2003 Chevy S10 V6 Automatic 220,000 mi
Trying to fix a sinking brake pedal. No lights, no codes. No leaks, no loss of fluid. Replaced the master cylinder, bled everything by the book- no difference.Brake booster seems to be working fine. What’s going on? Could a faulty ABS module or pump cause this and if so, how?
More commonly it's the brake booster. But it can be the ABS. You'd have to have a fancy scan tool to test that though. Here's something you can do step on your break. If they're solid with the engine turned off and then you start the car and the brakes sink that's the booster going bad
@scottykilmer thanks for your advice, however after replacing the master cylinder (twice) and the brake booster the problem persists. I’ve read and watched numerous videos that say that if air gets trapped in the ABS module, sometimes it will only come out when the ABS pump is actuated with a high end scan tool (or by intentionally trying to skid a few times which I did)and the wheels are bled again. A lot of comments say this is total BS. Thoughts?
Thoughts?
Scotty doesn't usually revisit topics he has already answered. Most vehicles with ABS do require a sufficiently high-end scan tool to properly bleed the brake system, especially if air gets into the ABS module. For that truck it would be a GM Tech2 or scan tool with equivalent functionality.
Also make sure none of your rubber brake hoses are ballooning under pressure. Are they the 21-year-old originals?