ABS Bleeding - air in system?
Thread Starter
Le Mans Master
Joined: Jan 2006
Posts: 5,621
Likes: 206
From: Orlando FL
ABS Bleeding - air in system?
If air should enter the ABS is a Tech 2 necessary for bleeding. If a system is power bled will it take the air out. Is there anyway way to activate ABS to pass fluid thru it.
I ask this question because this is an unknown factor in my brake problem. I have insufficient braking power with new master and system fully bled. Pedal travels fully with engine running. I just don’t think pads, rotors, booster or flex lines are the problem. Wondering if ABS could be a factor somehow. No codes, all systems normal, just low braking power.
I ask this question because this is an unknown factor in my brake problem. I have insufficient braking power with new master and system fully bled. Pedal travels fully with engine running. I just don’t think pads, rotors, booster or flex lines are the problem. Wondering if ABS could be a factor somehow. No codes, all systems normal, just low braking power.
Safety Car
Joined: Jul 2004
Posts: 3,835
Likes: 30
Originally Posted by pcolt94
If air should enter the ABS is a Tech 2 necessary for bleeding. If a system is power bled will it take the air out. Is there anyway way to activate ABS to pass fluid thru it.
I ask this question because this is an unknown factor in my brake problem. I have insufficient braking power with new master and system fully bled. Pedal travels fully with engine running. I just don’t think pads, rotors, booster or flex lines are the problem. Wondering if ABS could be a factor somehow. No codes, all systems normal, just low braking power.
I ask this question because this is an unknown factor in my brake problem. I have insufficient braking power with new master and system fully bled. Pedal travels fully with engine running. I just don’t think pads, rotors, booster or flex lines are the problem. Wondering if ABS could be a factor somehow. No codes, all systems normal, just low braking power.
i am posting this to "keep it all together"...
http://forums.corvetteforum.com/show....php?t=1382703
Thread Starter
Le Mans Master
Joined: Jan 2006
Posts: 5,621
Likes: 206
From: Orlando FL
Definitely bench bled the master. Back bled front and rear, cracked lines at master to get air out of lines. Then re-bled the lines again with the brake pedal being depressed. Then bled all cylinders. Same problem, not any better or worse. Obviously the old master was OK. Now I have two.
I have been reading the brake and ABS section in the GM books and have not found any special instructions that might address the ABS with special instructions. I have a good hard pedal with engine off, and normal pedal with engine on but with full travel if you push your foot down looking for that real panic stop breaking. I can drive the car normal, but this can’t be right, as it should be or when the car was sold.
I have been reading the brake and ABS section in the GM books and have not found any special instructions that might address the ABS with special instructions. I have a good hard pedal with engine off, and normal pedal with engine on but with full travel if you push your foot down looking for that real panic stop breaking. I can drive the car normal, but this can’t be right, as it should be or when the car was sold.
Safety Car
Joined: Jul 2004
Posts: 3,835
Likes: 30
Originally Posted by pcolt94
Definitely bench bled the master. Back bled front and rear, cracked lines at master to get air out of lines. Then re-bled the lines again with the brake pedal being depressed. Then bled all cylinders. Same problem, not any better or worse. Obviously the old master was OK. Now I have two.
I have been reading the brake and ABS section in the GM books and have not found any special instructions that might address the ABS with special instructions. I have a good hard pedal with engine off, and normal pedal with engine on but with full travel if you push your foot down looking for that real panic stop breaking. I can drive the car normal, but this can’t be right, as it should be or when the car was sold.
I have been reading the brake and ABS section in the GM books and have not found any special instructions that might address the ABS with special instructions. I have a good hard pedal with engine off, and normal pedal with engine on but with full travel if you push your foot down looking for that real panic stop breaking. I can drive the car normal, but this can’t be right, as it should be or when the car was sold.
Thread Starter
Le Mans Master
Joined: Jan 2006
Posts: 5,621
Likes: 206
From: Orlando FL
Just for fun I took my front rotors off (with little ware) and decided to break the glaze just incase it was part of the problem. Took the drill with a emery rotor disk and did all 4 surfaces. Came out pretty nice even got rid of the slight outside edge that forms. Sanded the new pads slightly and re-assembled. No real improvement but at least the rotors are in better shape.
I then unbolted the M/C just to see if the booster rod was really coming out and pushing hard on the M/C piston or to see anything strange. Booster seems to be normal and so is it’s operation.
Re-bled the fronts again for fun about 15 pumps getting clear fluid. Pedal still real hard and normal as one would consider.
I keep coming back to the point of how far the darn piston is traveling into the M/C when the engine is running when I push down hard. Where the heck is all that fluid going. The calipers don’t move that much that should allow the displacement of that much fluid. If someone told me this I would tell them they had air in the system. It’s like the flex brake lines are ballooning absorbing the pressure but I don’t see anything abnormal. I just don’t think there is enough hydraulic pressure in the system to stop the car normally.
I then unbolted the M/C just to see if the booster rod was really coming out and pushing hard on the M/C piston or to see anything strange. Booster seems to be normal and so is it’s operation.
Re-bled the fronts again for fun about 15 pumps getting clear fluid. Pedal still real hard and normal as one would consider.
I keep coming back to the point of how far the darn piston is traveling into the M/C when the engine is running when I push down hard. Where the heck is all that fluid going. The calipers don’t move that much that should allow the displacement of that much fluid. If someone told me this I would tell them they had air in the system. It’s like the flex brake lines are ballooning absorbing the pressure but I don’t see anything abnormal. I just don’t think there is enough hydraulic pressure in the system to stop the car normally.
Last edited by pcolt94; May 22, 2006 at 02:23 PM.
Instructor
Joined: Apr 2005
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MC problem
You probably have a leak between the front and rear seal in the MC itself. (Bad MC) Rebuild it or get a new one.
It sounds like it is allowing the fluid to blow past the seals as the pedal goes down. The fluid isn't going anywhere but back into the resevoir.
The brake booster makes it a lot easier to push the pedal so that is why they are hard when the engine is not running.
try bleeding them with the engine running so you can put some pressure on the system.
have you ever tried to stop a car with no vacume pressure at the booster? The don't work half as good as manual brakes because they need the booster to work. That is why it is hard to make pressure to bleed them with the car off. Be careful opening the hole when it is running. It will shoot out like a firehose.
The best way is to use a power bleeder.
It sounds like it is allowing the fluid to blow past the seals as the pedal goes down. The fluid isn't going anywhere but back into the resevoir.
The brake booster makes it a lot easier to push the pedal so that is why they are hard when the engine is not running.
try bleeding them with the engine running so you can put some pressure on the system.
have you ever tried to stop a car with no vacume pressure at the booster? The don't work half as good as manual brakes because they need the booster to work. That is why it is hard to make pressure to bleed them with the car off. Be careful opening the hole when it is running. It will shoot out like a firehose.
The best way is to use a power bleeder.
Thread Starter
Le Mans Master
Joined: Jan 2006
Posts: 5,621
Likes: 206
From: Orlando FL
The master is a new factory unit and is the exact same problem as the one removed. It was bench bled before installation. I am aware and agree with the rest of you information.
I did power bleed the system this weekend followed by a regular bleeding. No change in brakes although they might have got a little better when I sanded the rotors.
I have been back bleeding brakes and clutches for years. I have this weird idea now. Remove the master, extend the lines in the car to outside the car and into a bucket. Then power back bleed all calipers. There should be almost no resistance to the flow and any air should come flying out with the big flow. Any air should naturally move up from the wheels and ABS to the front of the car. I don’t know if it will solve anything but I think it is a great idea.
I did power bleed the system this weekend followed by a regular bleeding. No change in brakes although they might have got a little better when I sanded the rotors.
I have been back bleeding brakes and clutches for years. I have this weird idea now. Remove the master, extend the lines in the car to outside the car and into a bucket. Then power back bleed all calipers. There should be almost no resistance to the flow and any air should come flying out with the big flow. Any air should naturally move up from the wheels and ABS to the front of the car. I don’t know if it will solve anything but I think it is a great idea.
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Thread Starter
Le Mans Master
Joined: Jan 2006
Posts: 5,621
Likes: 206
From: Orlando FL
This info from a previous post;
The brake pedal does not ever sink, it is hard but I can push it down to the floor with one foot (engine running, standing still). There are no leeks anywhere nor do I ever add fluid. With engine off pedal is like a rock and does not sink. Vacuum booster will hold vacuum long time or till you pump 3 or more times and then gets hard. Changed front pads on principal, rears still OK. Have bleed all 4 wheel cylinders normally for air.
The classic symptom, the sinking brake pedal is not exhibited. I’m thinking the brake booster is OK.
Since then I have;
Bench bled the new master. Back bled both front and rear to force air out at M/S fittings. Re-bled fittings using brake pedal. Bled all wheel cylinders. I'm back where I started.
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The pedal is hard with the engine off which is normal. With running it feels rather normal but I can push to full travel. While driving you seem to run out of brake.
The brake pedal does not ever sink, it is hard but I can push it down to the floor with one foot (engine running, standing still). There are no leeks anywhere nor do I ever add fluid. With engine off pedal is like a rock and does not sink. Vacuum booster will hold vacuum long time or till you pump 3 or more times and then gets hard. Changed front pads on principal, rears still OK. Have bleed all 4 wheel cylinders normally for air.
The classic symptom, the sinking brake pedal is not exhibited. I’m thinking the brake booster is OK.
Since then I have;
Bench bled the new master. Back bled both front and rear to force air out at M/S fittings. Re-bled fittings using brake pedal. Bled all wheel cylinders. I'm back where I started.
-----------------------
The pedal is hard with the engine off which is normal. With running it feels rather normal but I can push to full travel. While driving you seem to run out of brake.
