86 corvette brakes not releasing completely:(
03-20-2012, 09:16 PM
#1
4th Gear
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86 corvette brakes not releasing completely:(
Hello, I have a 1986 corvette convertible with brake problems. The rear wheels do not release completely all the time. On one occasion they held so tight that the car started to overheat trying to get it to my repair shop
. I noticed it when i stopped at a red light and although the car was in drive it was not inching forward when i released the brake. I have had two different mechanics check the vehicle and they could not determine if was the abs relay, the abs pump. or the abs control module. Anybody can help me here. I love the car but its not fun when you are afraid the brakes are not working correctly Larry azflcowboy in florida
. I noticed it when i stopped at a red light and although the car was in drive it was not inching forward when i released the brake. I have had two different mechanics check the vehicle and they could not determine if was the abs relay, the abs pump. or the abs control module. Anybody can help me here. I love the car but its not fun when you are afraid the brakes are not working correctly Larry azflcowboy in florida
03-21-2012, 10:34 AM
#5
Melting Slicks
Can't you just pull a fuse for the ABS to take it offline and see what happens? Is it both rear wheels or just one?
I would think its probably something simple like the parking brake. The master could be the culprit as well as the booster.
A bad caliper or a bad brake hose could be the cause if its just one wheel. I had that happen on a car once and it turned out to be a collapsed hose not allowing the pressure to be released once the pedal was up. How old is the brake fluid?
I would think its probably something simple like the parking brake. The master could be the culprit as well as the booster.
A bad caliper or a bad brake hose could be the cause if its just one wheel. I had that happen on a car once and it turned out to be a collapsed hose not allowing the pressure to be released once the pedal was up. How old is the brake fluid?
03-21-2012, 09:52 PM
#6
Safety Car
I rebuilt the brakes on an old vert I had and both the front brake hoses collapsed. Never crossed my mind and I kept going back thru everything I had done until a mechanic suggested the hoses. Not saying its your problem but if everything else checks out keep it in mind.
03-22-2012, 10:24 AM
#7
Melting Slicks
I rebuilt the brakes on an old vert I had and both the front brake hoses collapsed. Never crossed my mind and I kept going back thru everything I had done until a mechanic suggested the hoses. Not saying its your problem but if everything else checks out keep it in mind.
03-22-2012, 11:30 PM
#8
Race Director
How long has it been since you changed brake fluid?
Old brake fluid gets thick and will cause the pistons to hang up in the calipers (happened to me on a Honda motorcycle).
Old brake fluid gets thick and will cause the pistons to hang up in the calipers (happened to me on a Honda motorcycle).
03-23-2012, 12:02 PM
#9
Drifting
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Yup, I've learned my lesson. I used to always jump to the most complicated diagnostic when in reality it was something simple. I think we've been conditioned in the past 15 years with the computer controls in our cars to think its the complicated electronics and systems that fail when really, its just the normal wear and tear things. I had a 99 Cadillac, I know what I am talking about.
03-23-2012, 03:17 PM
#10
Melting Slicks
Yup, the 99 had the revised engine but it still was an oil burner and noisy when cold not to mention needed 91 octane. I will say with 275 HP and that thing moved. Shame the cost of a rebuilt NorthStar is more than the car is worth. I sold it when the StabiliTrac started spitting codes. I had had enough at that point.
03-01-2013, 04:09 PM
#11
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Hi there
Thank you for all your input concerning my 1986 corvette with the rear brakes grabbing
1. i did have the emergency brake checked and that was not the problem
2. the first garage i took it to pumped out all the old brake fluid and replaced the brake fluid...that was not the problem they told me to take it to the chevy dealer and be prepared to pay big time, the mechanic thought it was the ebcm and that was very expensive.
3. i took it to my corvette mechanic in pompano beach, florida i drove it there from clermont , florida 200 miles away... where i live. He had it for 4 days and he said the problem was an adjustment to the master brake power booster, he adjusted it and when i drove away i could still feel the brakes holding especially when i stopped at a red light, the car would NOT inch forward when i let off the foot brake brought it back and he said it was the ebcm and they were very expensive and he would call me if he could find one for less that $1,000 dollars....he never called back and did not return my calls i suspect he gave up will not go back there again...when i was a policeman there he treated me great...now that i am retired he apparently does not need my business
4. i took it to another shop and they disconnected the brakes and they said it was hard to turn the rear wheels with the rear brakes disconnected when the car was up on the lift so they said the rear differential was the problem and it would cost over $1500 to remove and rebuild the rear differential.
5. drove it away and another mechanic i ran into at hobby lobby who works for the local chevy dealer said the ebcm's do not go bad that often he suggested i change the rear brake lines since they were 27 years old and needed to be replaced anyway and that could be the problem since the brakes grabbing was intermittent....when the brakes are not grabing/binding the car is a dream to drive and i love her (kathleen is her name the car is a red convertible with 86 k miles
6. any other suggestion folks i do plan to change the brake lines, i guess i can buy them locally at any local parts store?
thanks again az fl cowboy Larry
Thank you for all your input concerning my 1986 corvette with the rear brakes grabbing
1. i did have the emergency brake checked and that was not the problem
2. the first garage i took it to pumped out all the old brake fluid and replaced the brake fluid...that was not the problem they told me to take it to the chevy dealer and be prepared to pay big time, the mechanic thought it was the ebcm and that was very expensive.
3. i took it to my corvette mechanic in pompano beach, florida i drove it there from clermont , florida 200 miles away... where i live. He had it for 4 days and he said the problem was an adjustment to the master brake power booster, he adjusted it and when i drove away i could still feel the brakes holding especially when i stopped at a red light, the car would NOT inch forward when i let off the foot brake
brought it back and he said it was the ebcm and they were very expensive and he would call me if he could find one for less that $1,000 dollars....he never called back and did not return my calls i suspect he gave up will not go back there again...when i was a policeman there he treated me great...now that i am retired he apparently does not need my business4. i took it to another shop and they disconnected the brakes and they said it was hard to turn the rear wheels with the rear brakes disconnected when the car was up on the lift so they said the rear differential was the problem and it would cost over $1500 to remove and rebuild the rear differential.
5. drove it away and another mechanic i ran into at hobby lobby who works for the local chevy dealer said the ebcm's do not go bad that often he suggested i change the rear brake lines since they were 27 years old and needed to be replaced anyway and that could be the problem since the brakes grabbing was intermittent....when the brakes are not grabing/binding the car is a dream to drive and i love her (kathleen is her name
the car is a red convertible with 86 k miles6. any other suggestion folks i do plan to change the brake lines, i guess i can buy them locally at any local parts store?
thanks again
az fl cowboy Larry
03-01-2013, 05:23 PM
#13
Pro
Just a couple of thoughts, the rear axle is a posi so it can take just one brake hanging up to hold the axle. Are any of the rotors starting to turn blue? if so I would suspect that wheel as the problem. Another thing to try is open the bleeders one at a time to see if that releases the brake or reduces the drag. If it does the hose on that wheel is a potential culprit, if it does not than it could be the caliper and further testing would be needed. How about the fronts, why do you suspect the rears?
Gary
Gary
Last edited by yd328; 03-01-2013 at 05:26 PM.
03-01-2013, 07:24 PM
#14
Melting Slicks
The ABS can NOT apply the brakes or hold them. I cannot stress this enough. Do not listen to anyone who wants you to start throwing ABS parts at it.
03-01-2013, 07:27 PM
#15
Melting Slicks
Further, the ECM has nothing to do with the ABS. Who are these moron "mechanics"?
03-01-2013, 07:34 PM
#16
Drifting
I had a vehicle doing the same thing. After changing out the disks, the brake calipers and pads, nothing was fixed. I found a suggestion on line that said it could be the rubber brake lines. I replaced it and it fixed the problem. Just a thought.
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yakmastermax (09-15-2023)
03-01-2013, 08:03 PM
#17
Melting Slicks
If the booster has an internal leak it can put pressure on the brakes, the rod between the booster and the master cylinder needs to be adjusted correctly for the master cylinder piston to return all the way back. If the master cylinder piston does not release all the way back it will prevent your brake calipers releasing (both front and rear)
The brake hoses can swell up and restrict fluid when they get old, also you may need to check the calipers are not rusted inside and seizing.
I would check the following first.
Raise both rear wheels of the ground and check the wheels turn freely with trans in neutral, check the park brake works apply while someone turns the wheels and release and check wheels turn freely.
Then turn the wheels and depress the brake pedal (engine off) make sure that the brakes work and that the wheels release when brake pressure is released.
Now remove the abs fuse and start the engine in neutral and see if the wheels turn, (the trans will apply some force to wheels in neutral so use brake to stop the rotation before shifting to park) if they do not the booster may be at fault if it has an internal leak that causes the pedal to drop slightly (a common thing in all cars).
If the wheels turn apply the foot brake and release check they will still rotate freely afterwards, as a previous poster said the ABS cannot apply the brakes think of them as a solenoid valve that can release pressure in pulses when it sees a wheel is about to stop.
The ABS relies on the driver to depress the brakes and lock the brakes up, the ABS sole function is to prevent a complete stop of one or more wheels for more than a given length of time.
It does this by measuring the speed sensors and will detect differences between the speeds of each wheel.
By removing the abs fuse the car will be as any other non ABS car and you will lock the wheels, do this for the tests only and refit them. Any experienced mechanic should have no issue finding the problem... the diff is a limited slip that means if your car is in neutral and one wheel of the ground it will take a lot of force to rotate the wheel usually around 150 ft pounds of torque.
That is why you need to have both wheels of the ground.
Hope this info helps you narrow it down.
I see it as 5 things that can be at fault
1 booster has an internal leak hole in diaphragm (start engine and note if pedal drops a little)
2 Master cylinder not returning due to booster or rod between booster not adjusted correctly
3 Brake caliper piston seized rusted
4 Brake hose swollen and blocking of internally.
5 Handbrake over adjusted you can check this by how far you can pull the park brake handle
Note a rusted half shaft universal joint can restrict rear wheel turning, usually they will make plenty of clicking squealing noise well before that.
The brake hoses can swell up and restrict fluid when they get old, also you may need to check the calipers are not rusted inside and seizing.
I would check the following first.
Raise both rear wheels of the ground and check the wheels turn freely with trans in neutral, check the park brake works apply while someone turns the wheels and release and check wheels turn freely.
Then turn the wheels and depress the brake pedal (engine off) make sure that the brakes work and that the wheels release when brake pressure is released.
Now remove the abs fuse and start the engine in neutral and see if the wheels turn, (the trans will apply some force to wheels in neutral so use brake to stop the rotation before shifting to park) if they do not the booster may be at fault if it has an internal leak that causes the pedal to drop slightly (a common thing in all cars).
If the wheels turn apply the foot brake and release check they will still rotate freely afterwards, as a previous poster said the ABS cannot apply the brakes think of them as a solenoid valve that can release pressure in pulses when it sees a wheel is about to stop.
The ABS relies on the driver to depress the brakes and lock the brakes up, the ABS sole function is to prevent a complete stop of one or more wheels for more than a given length of time.
It does this by measuring the speed sensors and will detect differences between the speeds of each wheel.
By removing the abs fuse the car will be as any other non ABS car and you will lock the wheels, do this for the tests only and refit them. Any experienced mechanic should have no issue finding the problem... the diff is a limited slip that means if your car is in neutral and one wheel of the ground it will take a lot of force to rotate the wheel usually around 150 ft pounds of torque.
That is why you need to have both wheels of the ground.
Hope this info helps you narrow it down.
I see it as 5 things that can be at fault
1 booster has an internal leak hole in diaphragm (start engine and note if pedal drops a little)
2 Master cylinder not returning due to booster or rod between booster not adjusted correctly
3 Brake caliper piston seized rusted
4 Brake hose swollen and blocking of internally.
5 Handbrake over adjusted you can check this by how far you can pull the park brake handle
Note a rusted half shaft universal joint can restrict rear wheel turning, usually they will make plenty of clicking squealing noise well before that.
03-12-2013, 12:57 PM
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1986 corvette brakes binding , not releasing
Thank you guys, you all are great
I am working on the advice you all gave me and I am confident that your advice will help me cure this beautiful 86 convertible
Thank you , thank you again;
Larry azflcowboy at ya who dot com
I am working on the advice you all gave me and I am confident that your advice will help me cure this beautiful 86 convertible
Thank you , thank you again;
Larry azflcowboy at ya who dot com
