Brake Problem...Help Please
Thread Starter
Racer
Joined: Jun 2002
Posts: 399
Likes: 1
From: LBL TN
Brake Problem...Help Please
My brother, the owner of a 67 vert calls me tonight seeking help.
Problem: The car pulls sharply to the left when the brake pedal is pushed and then shortly the right brake applies itself.
He has replaced lines, hoses, calipers, and pads. Bled the system.
Master cylinder is good. Put the car up on lift and there are no leaks
coming from any of the replaced parts stated above. No kinks or bends in line or hoses.
While on lift with both front tires spinning and when the brake pedal is pushed, the left brake stops immediately and the right tire spins 6 to 7 times and then it will stop.
I suggested to him it might be the proportioning valve. That is the only part in line that hasn't been replaced.
Anybody got any ideas that I can pass back to him tomorrow?
Thanks for reading.
Problem: The car pulls sharply to the left when the brake pedal is pushed and then shortly the right brake applies itself.
He has replaced lines, hoses, calipers, and pads. Bled the system.
Master cylinder is good. Put the car up on lift and there are no leaks
coming from any of the replaced parts stated above. No kinks or bends in line or hoses.
While on lift with both front tires spinning and when the brake pedal is pushed, the left brake stops immediately and the right tire spins 6 to 7 times and then it will stop.
I suggested to him it might be the proportioning valve. That is the only part in line that hasn't been replaced.
Anybody got any ideas that I can pass back to him tomorrow?
Thanks for reading.
Melting Slicks
Joined: Oct 2004
Posts: 3,345
Likes: 87
From: Northern MN
St. Jude Donor '13-'14-'15-'16-'17
The 67 does not have a proportioning valve. I am not sure what you would call it exactly but I call it a distribution block. Your brother has air in the line to the one that doesn't stop. He'll have to re-bleed the brake system. I had to do this because mine also pulled to the right when I first bled the system. I ultimately broke down and bought a Motive Bleeder. Best investment I made. You can bleed the brakes by yourself. No need to have someone else there pushing the pedal all the time.
Hope this helps.
Hope this helps.
Pro
Joined: Feb 2009
Posts: 589
Likes: 1
From: PA
New lines and hoses, nothing kinked so that's eliminate as the problem. No leaks so that means theres no air in the front brakes.
The right caliper grabs the its rotor so we can eliminate the master cylinder.
I would take the left wheel and tire off. Push the 4 pistons back a little off the rotor. Have someone push the pedal while someone else watches the pistons to see if they come out agaist the rotor. I'm suspecting the left caliper is at fault even though it's new.
The right caliper grabs the its rotor so we can eliminate the master cylinder.
I would take the left wheel and tire off. Push the 4 pistons back a little off the rotor. Have someone push the pedal while someone else watches the pistons to see if they come out agaist the rotor. I'm suspecting the left caliper is at fault even though it's new.
Melting Slicks
Joined: Oct 2004
Posts: 3,345
Likes: 87
From: Northern MN
St. Jude Donor '13-'14-'15-'16-'17
New lines and hoses, nothing kinked so that's eliminate as the problem. No leaks so that means theres no air in the front brakes.
The right caliper grabs the its rotor so we can eliminate the master cylinder.
I would take the left wheel and tire off. Push the 4 pistons back a little off the rotor. Have someone push the pedal while someone else watches the pistons to see if they come out agaist the rotor. I'm suspecting the left caliper is at fault even though it's new.
The right caliper grabs the its rotor so we can eliminate the master cylinder.
I would take the left wheel and tire off. Push the 4 pistons back a little off the rotor. Have someone push the pedal while someone else watches the pistons to see if they come out agaist the rotor. I'm suspecting the left caliper is at fault even though it's new.
No leaks doesn't mean "No Air In The System". If they just put the new hoses, lines, etc. and just bled the system, they still could have air in the line.
Pro
Joined: Feb 2009
Posts: 589
Likes: 1
From: PA
I been around Corvette's for over 30 years and have changed my fair share of brake calipers. I never got a bad rebuilt ss caliper, but anything is possible. Like a piece of dirt/rust blocking the passage way inside the caliper. No or little pressure getting to the pistons, no brakey brakey.
Last edited by 65747785; Jul 15, 2009 at 11:10 AM.
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Melting Slicks
Joined: Oct 2004
Posts: 3,345
Likes: 87
From: Northern MN
St. Jude Donor '13-'14-'15-'16-'17
I never said there couldn't be air in the system. But, with the right hand caliper grabbing its rotor there's no air in it. I did suspect there could be air still trapped in the left hand caliper. The guy said his brother bled the calipers, I have to think he bled them more than once.
I been around Corvette's for over 30 years and have changed my fair share of brake calipers. I never got a bad rebuilt ss caliper, but anything is possible. Like a piece of dirt/rust blocking the passage way inside the caliper. No or little pressure getting to the pistons, no brakey brakey.
I been around Corvette's for over 30 years and have changed my fair share of brake calipers. I never got a bad rebuilt ss caliper, but anything is possible. Like a piece of dirt/rust blocking the passage way inside the caliper. No or little pressure getting to the pistons, no brakey brakey.
I've been around them for over 30 years also. I just had this same thing happen to me after I got done re-installing me 66 MC on my car. When I went to drive it the car pulled to the right. I put the car back in the garage and re-bled the brakes with the help of the wife. Same problem. When I got the Motive Bleeder and re-bled them again I got air out of the right side front caliper.
Safety Car
Joined: Mar 2009
Posts: 4,191
Likes: 951
From: Corpus Christi, TX
If the car's been sitting unused for a while, you could also have a small leak in one or more of the caliper piston seals. This kind of leak will hold pressure, but with no pressure in the system brake fluid can drip out of the caliper and soak the brake pads. I've had that happen several times.
If this turns out to be your problem, in the future you might want to be sure to apply the brakes for a few seconds every week or so. Apparently the kind of seals used in C2/C3 calipers relax if they aren't pressured up every so often and this is what causes the leaks.
If this turns out to be your problem, in the future you might want to be sure to apply the brakes for a few seconds every week or so. Apparently the kind of seals used in C2/C3 calipers relax if they aren't pressured up every so often and this is what causes the leaks.
Thread Starter
Racer
Joined: Jun 2002
Posts: 399
Likes: 1
From: LBL TN
Thanks guys for the replies and input. I spoke with my brother this afternoon and directed him to this thread.
He appreciated you responses very much.
The proportioning valve is the only thing left that has not been replaced.
So he figures at this point, might as well spend the $99. for the valve.
We'll see what happens from there.
When the problem is solved I'll update you on this post.
Again, I want to thank you fellow forum members for responding.
That's why I have been on this site since 2002.
Terry in Tennessee
He appreciated you responses very much.
The proportioning valve is the only thing left that has not been replaced.
So he figures at this point, might as well spend the $99. for the valve.
We'll see what happens from there.
When the problem is solved I'll update you on this post.
Again, I want to thank you fellow forum members for responding.
That's why I have been on this site since 2002.
Terry in Tennessee
Pro
Joined: Feb 2009
Posts: 589
Likes: 1
From: PA
We're all trying to help with our suggestions and you already know that. It's just a simple matter for your brother to keep digging, he'll find the problem. That bugger of a problem is hiding somewhere, he'll find it.
Thread Starter
Racer
Joined: Jun 2002
Posts: 399
Likes: 1
From: LBL TN
Just wanted to update you guys. My brother called today and the "Proportioning Valve"
was indeed the culprit. Has been replaced and all is well.
Thanks everyone for your quick reponses and inputs.
Terry inTn
was indeed the culprit. Has been replaced and all is well.
Thanks everyone for your quick reponses and inputs.
Terry inTn
Team Owner
Joined: Oct 2000
Posts: 38,897
Likes: 1,926
From: Washington Michigan
Racer
Joined: Apr 2008
Posts: 439
Likes: 2
From: PASADENA CALIFORNIA
I have been thinking about this problem and what the final "Fix" was. I, as well as most of those who posted on this problem, were thinking that there was an imbalance in the front brakes upon application. I.E. one Front Brake would apply before the other or one front brake had more braking effort then the other, and the posts were directed toward a FRONT BRAKE Problem.
All I can think of, if in fact, the Proportioning Valve was the only thing that made a difference and no other repair had any effect, then there may have been a situation where you did not have any REAR BRAKES and this was corrected with the replacement of the Propotioning valve and/or the subsiquent bleeding of the entire system.
Without REAR BRAKES, a car can feel very unstable under braking. While most of the braking is done with the Front Brakes, the Rear Brakes will do some braking but also keep the car in a straight line and stable during braking. Without rear brakes, a car will want to go every which way under braking, especially hard braking. You can sucessfully operate a car with rear brakes only, except it will not stop very well, but not with front brakes only.
My Thoughts!
Chris, CWPASADENA
Last edited by CWPASADENA; Jul 25, 2009 at 06:38 PM. Reason: Typo
Racer
Joined: Apr 2008
Posts: 439
Likes: 2
From: PASADENA CALIFORNIA
You are absolutely CORRECT!
The owner was refering to the Distribution Block as a Proportioning Valve. I "wrongly" continued to do so to try to not confuse the issue any more then it had been.
I think what you say is exactly what happened.
Chris, CWPASADENA
Last edited by CWPASADENA; Jul 25, 2009 at 08:34 PM. Reason: Clarification