SureTrack Community Fix: Panic Works for Once

Real Fixes from ShopKey’s SureTrack® expert information resource are documented issues from actual shop repair orders and community discussions. Read on to see how SureTrack can help you correct issues that are not easily diagnosed using OEM information alone. SureTrack is currently available free with the purchase of a current Snap-on® diagnostic software version or in our ShopKey Pro product.

Sometimes it takes an unusual procedure to get the job done, especially when you can’t find any other solution. SureTrack community member erick01 had a Chevrolet S10 pickup in the shop with a soft brake pedal and after several bleedings, the pedal would still go to the floor. They posed the question to the community, and with the help of fellow community member ironnutz, and others, they were able to resolve the issue quickly.

The following Community Fix summarizes the interaction between members of the community that led to the solution.

1996 Chevrolet S10 Pickup 4.3L

Soft brake pedal with engine running. Repeat bleeding procedure.

Firm brake pedal with engine off. Pedal slowly drifts to floor with engine running. With engine running, the rear chamber of the master cylinder bubbles constantly while brake pedal is being pushed.

Diagnostic Steps Performed/Parts Replaced
Installed two new master cylinders. Brake booster is fine. Blocked the lines off after the equalizer and before the abs unit and the pedal stays firm. There is no way to energize the ABS unit with my scanner because it is an early production 1996 model. Module mounted on coolant tank. Bleeding brakes in sequence and there are no leaks. Have run 3 large bottles of brake fluid through it and there is no air in the lines. Need way to energize the ABS unit to help with the bleeding.

Best Answer from Community Member ironnutz
Do some panic stops in gravel to get the ABS to activate, then bleed again. Sounds more like a booster issue. Pinch off the vacuum hose to the booster, start it up and see if the pedal still fades.

Air trapped in ABS system preventing complete bleeding.

Tried suggested panic stops and then bleeding system until problem was corrected. Booster was not at fault.

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About the Author

Nick Taylor

Nick Taylor is the SureTrack Community Administrator and a Senior Applications Specialist at Mitchell 1 with over 25 years of experience with electronic repair data systems. Nick previously worked in the automotive dismantling and engine rebuilding industries.