Right front brake sticking, inconsistently (Avalanche 2500)

[RussMcB]

Pals,

I have a 2002 Chevrolet Avalanche 2500 and the brakes have not been great forever, like, often pulling to one side suddenly.

The most obvious culprit is a sticking caliper, but I've replaced them, along with rotors, pads and fluid. That helped for a while, but a few months later the problem is back. When I drive I get a slight pull to the right (even without applying the brakes), a hot front hub, can smell brakes, etc. Luckily it's usually only a slight drag, not keeping me from getting somewhere, but at times has been closer to locked up.

It's possible I got a poorly rebuilt caliper from the auto parts store. I plan to remove the caliper and work the pistons in and out to see if any are sticking.

Could it be a brake line, or master cylinder? It seems odd that only one front brake is affected.

Any other suggestions? Thanks in advance.

[reidhazelton]

I'd replace the soft lines. When those get old and spongy they can do weird things. 20 years old makes it seem quite possible.

Also, it is possible you got a bad caliper. The "rebuild" process isn't exactly in a high quality control environment.

[Rick Kirchner]

not pistons - slide pins.

But if it's been doing it since the calipers were replaced, I wonder if it's an ABS controller problem - like holding pressure in the line.

[DaveW]

I'd replace the soft lines. When those get old and spongy they can do weird things. 20 years old makes it seem quite possible...

^ This.

Old lines can delaminate inside and a flap of the delamination can block fluid flow, especially back to the reservoir because that has less pressure behind it.

[Garey Guzman]

Russ,
I work in this area for my day job and can go into more detail via email if you need.

Is the pull constant? Various roads have various amounts of road crowning so it's important to be aware of it during your testing. You said it's causing excess heat - what's the temp differential between sides? Is the slight pull only during braking or also during coasting (in gear and in neutral).

If the caliper is not releasing completely, it's most likely due to sticky slide pins on the floating caliper. If replacing helped, it is possible that re-lubing the slide pins will resolve the issue. My company has a Moly grease for this, probably the same for other manufacturers.

From my experience, neither the hoses or master cylinder can cause this issue on a modern street car. Most modern m/c output lines feed 1 front and 1 rear wheel each, to minimize brake pressure loss in the event of losing a brake line or a chamber of the m/c. If it was a hose issue, replacing calipers wouldn't have resolved it at all. There is a very, very slim possibility that it could be internal valving in the ABS control unit but that's very unlikely since the caliper replacement helped temporarily. An air bubble in the ABS unit is possible, which would be bounced out by engaging ABS a few times (like on a dirt road), then bleeding.

[RussMcB]

Thanks, all. Great thoughts.

Stupid truck, I took it for a test drive a few minutes ago (haven't changed anything yet) and now it's pulling to the left when applying the brakes. Like, the right front caliper wasn't doing anything. I didn't drive it far enough to see if a constant drag was present.

I'll order new soft lines since the truck is getting old. Won't hurt, might help. I'll check the pistons and sliders, too. I'll report back in a week or so, after I've had a chance to get in there. Thanks, again.