91 Corvette ABS problems.
Thread Starter
Instructor
Joined: Aug 2009
Posts: 149
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91 Corvette ABS problems.
I have a 1991 Corvette that has an ABS issue. When you first start the car the ABS light will come on and you will hear a grinding in the back from the ABS unit but also the brake pedal goes to the floor and you can feel the grinding in the pedal itself. This will go on and off usually 3 to 5 times while you're driving in the fist five minutes. After that everything works fine until you shut it off and then it all starts again. Contemplated changing all the ABS sensors but I don't know if that will have any effect on the pedal going to the floor. The pedal going to the floor is what baffles me the most. This almost seems like maybe there is air in the system? Any suggestions would be appreciated. I had the car sold but this ABS issue stopped the sale so I have to get it fixed. Have a 79 and a 76 I want to work on but need to sell this car to get the money to work on the other two.
Safety Car
Joined: Sep 2010
Posts: 3,752
Likes: 190
From: Indiana PA
Which ABS light? ABS active? Or the ABS fault light?
Sounds like the self test is not performing properly. Should happen at low speeds under 10mph the first time you start to move after start up.
Pedal is going to the floor because the system is dumping pressure in the system.
Sounds like the self test is not performing properly. Should happen at low speeds under 10mph the first time you start to move after start up.
Pedal is going to the floor because the system is dumping pressure in the system.
Advanced
Joined: Jan 2013
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Which ABS light? ABS active? Or the ABS fault light?
Sounds like the self test is not performing properly. Should happen at low speeds under 10mph the first time you start to move after start up.
Pedal is going to the floor because the system is dumping pressure in the system.
Sounds like the self test is not performing properly. Should happen at low speeds under 10mph the first time you start to move after start up.
Pedal is going to the floor because the system is dumping pressure in the system.
Agree...i think you can get the unit to cycle with a tech 1...at least i did with my 94 (its stiil obd 1). That will tell you and dump the codes.You can dump the codes manually but the cycle test pinned it down for me. Luckily I knew a guy with a tech 1.
A go to floor pedal usually doesn't fix itself if its a traditional brake "SYSTEM" problem.
Thread Starter
Instructor
Joined: Aug 2009
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I remembered when I put new rotors on that I didn't bleed the brakes very good because one of the bleeder screws would not budge. I ended up taking that caliper off and finally got the valve out and replaced it. Then ran all new brake fluid in it and bled the system. After that the ABS light only came on once and it didn't go to the floor, but on the second day, after stopping and starting the car about 5 times, it started doing it again. The light will come on multiple times, sometimes as long as 5 seconds or more, and the pedal dropped a couple times but not every time. The ABS Service light never comes on, just the ABS light and you can hear it working behind the driver seat.
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Safety Car
Joined: Jun 2010
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One other opinion, your pump might be having issues. The pump should only do a self check once per key cycle and that is when it hits 4 mph in forward or reverse. If you are getting multiple cycles it could be losing power or ground.
I would definitely bleed again.
Drifting
Joined: Jul 2009
Posts: 1,258
Likes: 99
From: Ashland PA
2021 C4 of the Year - Modified Finalist
you need to activate the pump with a teck 1 well bleeding,if that does not fix it then you need to perform the tests with the teck 1 or some other compatible test equipment to see what the problem is.