Quick Brake loss question...

[t78]

Hello everyone, (I know this is long, and I apologize... )

I just went through all of the posts related to brakes, and I still have a few questions.

On my new vette, I have the same problem of the brake going to the floor when I first stop, but if I pump it up - it holds better.

The other day while bleeding the brakes (to check for air), everything was going fine, until the last caliper I did (which was the right front). By buddy pumped them up, I opened the bleeder, he pushed down, I closed, he let up, just like the other three... But on this one, after the first bleed - the brake went very soft, wouldn't pump up any more, and the Emergency brake light came on...

I have tried to find out what the e-brake light means (when the e-brake is off), but havn't been able to. Any ideas?

Also, after that happened, I pulled the pads from the front right, and they were non-existant. It looked like the pistons were going in and out okay when we pushed the brake (so I think the caliper is still okay ?) , but the pad was so thin, it would not fill the gap between the caliper and rotor. I put new pads in, pushed the brake, and it was still soft, and the E-brake light was flashing.

I am going to attempt to bleed them good again tonight, but if any knows of the E-brake light being a bad warning sign, please let me know.


By the way, I have only had my vette for three weeks, and I love it. (I've only been able to drive it in and out of the garage though...) Even just vacuuming the inside gets me exicited I can't wait to cruise around town :0 You all have been a great help - and make things more fun!

t78

 

[redmist]

As I recall from the countless hours pouring over service manuals the emergency light is an indication that the because of pressure inequality between front/back systems that the brake propotioning valve has essentially shut down that system on which the offending caliper resides. I recall a procedure that involves applying significant pressure to the pedal after the problem has been fixed while bleeding the system in order to reset the proportioning valve.

I could be wrong though....best get Tom or Chris to confirm.

 

[69MyWay]

Brakes

You may already know this, but the best way to bleed brakes with a power assist brake system is with the engine running. If you are not doing it this way, you will never get a full deep bleed.

It is true you need to give the pedal several swift hard pumps with the engine running to get the valve to reset. You may need to bleed at the master cylinder.

BTW-There is a problem in your braking system to start with. Just bleeding it will only buy you some time. However, you may get lucky and find the prior owner never did a comprehensive job of bleeding the system. Check the inside of each tire for signs of fluid streaking on the tire. Trace the lines and look for any oily spots or signs of leakage.

You may have a bad master cylinder (recent problem on Nikki's 90). Maybe the prior owner has some service records you can review to keep from duplicating any recent work.

There was a recent post here where the owner found a bad hard line leaking. It pays to check it out.

 

[t78]

Think I got it fixed

Well, I think I got it fixed.
Thank you for all of the replies.

My friend came over, and we put new pads on, and bled the heck out of them. A lot of dark brown/black fluid was comming out, and we bled them until it cleared up. Now the break seems to hold up much better, and there is no more need to "pump it up".

I also checked each caliper while my friend was pumping (with ther tire off), looking straight down the rotor with a light I did not notice any leaks/fluid comming out from the center of the calipers.

When we were all done, I pumped and held the brake in a few times, and the E-brake light went out.

Hopefully everything is okay now.

Thanks for the advice,

-t78

 

[69MyWay]

T-78

Where in Jax are you? Do you belong to any local car clubs? I am out in Orange Park.

Hey, watch out on those brakes. Went through the same exact thing with my friend's 77. Then, we parked the car for a few weeks and only drove it around a little while we were working on the paint job.

Just finished painting it 01 Vette yellow. He spent a week or two putting all the trim and hardware back on the car. Decided to drive it to Church with his five year old son for the first time since we painted it. He was coming off of 9A to Phillips when he lost all of the brakes. Nearly had a major accident. Come to find out, the left front caliper (which we replaced several months before) was leaking just enough that he did not notice until is was almost too late. At least that is what we think at the moment.


Do you autocross? There is a major event coming up next weekend in Savanah. We are taking the 90 for a little solo II action. If you have those brakes licked, you should follow us up there and see what that 78 will do.

Chris

 

[Buckskin7T7V]

Pressure bleeding the system is the only way. You have too make sure the calibers are in good order. When the caliber is mounted high on the disk and at an angle, you will never get all of the performance out of the brake system. I also replaced the rubber brake lines with the branded stainless steel lines. It eliminates the expansion that the rubber brake lines have in them. This expansion lowers the pressure and there is a delay in the braking. I installed stainless steel calibers and that will help eliminate water corrosion that gets into the brake fluid.Do not use silicone brake fluid!! It will start to boil at altitude. If you go to the mountains (Rockies) it will start to boil-up.

 

[Hib Halverson]

Re: Brakes

You may already know this, but the best way to bleed brakes with a power assist brake system is with the engine running. If you are not doing it this way, you will never get a full deep bleed.

I'm not sure I agree with the above. I've been working on C2/3 disc brake systems since the early 1970s and I've never had the engine running on a power brake car to bleed sucessfully. Whether the power assist is working or not is not going to affect bleeding--unless there is something wrong with the power booster that prevents getting a full stroke out of the master cylinder.

I have found that in cases where there is a lot of air in the system that it is almost impossible to properly bleed the system without a pressure bleeder. I've also found bleeding goes easier if you jack the back up real high.

If the brake warning light is on and the emergency brake is *not* applied and there are no electrical problems with the e-brake switch, then one half of the braking system has a leak somewhere. It can be external or internal in the master cylinder.

If, during bleeding, you got a lot of really black or brown brake fluid, the system probably has a lot of grit and rust in it. That braking system needs to be overhauled, not just bled. This means replacing all the calipers with stainless steel sleeved units, rebuilding the master cylinder and flushing the lines.

There are two comprehensive articles on C2/3 disc brake service at:
http://www.idavette.net/hib/BBfHInet12.htm
and
http://www.idavette.net/hib/BBfHInet13.htm

 

[69MyWay]

I don't disagree. The power assist really helps the pedal pumper to get a good clean full stroke without a whole lot of effort. I have seen guys wear themselfs out trying to pump down the brakes without the assist kicking in.

There is no trick to it. Just makes the job go a little faster and a whole lot easier.

 

[Buckskin7T7V]

Thanks for the link. Learning something new is what we are here for.
Thanks again.

 

[iwannafly]

brakes and more brakes

Heres a situation I ran into a few years ago on my 77. Brakes would work fine for a while and then while sitting at a stop the pedal would slowly go the floor. After much searching and many changes of new master cylinders I finally discovered that one of the calipers was actually sucking air into the system. New one on my. I will remember it for a long time as it caused me many hours of frustration and labor.

 

[schnelkc74]

Just a quick note on bleeding vette brakes...
I had a lot of trouble bleading my brakes the conventional way, I never could get all of the air out of the lines. So I talked to a manager at a brake shop and asked him what I should do. He said that he would not do a pressure bleed on any car over about 15 years old, he said you'll just cause more problems. He told me that the way they would do it is by gravity bleeding. Which is just taking the top off of the master cylinder and opening the blead screw and letting gravity flow the fluid and air out of the lines (no pumping). Leave the screw open until it flows a steady stream of fluid. This does take a little more time than pumping the brakes, but you can do it yourself. I did this on my car and sure enough I got all of the air out.

 

[Crewzer]

Calipers

Corvette brakes are notoious for sucking air into the brake system. The caliper is a poor design and because the seal moves against the piston, run-out in the rotors can allow air to enter the system. Even worn rear wheel bearing can cause brake problems!

Crewzer

 

[Nut]

rotors?

t78,

I hope you resurfaced the rotors too when you replaced the pads. I neglected this recently and paid the price. The rotors were just slightly out-of-round. This caused the pistons to cavitate and suck air INTO the system. Resurface them, trued them to the bearing assy and voila!...... no more mushy pedal.

Regards........ Nut

 

[resto75]

Glad you have your brakes up and working right. Brakes can be important when you leave the garage. Now if we can get you away from that vacuum cleaner that excites you, you can get on the road. That will probably be more fun.