trouble with 04 avalanche

[Jester1]

This is about a weird problem I have never encountered. 04 avalanche 5.3 fully loaded if this helps.

It seems while driving that the brakes lightly apply themselves. It "seems" to occur around 55-60 miles an hour. As you apply more gas they seem to get tighter. I just got back from California driving to and from and it didn't happen at all on the trip. 1 day later wife is telling me about it and at first I thought she was a.nuts or b.it had gone into limp mode (neither is true...yet) Nothing comes up on the dash info and will release once you come to a full stop.

Only thing I can think of is it does have hydro boost master and possibly has gone bad as the pressure increases upon acceleration. As far as I know it does not have an active electronic braking system other than abs which I believe is passive monitoring.

Anybody hear of such a thing and know of the remedy? I know that sometimes pulling the ecm fuse for a while can reset any problems but as i said not throwing any codes so leads me to think mechanical not electric.

Thanks

 

[Jester1]

Also seems to be all brakes not just one as it doesn't pull or drag to any one side.

 

[diesel4me]

I've seen a few vehicles that had similar symptoms (brakes seem to "drag" or apply themselves,the further you drive it the tighter they get),and it was due to the master cylinder not having a tiny bit of "free play" between the piston in it and the little push rod that operates the piston when you step on the pedal..some push rods are adjustable ,some aren't..sometimes a gasket od spacer between the master cylinder and the mounting surface on the booster determines the free play..

The brake fluid expands when it gets hot,without any free play there,eventually the piston in the master gets pressure applied to it enough to apply the brakes some,the fluid gets hotter,and the cycle repeats until they wont let the wheels roll freely...if a caliper or wheel cylinder drags,that too can cause the fluid to expand and self apply the brakes,but you'd most likely feel it pulling to that side,and it'd affect that one brake mostly too..