01 Gmc 2500 Hd Brake Problem.

[Chuck2500HD]

I have a 2001 GMC 2500 HD 4x4 with the 8.1 and allison combo. Went out this morning in the snow and went to stop and the abs kicked in then the pedal went straight to the floor like it blew a brake line. But I don't think that is what happened. The fluid reservoir is still full and the brakes work at the bottom of the pedal travel and the ABS still works but has no power assist. And the weird thing is there are no warning lights on. To me it seems like a booster issue but this truck doesn't have a vacuum booster but some sort of compressor on the side of the master cylinder. Don't know much about this type of brake system. Anybody have any ideas?

 

Thanks!

Chuck

[gmtech4]

read the ABS in your owners manual,

 

the pedal does go down as it dumps brake fluid for you to maintain steering .

 

no lights=no probs.

 

i think you're fine

[Chuck2500HD]

read the ABS in your owners manual,

 

the pedal does go down as it dumps brake fluid for you to maintain steering .

 

no lights=no probs.

 

i think you're fine

 

 

If that were true the pedal feel should have returned to normal immediately but it still just goes right to the floor before anything happens. It's acting like it's not able to build brake pressure back up or something.

[markw8]

The system is called hydaboost. They use this I think mostly because the diesels don't make vacuum to power a booster. Possibly also, more boost in a smaller package.

 

Mark

[Chuck2500HD]

It does have the Hydraboost system that is run off the power steering pump. Don't know much about this type of system. Pedal still goes to the floor real easy and comes back up real slow. Do you know what any potential problems can be?

[markw8]

It does have the Hydraboost system that is run off the power steering pump. Don't know much about this type of system. Pedal still goes to the floor real easy and comes back up real slow. Do you know what any potential problems can be?

 

Sorry, I can't really help with your problem, If it's abs related a dealer or someone with a tech 2 should be able to retreive codes. I've not had problems with either of mine.

 

Mark

[Chuck2500HD]

Figured I would update this. Finally got around to working on the truck and found that on both rear calipers the pistons had seized and would not return on their own when pressure was taken off the brake pedal. When I got the pistons freed up and went to test I found brake fluid spraying out of one brake line just below the front of the drivers door on the frame rail. All the lines running through that area were rusted pretty bad. Ended up with all new brake lines and rear calipers. Sprung for the coated lines so hopefully they don't rust out anytime soon.