brake/abs problem
Thread Starter
Burning Brakes
Joined: Jun 2009
Posts: 1,135
Likes: 226
From: Roanoke Indiana
brake/abs problem
Drove my 89 today for the 1st time this season. The abs reset as usual, but the pedal felt harder than I remembered. Drove it about 10 miles to lunch. On the way back home I felt the car downshifting more than normal, then realized the brakes weren't releasing. Drove it about 1/4 mile. It started to smell hot. The left front brake was smoking, but the all seemed hot. It tracked straight, so I think it was all of them. After about 15 min they released. Had it brought home on a flat bed.
Can ABS cause the brake not to release? Any suggestions how to fix this?
Can ABS cause the brake not to release? Any suggestions how to fix this?
Race Director
Joined: Mar 2015
Posts: 15,926
Likes: 579
Drove my 89 today for the 1st time this season. The abs reset as usual, but the pedal felt harder than I remembered. Drove it about 10 miles to lunch. On the way back home I felt the car downshifting more than normal, then realized the brakes weren't releasing. Drove it about 1/4 mile. It started to smell hot. The left front brake was smoking, but the all seemed hot. It tracked straight, so I think it was all of them. After about 15 min they released. Had it brought home on a flat bed.
Can ABS cause the brake not to release? Any suggestions how to fix this?
Can ABS cause the brake not to release? Any suggestions how to fix this?
Thread Starter
Burning Brakes
Joined: Jun 2009
Posts: 1,135
Likes: 226
From: Roanoke Indiana
not fixed yet
Still having the problem. Last year after flushing the brakes, the ABS light stayed on. After some research the most likely point of failure seemed to be a relay that was no longer available, so I replaced it with a 12v relay and the ABS light went out. After my problem this spring I bought a good used relay. Test drove it today for about the same 10 miles. Stopping frequently. The brakes seemed to start dragging about 1 mile from home and gradually get worse. Got to the end of my driveway and they were as tight as before. Front rotors were 250* and the rears were 185*. loosened the master cylinder, no change. Cracked the left front bleeder expecting the fluid to spray out. It didn't just a little came out as I would expect from a car just sitting there.
After that the wheels moved.
Anyone know how to remove this system? This car is driven about 1000 a year now. Has 62k miles on it. Never driven in wet conditions and not driven aggressively. I doubt ABS has ever been activated.
After that the wheels moved.
Anyone know how to remove this system? This car is driven about 1000 a year now. Has 62k miles on it. Never driven in wet conditions and not driven aggressively. I doubt ABS has ever been activated.
Thread Starter
Burning Brakes
Joined: Jun 2009
Posts: 1,135
Likes: 226
From: Roanoke Indiana
Race Director
Joined: Mar 2015
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Then pull the valve and clean and inspect
Race Director
Joined: Mar 2015
Posts: 15,926
Likes: 579
Is your brake boster working if the brakes are hard that might be something to look at pump up the brake with the key off hold the brake down and start the car the pedal should give a bit I think
Last edited by antfarmer2; Jun 6, 2015 at 11:48 AM.
Thread Starter
Burning Brakes
Joined: Jun 2009
Posts: 1,135
Likes: 226
From: Roanoke Indiana
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Thread Starter
Burning Brakes
Joined: Jun 2009
Posts: 1,135
Likes: 226
From: Roanoke Indiana
Dismantled the front calipers lubed the sliders and reassembled them.
If I apply the brakes, engine off, and turn the rotors by hand, they turn harder than I think they should. If I crack the bleeder, they turn much easier. I was thinking Master cylinder, then read on another forum that sometimes the hoses fail and act like check valves. Since they are original, I'll try replacing them.
If the ABS has a problem, it doesn't know it. Runs the test at start up and no light.
If I apply the brakes, engine off, and turn the rotors by hand, they turn harder than I think they should. If I crack the bleeder, they turn much easier. I was thinking Master cylinder, then read on another forum that sometimes the hoses fail and act like check valves. Since they are original, I'll try replacing them.
If the ABS has a problem, it doesn't know it. Runs the test at start up and no light.
Team Owner
Joined: Sep 2003
Posts: 25,388
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You mentioned "flushing" last year and I just assumed that with a 25+ year old car you would have done the hoses. It would seem odd that you would have multiple hose failures but anything is likely. It will be much easier to diagnose I'd think with the hoses just hanging and with the convenience of the lift not that difficult.
Thread Starter
Burning Brakes
Joined: Jun 2009
Posts: 1,135
Likes: 226
From: Roanoke Indiana
You mentioned "flushing" last year and I just assumed that with a 25+ year old car you would have done the hoses. It would seem odd that you would have multiple hose failures but anything is likely. It will be much easier to diagnose I'd think with the hoses just hanging and with the convenience of the lift not that difficult.
some times things get away from me. Just replaced an 18 year old battery in my Cobra replica. (still worked fine) Yeah, I thought of that to (both front hoses at the same time) but maybe they didn't like vacuum bleeding. I have to start somewhere.
Burning Brakes
Joined: Jun 2005
Posts: 1,189
Likes: 13
From: Wallingford Vermont
I would test the Brake Booster operation. Real simple: disconnect the vacuum line from the Booster diaphragm (plug it so your Vette will run). Now go for a test ride. YOU WILL HAVE NO POWER ASSIST AND IT WILL TAKE A LOT MORE PEDAL EFFORT TO STOP - DRIVE ACCORDINGLY. If you don't experience the brake dragging problem, you've found your culprit. 
Race Director
Joined: Mar 2015
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Thread Starter
Burning Brakes
Joined: Jun 2009
Posts: 1,135
Likes: 226
From: Roanoke Indiana
Team Owner
Joined: Sep 2003
Posts: 25,388
Likes: 2,741
There is an "internal" to the master cylinder proportioning control valve and YES that's correct terminology of the internal one.