re: Very Weak and squishy brakes (lanceh007)
Corvette brakes can be a challenge, to say the least.
First - when they replaced the master cylinder, did they correctly bench bleed it? If not there is your answer.
Next, check all of your brake lines for possible leaks. Get some brakeclean and spray off any crud and check for possible pin holes, etc.
Usually, the problem you describe is due to what is called rotor run out. What that means is that the the brake rotors aren't truly perpendicular to the hub. This causes a small "wobble" which pumps the spring loaded calipers back and forth and actually pumps air into the calipers. The solution is to have a shop true up the rotors with a dial indicator to within .003 of true. Some people have had the rotors turned while on the car, but I can't speak for that. Believe me, it's for real and if you don't fix it you will lose your mind. Some high quality replacement calipers have double seals on the pistons to help prevent air entering as well.
Also remember there is an order to bleed the brakes and that the rear brakes have two bleeders each. The order (off the top of my head - it may be incorrect) is left inner, left outer, right inner, right outter, left front and right front.
Good luck. We have all been there!
LMJ
First - when they replaced the master cylinder, did they correctly bench bleed it? If not there is your answer.
Next, check all of your brake lines for possible leaks. Get some brakeclean and spray off any crud and check for possible pin holes, etc.
Usually, the problem you describe is due to what is called rotor run out. What that means is that the the brake rotors aren't truly perpendicular to the hub. This causes a small "wobble" which pumps the spring loaded calipers back and forth and actually pumps air into the calipers. The solution is to have a shop true up the rotors with a dial indicator to within .003 of true. Some people have had the rotors turned while on the car, but I can't speak for that. Believe me, it's for real and if you don't fix it you will lose your mind. Some high quality replacement calipers have double seals on the pistons to help prevent air entering as well.
Also remember there is an order to bleed the brakes and that the rear brakes have two bleeders each. The order (off the top of my head - it may be incorrect) is left inner, left outer, right inner, right outter, left front and right front.
Good luck. We have all been there!
LMJ
Drifting
Joined: Sep 1999
Posts: 1,908
Likes: 0
From: Manassas, VA, USA
Re: Very Weak and squishy brakes (L. Jackmin)
Corvette brakes can be a challenge, to say the least.
First - when they replaced the master cylinder, did they correctly bench bleed it? If not there is your answer.
Next, check all of your brake lines for possible leaks. Get some brakeclean and spray off any crud and check for possible pin holes, etc.
Usually, the problem you describe is due to what is called rotor run out. What that means is that the the brake rotors aren't truly perpendicular to the hub. This causes a small "wobble" which pumps the spring loaded calipers back and forth and actually pumps air into the calipers. The solution is to have a shop true up the rotors with a dial indicator to within .003 of true. Some people have had the rotors turned while on the car, but I can't speak for that. Believe me, it's for real and if you don't fix it you will lose your mind. Some high quality replacement calipers have double seals on the pistons to help prevent air entering as well.
Also remember there is an order to bleed the brakes and that the rear brakes have two bleeders each. The order (off the top of my head - it may be incorrect) is left inner, left outer, right inner, right outter, left front and right front.
Good luck. We have all been there!
LMJ
First - when they replaced the master cylinder, did they correctly bench bleed it? If not there is your answer.
Next, check all of your brake lines for possible leaks. Get some brakeclean and spray off any crud and check for possible pin holes, etc.
Usually, the problem you describe is due to what is called rotor run out. What that means is that the the brake rotors aren't truly perpendicular to the hub. This causes a small "wobble" which pumps the spring loaded calipers back and forth and actually pumps air into the calipers. The solution is to have a shop true up the rotors with a dial indicator to within .003 of true. Some people have had the rotors turned while on the car, but I can't speak for that. Believe me, it's for real and if you don't fix it you will lose your mind. Some high quality replacement calipers have double seals on the pistons to help prevent air entering as well.
Also remember there is an order to bleed the brakes and that the rear brakes have two bleeders each. The order (off the top of my head - it may be incorrect) is left inner, left outer, right inner, right outter, left front and right front.
Good luck. We have all been there!
LMJ
Melting Slicks
Joined: Oct 1999
Posts: 2,581
Likes: 14
From: Tolar Texas
Re: Very Weak and squishy brakes (lanceh007)
L. Jackmin summed it up pretty well but to learn even more regarding Corvette brakes go to Corvette Frequently Asked Questions.com. http://corvettefaq.com/
Forum member Terry Rudy is the web master. He has done a great job compiling a LOT of useful information.
Forum member Terry Rudy is the web master. He has done a great job compiling a LOT of useful information.
Melting Slicks
Joined: Mar 2001
Posts: 3,365
Likes: 5
From: Lake Villa IL
Cruise-In IV Veteran
Cruise-In V Veteran
St. Jude Contributor
Re: Very Weak and squishy brakes (lanceh007)
As R. Bruno said, the dealers don't know jack. You want to believe you're taking the Vette to the best place, but these guys who are working on your car, are experimenting. They haven't seen a C3, and probably never should. The technology is old. A lot of those guys are used to plugging a computer into a port, getting a code, and then looking up the code in the book to see what's wrong with the car.
If you aren't interested in doing the work yourself, find a competant Corvette mechanic. Ask around. Depending on where you are, some of the guys on this forum might be able to point you in the right direction.
And don't drive the car. If you need to pull over to pump the brakes, you shouldn't be on the road. Seriously. You're going to need them, and they aren't going to be there. Not to preach or anything, but nothing's worth getting hurt over. Park the car until you can get it fixed.
If you aren't interested in doing the work yourself, find a competant Corvette mechanic. Ask around. Depending on where you are, some of the guys on this forum might be able to point you in the right direction.
And don't drive the car. If you need to pull over to pump the brakes, you shouldn't be on the road. Seriously. You're going to need them, and they aren't going to be there. Not to preach or anything, but nothing's worth getting hurt over. Park the car until you can get it fixed.
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Racer
Joined: Nov 2001
Posts: 251
Likes: 0
From: Lake Hughes CA
Re: Very Weak and squishy brakes (R. Bruno)
Find a good vette, C3 guy to work on your car, don't bother with a dealer. Vette's are a different kind of animal. Even though it is a Chevy, I would bw willing to bet not one mechanic in the dealership has taken a course on C3 brakes. You will be lucky to find someone there who has even worked on a C3 before. C3's were last made 20 years ago. Very little of what makes a Vette different from a Capirce was carried over from a C3 to a C4. I feel this answers your most basic problem.... now on to the brakes!
I would agree with the run-out problem causing air to be pumped back into the brake lines. This is what is causing the brakes to be good for three days or so then die. Rather than screw with the stock calipers and trying to true the rotors (which would help for a while), replace the stock calipers with zero tolerance ones fron one of the vette vendors. But the calipers, put them on yourself and ask the folks here for advice on bleeding. If you get 4 different guys telling you how to do it, you will get at least five different answers and three will probably work fine :crazy:
As far as the pedal going to the floor with throttle, check your vacuum system. That sounds like a booster problem to me. What kind of vaciim do you pull at idle? Is your cam stock or aftermarket?
I would agree with the run-out problem causing air to be pumped back into the brake lines. This is what is causing the brakes to be good for three days or so then die. Rather than screw with the stock calipers and trying to true the rotors (which would help for a while), replace the stock calipers with zero tolerance ones fron one of the vette vendors. But the calipers, put them on yourself and ask the folks here for advice on bleeding. If you get 4 different guys telling you how to do it, you will get at least five different answers and three will probably work fine :crazy:
As far as the pedal going to the floor with throttle, check your vacuum system. That sounds like a booster problem to me. What kind of vaciim do you pull at idle? Is your cam stock or aftermarket?
