96 chevy k1500 abs bleeding?

[BDaugherty]

1996 Chevy K1500 Z71 350/auto 4wheel abs. I recently did some brake work on a z71 because the rear brakes were extremely touchy. The left rear would lock up at the slightest touch of the brake pedal. The right rear was covered in gear oil from a leaking wheel seal. I changed the wheel cylinders, brake shoes, wheel seals, and front pads. Then I bled the system with a pressure bleeder and the old school pedal pump way. The shoes are adjusted up tight against the drums for sure and I ran a quart of brake fluid through the system AFTER I stopped getting any air. Problem is, I still have a very spongy pedal and while the brakes work, they aren't great. I have driven it enough that I feel that the new pads and shoes should be seated enough for that to not be an issue. I tried to command the ABS to cycle while pressure bleeding the brakes, but there was no option to turn the ABS on using my Snap-On Modis scan tool. Has anyone had experience with these systems? What am I missing? I've done some internet searching that has led me to think that the problem is either air in the ABS module or trash in an ABS accumulator valve. I'm not real sure how firm the brakes were prior to the repair, but there's no way it's good enough the way it is now.

 

[mwilson]

1996 Chevy K1500 Z71 350/auto 4wheel abs. I recently did some brake work on a z71 because the rear brakes were extremely touchy. The left rear would lock up at the slightest touch of the brake pedal. The right rear was covered in gear oil from a leaking wheel seal. I changed the wheel cylinders, brake shoes, wheel seals, and front pads. Then I bled the system with a pressure bleeder and the old school pedal pump way. The shoes are adjusted up tight against the drums for sure and I ran a quart of brake fluid through the system AFTER I stopped getting any air. Problem is, I still have a very spongy pedal and while the brakes work, they aren't great. I have driven it enough that I feel that the new pads and shoes should be seated enough for that to not be an issue. I tried to command the ABS to cycle while pressure bleeding the brakes, but there was no option to turn the ABS on using my Snap-On Modis scan tool. Has anyone had experience with these systems? What am I missing? I've done some internet searching that has led me to think that the problem is either air in the ABS module or trash in an ABS accumulator valve. I'm not real sure how firm the brakes were prior to the repair, but there's no way it's good enough the way it is now.

'97 Caddy, same deal.





My Remedy was this.....



Take it out to a safe location and do a couple of panic stops (gravel surface works the best). Hard enough to activate the ABS pump. You will feel the pedal firm up after a couple of tries. That is the only way around a trip to the dealer that I have found. Had my Town & Country's pull the same thing after complete brake line replacements.



After the panic stops take it back to the shop and bleed the wheels again. That should do it.



This has been my experience and cure for three different vehicles now. If you can't make the ABS Pump cycle with the scan tool then this is the only other way to make the pump run and it's internal valves open so that the air can escape.



Worth a try. .



Mike.

 

[BDaugherty]

You're on a roll with the help today, Mike. I'll try the shadetree abs maneuver.

 

[NIsaacs]

I had the same problem with a Jeep Grand Cherokee, getting the air out of the abs pump. I jacked up the rear, run that sucker up to about 70 and slammed the brakes on several times. The light came on and I bled the rear, then did the 70 and slammed the brakes on again, the abs light went off and all was well.



Nick

 

[JR]

Your not missing a proportioning valve with a bleeder on it by chance are you? I've overlooked them on different vehicles in the past and had similar issues.