Issue with rear calipers

Barbatio

Original poster
Member
Jun 8, 2021
5
Ohio
I've got a problem with my rear brakes that has me stumped. About 4 months ago I started to hear a squealing noise coming from the rear so I got some brake pads while in town. When I went to change the rear brake pads in my 05 Envoy I noticed a strange pad wear. The pad that sits against the piston of the caliper was worn way down and the outside pad still had plenty of life left on it, this was the same on both the passenger and driver side. Asking a question in a group I got told that I needed to, "Grease every part of the caliper including the slide pins and to use 'Silicone grease' so it helps keep to rubber soft." Following this I went ahead and replaced the brake pads making sure to clean the slide pins and the bores before replacing them and stuffing them full of silicone grease. And here I am 4 months later, I did my rear sway bar end links and while back there I looked at the pads only to see the same wear pattern.

So to sum up
  • The piston side of both rear calipers is keeping pressure on the pads even after releasing the brakes, causing the inner pads to wear down very quickly.
  • The calipers are well lubed using 'Silicon Brake Lube' (Recommended to keep the rubber soft).
  • This is the second occurrence despite pad replacement 3-4 months ago.
Any possibly ideas as to what might cause the calipers to not release after the brakes have been release?

Pulled from another forum because I couldn't get any suggestions there.
 

6716

Member
Jul 24, 2012
821
I just replaced a rear caliper for this exact reason, and it seems to have fixed the issue. Yes, you need to lubricate the slides, but if the caliper piston itself sticks and won't release back a little into the caliper, you get this uneven wear. I had some brake noise/squeak as well since the piston kept the pad against the rotor.

You don't "have to" get a whole new caliper, actually, you can pull the caliper and "do the maintenance" on the piston. You can get a new piston and new seals, and lube it an put it all back together in the caliper body but I didn't feel like doing all that so I went and got a remanufactured one at the parts store.
 
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Barbatio

Original poster
Member
Jun 8, 2021
5
Ohio
I just replaced a rear caliper for this exact reason, and it seems to have fixed the issue. Yes, you need to lubricate the slides, but if the caliper piston itself sticks and won't release back a little into the caliper, you get this uneven wear. I had some brake noise/squeak as well since the piston kept the pad against the rotor.

You don't "have to" get a whole new caliper, actually, you can pull the caliper and "do the maintenance" on the piston. You can get a new piston and new seals, and lube it an put it all back together in the caliper body but I didn't feel like doing all that so I went and got a remanufactured one at the parts store.
That's the issue, all calipers around the vehicle are "New" since a year ago. And they're both having the same wear issues? I took a little piece of aluminum from a pop can and placed it between the pad and rotor and had someone pump the brakes. It bit down but after they released the brake it was still holding pressure on both sides. I can manually return them by applying pressure, but there is what feels like fluid resistance. I can't be so sure it's an issue with the caliper when it's both the rears exhibiting the same issue. But not an issue with the fronts.
 

Mektek

Member
May 2, 2017
656
FL
Perhaps there could be a defect with the rebuilt rears? When I first rebuilt the fronts I had sticking pistons. I had to also replace the pistons and then all was well. Normally I don't need to replace pistons so this surprised me.
 

budwich

Member
Jun 16, 2013
2,027
kanata
did you bleed the brakes and if so, was there any "stuff" in the fluid coming out of the rears that would indicate contamination in the lines. Further, your test with the aluminum can is a good idea and as it indicates an issue with the piston "return". How did you "manually" return the piston / cup?
 
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Mooseman

Moderator
Dec 4, 2011
25,257
Ottawa, ON
That's the issue, all calipers around the vehicle are "New" since a year ago.
What do you mean by "New"? Are they rebuilts or brand new ones? What was the reason for replacing all of them?
 

gmcman

Member
Dec 12, 2011
4,656
There's a chance the rubber brake hoses have started to deteriorate, in which case they tend to collapse on the inside. This will cause the fluid to not easily flow back when the brake pedal is released.

Keep in mind, if all else fails, and you do replace the brake hoses, the metal lines that thread into the brake hose mounting block have a coating on them and tend to stick to the flare nut.

To avoid twisting the steel line causing a major headache, I have needed to heat the flared nut/steel line junction with propane for about 10 seconds to melt the coating. Applying pressure from a line wrench while heating until it just starts to give.

One other thing comes to mind...

Do you drive the Envoy or someone else? Does the driver use 2 feet while driving and rest their left foot on the brake pedal? This happens more than you think.
 

Barbatio

Original poster
Member
Jun 8, 2021
5
Ohio
What do you mean by "New"? Are they rebuilts or brand new ones? What was the reason for replacing all of them?
I will get back to you on this, they are supposed to be brand new parts, they were replaced because 2 of the 4 were locked up, one in front, and one in back.
 

Barbatio

Original poster
Member
Jun 8, 2021
5
Ohio
There's a chance the rubber brake hoses have started to deteriorate, in which case they tend to collapse on the inside. This will cause the fluid to not easily flow back when the brake pedal is released.

Keep in mind, if all else fails, and you do replace the brake hoses, the metal lines that thread into the brake hose mounting block have a coating on them and tend to stick to the flare nut.

To avoid twisting the steel line causing a major headache, I have needed to heat the flared nut/steel line junction with propane for about 10 seconds to melt the coating. Applying pressure from a line wrench while heating until it just starts to give.

One other thing comes to mind...

Do you drive the Envoy or someone else? Does the driver use 2 feet while driving and rest their left foot on the brake pedal? This happens more than you think.
I'm leaning towards lines as well. I'm really the only person who drives this vehicle, it's rare that someone else drives it.
 

TollKeeper

Supporting Donor
Member
Dec 3, 2011
8,047
Brighton, CO
I have the same problem as the OP on one brake caliper on the XUV.. Had not even considered the brake hose.. Might have to do that. Still on factory calipers all the way around.
 

budwich

Member
Jun 16, 2013
2,027
kanata
In the distant past and different vehicle, the hose can be a significant issue. In that vehicle, even with a c-clamp AND a new caliper, you could barely force the piston back after it was actuated which was the original problem. A new caliper did nothing to help resolve the issue. Only replacing the hose, was the brake back to normal release.
 

gmcman

Member
Dec 12, 2011
4,656
For those attempting to replace the brake hoses.....please.....take your time, if the steel line is trying to turn with the nut...STOP what you are doing and apply some heat to the junction. This will melt the outer coating of the line and allow the nut to turn freely.

When attempting to loosen the nut, leave the 10MM bolt that secures the junction block attached to the vehicle. You can remove that bolt after you get the flare nut loose.

Take a line wrench and just break the nut free, don't try to turn it after you break it free. Then apply the heat while applying slight pressure to the wrench, when the coating softens up, the nut will turn easily and not twist the line.

You don't want to twist the steel line as many are NLA and you will need to bend and flare a straight section of tubing.

A little heat where the line enters the flare nut is all you need, takes about 10 seconds.
 
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mrrsm

Lifetime VIP Donor
Supporting Donor
Member
Oct 22, 2015
7,639
Tampa Bay Area
And to Dial In on your issue about the lack of movement with the Brake Pads inside of the Rear Brake Brackets... Check out Eric 'O''s Video from The South Main Auto Channel covering what he does to PREVENT this phenomena of "Rust Jacking".

He Un-Boxes and disassembles a Brand New Rear Brake Assembly to show precisely where to apply the Pematex "Purple Jesus" Silicone Brake Grease in places that ordinarily get missed for the Grease. You can catch this segment at 55:17 into the lengthy view of Part 1 of 2 Parts:


Also... he covers the same issue of "Rust Jacking" even more dramatically for the GM Truck Front Brake Assemblies in this video at around 20 Minutes into the view:


These Videos are all worth downloading and watching again and again because he covers the Complete Work involving Front Wheel Hubs, Front and Rear Brakes just about as universally Good as it can Get.
 
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Chickenhawk

Member
Dec 6, 2011
779
Interesting videos. He lubes under the hardware but does not lube the pad ears. He makes a very good point about rust getting under the hardware and squeezing the pad ears. I know I just did my brakes yesterday, and one pad in the back was angled and worn to metal. I know I lubed the pads when I put them on five years ago, but rust had really jammed one side.

I wish I saw this video yesterday! I cleaned the bracket with a good wire brush of course before I put on the hardware but only put lube on the pads and not under the hardware. I don't think that is critical enough for me to take them apart and do them again though. Besides, if I get another five years out of my rear pads, that is good for me. (I do about 12,000 KM a year.)

I used Raybestos Element 3 pads on the front and Bosch QuietCast pads on the rear. I also used AC Delco Advantage Coated rotors. I usually go higher end on the rotors (NAPA Premium or AC Delco Professional) but again if I can get five years out of my brakes, I will be happy. Especially at half the price.
 
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mrrsm

Lifetime VIP Donor
Supporting Donor
Member
Oct 22, 2015
7,639
Tampa Bay Area
Universally, all of the Mild Steel Ears on Brake Pads are meant to glide freely within all of the nested Stainless Steel Bracket Inserts. Applying any Lube on the S/S surfaces just allows for yet another place to collect and hold Road Grime, Moisture and Road Salt in Winter. Eliminating the "Bracket Swell" makes perfect sense after watching Eric "O" 's great "Before and After" F&R Brake Repairs. Somebody should "Gift" Eric with a Very Thin, Flat Box-End Wrench that can slip in between the Boot Rubber and the Bracket and firmly hold those Inner Guide Pins while he tightens down the two outer Pin Fasteners.
 
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