2007 Avalanche brake problem

[whitestingray81]

My apologies for posting this in the Tahoe/Yukon forum, but the Avalanche forum gets very little traffic.

I've had my 2007 Avalanche for 13 months now. 1 month ago it failed inspection for rear brakes. Turns out the passenger side rear inboard pad was worn all the way down to metal. The rest of the pads had a good amount of material left. I replaced the pads myself with Duralast Gold (ceramic) pads, and lubed the guide pins with silicone grease. Also replaced the pad retainer clips myself. I then went on a road trip where I put around 1000-1200 miles on the car. About half-way into the trip, I noticed a chattering, or vibration throughout the entire car, while I was backing out of an inclined parking spot. I've gotten it to do it again a few times since, but it doesn't happen every time. It happens when I drive the car for a while, park, then come back a few minutes later. Always at slow speed only.

So I decided to pull off the pads again and take a look. It looks like the same pad that had no friction material left is now wearing a grove into the pad. Here's a picture of the old pad:



And this is the new pad I pulled off after the road trip:



As you can see I think the chattering or vibration is from the grooves in the pad. What would cause this? Rotors or caliper? Caliper bore moves fine when I push it in to put on the new pads. I didn't notice anything weird and the rotor doesn't looks scored or damaged at all.

According to the carfax, the rear pads were changed at 46k miles, and the rotors were resurfaced for a second time then as well. Car currently has 93k miles on it.

So I guess I need to know if it's time for a new caliper, or time for new rear rotors? All help is much appreciated. Thanks!

 

[ulakovic22]

Have your local parts house mic your rotors and see if they are in spec. Two turns at less than 100k seems a little much. If the rotor is smooth with no ridges then clean the pad up and try again. I don't think its the caliper, your pads look good.

 

[whitestingray81]

Yeah, I thought it was a bit much too. Unfortunately the carfax doesn't have the mileage on the first turn, but new pads and turn at 47k? That seems early, and new pads less than 45k again? Can a bad rotor cause the inside pad to wear prematurely?

I have a set of digital calipers. Any idea of what the minimum thickness is? Would it make sense just to measure 10 or so random spots on the rotor to see if the thickness is uniform?

Thanks for the help!

Have your local parts house mic your rotors and see if they are in spec. Two turns at less than 100k seems a little much. If the rotor is smooth with no ridges then clean the pad up and try again. I don't think its the caliper, your pads look good.

 

[joshcarl]

the minimum thickness is usually stamped into the rotor itself. i'm leaning more towards an internal issue in the caliper. there are rebuild kits available at Advance for less than $10, and complete calipers for ~$50. i'd suggest a complete rear overhaul with new rotors, pads, and either a new caliper or a rebuild. make sure the grease you're using on the pins is for brakes. the heat generated by braking can cause other lubricants to fail.

good luck and send us the results!

 

[ulakovic22]

+1 on the min tolerance being stamped on the rotor.

The pad wear looks uniform and the caliper should center itself when the piston is extended. I'd check the pins to make sure the caliper is able to freely slide back and forth.

 

[whitestingray81]

The slide pins move freely and have been lubed with dielectric grease to hopefully keep them that way. I don't think it's the slide pins.

There are noticeable groves on the old and new pad. Sorry for the poor pictures. You can see them with the naked eye and you can certainly feel them. Maybe 1-2mm deep. I tried to highlight them in this picture:



But regardless, I have a feeling that it's time for rotors, as well as a caliper. Ugh...

 

[Wake]

Check the caliper brackets themselves.

I had couple of pads dragging and I ended up cleaning the rust out of the pocket where the pad clips go into the caliper bracket.

I noticed the pad didn't move freely, like it was being squeezed from the ends. I probably took out about 1/32" or so of rust between the two ends. I used a file, smoothed it down where the rust was raised and flaking inside the bracket pocket, painted and reassembled. No more issues since.

 

[08grey]

Could be a warped rotor. Most older shops will cut your rotor for lime 25 dollars. I would cut the rotor and see what happens. BTW if you get a acdelco caliper paint it before you install it. They rust bad.

 

[whitestingray81]

I think you're on to something. I noticed the inboard pad was difficult to take out and get back in. If it's too snug in there it will absolutely hang up! Thanks for the idea. I'm going to do that next and see if it remedies it.

Check the caliper brackets themselves.

I had couple of pads dragging and I ended up cleaning the rust out of the pocket where the pad clips go into the caliper bracket.

I noticed the pad didn't move freely, like it was being squeezed from the ends. I probably took out about 1/32" or so of rust between the two ends. I used a file, smoothed it down where the rust was raised and flaking inside the bracket pocket, painted and reassembled. No more issues since.

 

[whitestingray81]

Just wanted to give an update. I replaced the caliper bracket with a rebuilt one, which included new slide pin seals. The pad seems to move a bit more freely than before.

Also replaced the caliper slide pins and bolts with new ones from AC Delco, and lubed everything with silicon grease. So far so good, but I haven't driven it much. I'll report back if anything new arises. Thanks again for all the help!