[Green98K1500]

I'm the original owner of a stock 98K1500 (290K original miles). Everything was normal until pulling onto the shoulder of the road yesterday onto some leaves < 25MPH; the ABS kicked in and I stopped without incident. After that, the brakes were soft all the way home, and the problem persists. I could slow the truck by pumping them but if I maintain pressure on the pedal, it goes to the floor. I cannot find any leaks, the fluid level is full, & no OB codes @ brakes on the scanner.
Any help would be appreciated.

 

[Rambodog]

"The ABS system uses a series of solenoids and valves to redirect fluid flow. A set of valves (solenoid valves/isolation valves) are responsible for isolating the brake pedal from the rest of the brake system during an ABS event. If the ABS unit activates but does NOT isolate the brake pedal, the brake fluid will flow directly into the the accumulator, a spring-loaded brake fluid container for ABS systems. This lets the pedal sink to the floor.

If the brake pedal sinks to the floor only when the ABS unit activates, then your isolation valves may be the problem".

 

[GMT604]

Bleed the brakes and see if they improve. It's possible that someone had the system open and didn't bleed them properly to get the air out of the ABS, and that was the first time the ABS activated since. Could also be the master cylinder failed.

 

[Green98K1500]

Thanks,

It looks like I may have to take it into a brake shop; I'll look for the isolation valve.

The 60 AMP fuse looks OK.

The master cylinder and booster were replaced 5 years ago; no new changes to the system.

But I will check everything I can find.

Thanks again.

 

[Green98K1500]

The problem was the master cylinder; thanks for the help folks!

G