Brakes Quit Working

[Mynyrd1]

Yesterday i had to hit the brakes kind of hard - after thatt he pedal went to the floor. Can't find any leaks the master cylinder is full. Power steering fluid looks ok. flushed power steering fluid about a year ago.

Thanks for your help.

[rapidoxidationman]

My first guess would be a blown seal on the master cylinder piston. What happens if you open up a brake caliper bleeder and push the pedal? Should be a strong stream of brake fluid coming out.

What year truck?

[Mynyrd1]

2005 K3500 Crew Cab Dually
Didn't have a chance to check anything under the truck mechanically.
It snowed a few inches here(Twin Cites MN) had to clear snow.
Going to look at it tonight.

There is no resistance on the pedal at all. I was thinking master cylinder but thought it would be pretty strange for both the front and the rear to fail at the same time.

From what I have read so far it sonds like the Hydra Boost.

As I find out I will keep posting.

[DmaxMaverick]

With no pedal resistance at all, it's likely a mechanical failure outside the hydroboost and master cylinder. Check the brake pedal linkage. Even if it were the hydroboost unit that's failed, hydraulically, the brakes should still work, with increased pedal resistance. There is no mechanical disconnect between the pedal input at the HB unit and the master cylinder. It's a straight-line throughput, from the HB input to the MC input, steel to steel to steel. The parts are very robust, so it would take a significant catastrophic failure before the throughput were interrupted and brakes failed completely.

Another possibility, although slight, is the ABS. Try the brakes with engine off, then with engine on and ABS fuse pulled. The ABS module should be passive with no control power, and do nothing. However, with no brake pressure, front or rear, the problem is much more likely at a common point of failure, such as the brake pedal linkage before the HB unit.

[Mynyrd1]

Well found my problem. The line broke down by the controller on the frame. Chevy has a "pipe" kit with all the lines pre-bent for $103.00.

Should be here Friday.

[topfueler1]

Good to hear you got it figured out.