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Mike V.
Mike V., Auto Technician
Category: Chevy
Satisfied Customers: 23827
Experience:  25 years automotive experience, Certified Subaru Tech and Nissan factory trained.
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1997 chev k1500, 5.7, auto trans: Replaced calipers, bled

Customer Question

1997 chev k1500, 5.7, auto trans: Replaced calipers, bled lines. Good pedal with engine off, sinks to the floor when I start the engine. The truck stops, antilock function is working-- the rapid pulses and the intermittent wheel almost lock-ups on gravel road. Seems to work on all wheels, but the pedal is almost not there at all. Is there a way to bleed the Kelsy-Hayes ABS controller without the scan tool?
Submitted: 1 year ago.
Category: Chevy
Expert:  Mike V. replied 1 year ago.

Hi there,

Was this an issue prior to the caliper replacement?

Customer: replied 1 year ago.
No.
Expert:  Mike V. replied 1 year ago.

Ok, this may seem silly, but please check and make sure the bleeder screws on the calipers are pointed up. What I see a lot is the calipers accidentally on the wrong side. When this happens you can bleed them and you will have a great pedal when the vehicle isn't running, but start it and the pedal drops. This is because the air rises up to the top. If the bleeder isn't up top, then there is still air in the calipers. It is easy to swap sides by mistake.

Please look at this and let me know.

Customer: replied 1 year ago.
Calipers are correctly positioned. list any other questions to rule out my making a stupid mistake all together.
Expert:  Mike V. replied 1 year ago.

As far as simple mistakes that is really it.

Now, this system should be cross bled. Starting with the rr, lf, lr and rf. In that order. If this has been done or doesn't resolve the issue, then I would line lock the brake hoses on the new calipers. Then start the truck and press the brake pedal and see if it's firm. You should not have to bleed the ABS unless you let the master cylinder run dry while changing the calipers. It is however quite possible you got a bad replacement caliper. If you line lock them and the pedal is firm, remove them one at a time until the pedal drops to the floor. Then I would replace that caliper. If the pedal is soft right from the get go, then you will need to start by bleeding the master cylinder. This can be done right on the truck. I suspect however you are going to find one of the new calipers defective or a brake pad not lined up properly.

Check these and let me know.

Customer: replied 1 year ago.
Howdy, I had to do something else, now I'm back to the truck. Master cylinder is bled. Calipers both function, pads are not misaligned. I still have good, hard pedal until I start the engine, then pedal promptly sinks to the floor. My question Is there a way to bleed the Kelsy-Hayes ABS controller without the scan tool? was prompted by multiple Do-It-Yourself sites that seem to be less than complete about individual systems. The ABS module on mine has two input lines and three output lines (output side splits the two front wheel controls). The articles that I read described the front wheel hydraulic circuits as open to normal bleeding, but that the rear circuit is not and that the pump(s) must be homed and dump valves cycled to purge. I also tried bleeding the lines at the output fittings with engine running and my helper putting slight pressure on the pedal. Still the same symptom of good pedal with engine off, sinks to the floor upon starting engine.
Expert:  Mike V. replied 1 year ago.

Did you try line locking one of the front to make sure one of the calipers is not the cause?
I know of no way to bleed the system without the scan tool, but just don't feel confident it's the problem. I have seen so many of the rebuilt calipers have problems I feel it's an important step.

Customer: replied 1 year ago.
Sorry, they were salvage yard parts, which had to be retracted to install. I applied light brake pressure and could not rotate the front wheels (up on jackstands). they rotate freely when no brake applied. I don't know how I would line lock-- the term is unknown to me.
Expert:  Mike V. replied 1 year ago.

Ok, take a pair of vise grips and pinch off the rubber hoses to the calipers. There is also a rear line to the axle. Do them all at the same time and start the truck. If the pedal feels good, then you have eliminated the master cylinder and the ABS as the culprit. Then, remove one line lock at a time. When the pedal drops to the floor, you have found the bad part. Then, if you find it's one to the calipers, swap it with another.

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