Brakes are now dragging??
Thread Starter
Melting Slicks
Joined: Jun 2011
Posts: 2,096
Likes: 15
Brakes are now dragging??
First off sorry to keep bothering everyone but don't have a clue where to turn. Last summer I installed Wilwood calipers on my 82 b/c the factory ones kept leaking even after getting replacements. Well after all the bleeding they were really never any better. Now recently I decided to replace the master cylinder thinking this is the problem so I replaced it with a Wilwood unit.
I've bled the m/c twice and the system many times and even had the rear calipers in the more upright position. Felt like I was getting somewhere and the brakes are now too good, so good that they are now dragging. What has happened? I did notice If I pull up on the brake pedal while driving it slightly gets better and also when you press on the brake and release the pedal it returns slowly with the car running. It feels like it's the rears that are dragging b/c it causes the back end of the car to squat.
Please help I'm desperate and ready to get this brake thing behind me.
I've bled the m/c twice and the system many times and even had the rear calipers in the more upright position. Felt like I was getting somewhere and the brakes are now too good, so good that they are now dragging. What has happened? I did notice If I pull up on the brake pedal while driving it slightly gets better and also when you press on the brake and release the pedal it returns slowly with the car running. It feels like it's the rears that are dragging b/c it causes the back end of the car to squat.
Please help I'm desperate and ready to get this brake thing behind me.
2026 Loser of the Year
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From: New Or-leens Loo-z-anna
If it helps by pulling up the brake pedal, the small rod between the master cylinder and the brake booster may be too long (1/16" or so) which causes the plunger inside the master cylinder to keep fluid pressure on the caliper pistons (per Forum experts who have advised me).
Then the pads heat up and grab even if the brake pedal is not pushed.
Then the pads heat up and grab even if the brake pedal is not pushed.
Thread Starter
Melting Slicks
Joined: Jun 2011
Posts: 2,096
Likes: 15
If it helps by pulling up the brake pedal, the small rod between the master cylinder and the brake booster may be too long (1/16" or so) which causes the plunger inside the master cylinder to keep fluid pressure on the caliper pistons (per Forum experts who have advised me).
Then the pads heat up and grab even if the brake pedal is not pushed.
Then the pads heat up and grab even if the brake pedal is not pushed.
Melting Slicks
Joined: Jul 2010
Posts: 3,176
Likes: 633
From: perth western australia
If it helps by pulling up the brake pedal, the small rod between the master cylinder and the brake booster may be too long (1/16" or so) which causes the plunger inside the master cylinder to keep fluid pressure on the caliper pistons (per Forum experts who have advised me).
Then the pads heat up and grab even if the brake pedal is not pushed.
Then the pads heat up and grab even if the brake pedal is not pushed.
It also could be a combination of the pin and a worn return spring on your brake pedal .
Thread Starter
Melting Slicks
Joined: Jun 2011
Posts: 2,096
Likes: 15
I second this, to make sure this is not your problem , put the car on level ground , hand brake off and in neutral and just (try to?) push it. if its hard to push then grab a spanner and loosen off the master from the brake booster and just pull it clear and try again , if it rolls easy then its THAT pin being too long .
It also could be a combination of the pin and a worn return spring on your brake pedal .
It also could be a combination of the pin and a worn return spring on your brake pedal .
Racer
Joined: Mar 2016
Posts: 470
Likes: 31
From: Melbourne Victoria
You need to test it on a level surface and do it in neutral not drive. Maybe you could even sit in the car and put it in neutral with a 3% incline. If it doesn't move get someone to give you a little push.
Last edited by Corvetteoz; Jan 24, 2017 at 05:23 PM.
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Thread Starter
Melting Slicks
Joined: Jun 2011
Posts: 2,096
Likes: 15
When the car is cold it drives like normal but within a couple mikes the rears heat up and pulls the car down. I could barely back in the drive when I came home from my drive. Put the rear in the air and removed the tires and couldn't bulge the rotors so I cracked the bleeder and was able to turn them. It's only the tears. Could it be "run out "? Out of spec?
Safety Car
Joined: May 2004
Posts: 4,366
Likes: 1,589
From: los altos hills california
I'm sort of still following this. There's a console light that is supposed to let you know if there is a pressure imbalance. That light connects to the brass manifold where all your lines meet.. Even if your bulb is burned out you probably could hook up a voltmeter. It probably supplies a ground so measure resistance but that just guessing on my part.
It is curious.
Run out typically pumps up the cylinders in the caliper with air.
Ya know, there are a couple of bolts that fasten the rear caliper in place that are too long for the Willwoods and as i remember I had to shim them with washers to avoid contact with the rotor. Have a look at that. It probably would leave some scoring which you can't see and make some noise. I suppose after a while the problem would go away sort of as the metal ground down.
https://www.corvetteforum.com/forums...post1589661678
What you say about cracking the bleeders kind of negates that as a theory, but ...
It is curious.
Run out typically pumps up the cylinders in the caliper with air.
Ya know, there are a couple of bolts that fasten the rear caliper in place that are too long for the Willwoods and as i remember I had to shim them with washers to avoid contact with the rotor. Have a look at that. It probably would leave some scoring which you can't see and make some noise. I suppose after a while the problem would go away sort of as the metal ground down.
https://www.corvetteforum.com/forums...post1589661678
What you say about cracking the bleeders kind of negates that as a theory, but ...
Last edited by ignatz; Jan 24, 2017 at 06:46 PM.
Thread Starter
Melting Slicks
Joined: Jun 2011
Posts: 2,096
Likes: 15
I'm sort of still following this. There's a console light that is supposed to let you know if there is a pressure imbalance. That light connects to the brass manifold where all your lines meet.. Even if your bulb is burned out you probably could hook up a voltmeter. It probably supplies a ground so measure resistance but that just guessing on my part.
It is curious.
Run out typically pumps up the cylinders in the caliper with air.
Ya know, there are a couple of bolts that fasten the rear caliper in place that are too long for the Willwoods and as i remember I had to shim them with washers to avoid contact with the rotor. Have a look at that. It probably would leave some scoring which you can't see and make some noise. I suppose after a while the problem would go away sort of as the metal ground down.
It is curious.
Run out typically pumps up the cylinders in the caliper with air.
Ya know, there are a couple of bolts that fasten the rear caliper in place that are too long for the Willwoods and as i remember I had to shim them with washers to avoid contact with the rotor. Have a look at that. It probably would leave some scoring which you can't see and make some noise. I suppose after a while the problem would go away sort of as the metal ground down.
The car is free to push around when the brakes are cold easy actually but after just down the road drive they are heating up and grabbing to the point where it feels like you are power braking. I might already have said but I cracked open the bleeder on one of the sides ( I think pass.) and it free'd the rotors because I could turn them grabbing the lug nuts. Could that be a clue to something different?
Safety Car
Joined: May 2004
Posts: 4,366
Likes: 1,589
From: los altos hills california
You could isolate the problem to the master cylinder by reinstalling the original. Of course then you have to bleed the the whole damn thing again.
You could also buy a pressure gauge that plugs into the bleeder and see if you have residual pressure after pushing down on the brakes with the engine running. They are kind of pricey so maybe your local auto parts store has a loaner?
If you use the gauge you want the down bleeder not the up bleeder as you'll otherwise get air back into the lines.
You could also buy a pressure gauge that plugs into the bleeder and see if you have residual pressure after pushing down on the brakes with the engine running. They are kind of pricey so maybe your local auto parts store has a loaner?
If you use the gauge you want the down bleeder not the up bleeder as you'll otherwise get air back into the lines.
Last edited by ignatz; Jan 24, 2017 at 07:03 PM.
Thread Starter
Melting Slicks
Joined: Jun 2011
Posts: 2,096
Likes: 15
Hmm good suggestions I'll look for a gauge. Another thing is the brakes are extremely touchy and maybe that's why they are grabbing?? I thought about loosing the m/c and placing washers for spacers thing maybe the m/c rod is too long although it the same dimensions as the stock m/c??
Last edited by alconk; Jan 24, 2017 at 08:30 PM.
Le Mans Master
Joined: Dec 2007
Posts: 6,422
Likes: 591
From: McHenry Illinois
Have you tried loosening the 2 nuts that hold the master cylinder to the booster? I know you said the rod is not adjustable, so it seems like the rod from the booster to the pedal may be adjusted too tight. As master cylinder piston megins to move, it blocks the return port to the reservoir, then begins to move fluid to the calipers and make pressure. If when the pedal is released and the master cylinder piston does not come back enough to uncover the return port to the reservoir then pressure will be trapped and cause the brakes to drag. Or like mentioned above, your pedal return spring may be weak.
Melting Slicks
Joined: Jul 2010
Posts: 3,176
Likes: 633
From: perth western australia
Hmm good suggestions I'll look for a gauge. Another thing is the brakes are extremely touchy and maybe that's why they are grabbing?? I thought about loosing the m/c and placing washers for spacers thing maybe the m/c rod is too long although it the same dimensions as the stock m/c??
Thread Starter
Melting Slicks
Joined: Jun 2011
Posts: 2,096
Likes: 15
I went ahead and cut off the booster rod 1/8th " and put everything back together. Haven't had a chance to bleed yet. Guys at Wilwood say if they are dragging and if you open the bleeder screw and fluid comes out then the rod is too long. So we'll see.
Safety Car
Joined: May 2004
Posts: 4,366
Likes: 1,589
From: los altos hills california
A couple of observations:
If it is the fact that only the rears were dragging because of a minor length disparity, that would suggest the rears start to engage before the fronts. That characteristic would be designed into the MC. Probably wouldn't matter much, but still seems kind of odd.
And, back when I had some issues with my Willwoods I put two pressure gauges on the car, one in the front and one in the back. I saw no timing disparity but I will go back and look at the video I took.
Finally, I can't get in my car to look right now, but I am wondering what the stop on the brake pedal return looks like. If there is any adjustment capability it would seem to be an easier fix. I don't know what the leverage gain is, however so 1/8" x gain might be a lot.
Hope this works out for the OP, so many headaches but I have to say having made a couple of emergency stops, these are great brakes, especially considering the design is a half century old. I've been wanting to measure my 70:0 stopping distance but weather is not cooperating and I haven't figured out a way to do it really accurately.
If it is the fact that only the rears were dragging because of a minor length disparity, that would suggest the rears start to engage before the fronts. That characteristic would be designed into the MC. Probably wouldn't matter much, but still seems kind of odd.
And, back when I had some issues with my Willwoods I put two pressure gauges on the car, one in the front and one in the back. I saw no timing disparity but I will go back and look at the video I took.
Finally, I can't get in my car to look right now, but I am wondering what the stop on the brake pedal return looks like. If there is any adjustment capability it would seem to be an easier fix. I don't know what the leverage gain is, however so 1/8" x gain might be a lot.
Hope this works out for the OP, so many headaches but I have to say having made a couple of emergency stops, these are great brakes, especially considering the design is a half century old. I've been wanting to measure my 70:0 stopping distance but weather is not cooperating and I haven't figured out a way to do it really accurately.
Thread Starter
Melting Slicks
Joined: Jun 2011
Posts: 2,096
Likes: 15
Well I think I got it saying that loosely.. No more dragging but the brakes feel no different than when I first started I guess. Maybe better but wouldn't be much. I can't get the rears to lock up?? Should they with the fronts? When I get my pressure gauge I will compare the pressure. from the front to the rears although I was told the rears will be less. Thank you everyone for the comments and suggestions.
AL
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