[TheMidnightNarwhal]

I've determined that my rear driver side caliper is sticking. And also confirmed that it seems to be the caliper itself and not because of a hose.

My question is, does a caliper rebuild kit with the rubber boot and square cut seal is all I need to fix the sticky caliper? The reason my calliper sticks is because the square cut seal is torn or something correct? But then wouldn't I have fluid leaking.

Also, is it worth to rebuild it or should I just get a new one?

[Cloverdale]

The sticky and seized calipers I've encountered did not leak. You can familiarize yourself with caliper rebuild procedures on Youtube. You're going to have to bleed the system once the caliper is removed. Determine that the caliper bleed screw is removable before you rebuild it, otherwise all your caliper rebuild work will have been for not.

[lobotomy]

The drivers rear caliper on my 2011 328ix seized as well. I was surprised because I am methodical about flushing fluid from all 4's every 2 years to remove contaminants from system. I was not able to determine if it was the caliper or the line, so I bought both. I opted for a new OE replacement in lieu of rebuilding. I ended up leaving the line alone as it was giving me trouble at the fitting, and I was using the proper line wrenches to seperate! Turned out to be the caliper. I opted to not to rebuild the caliper because I did not want to tie up the vehicle if I ran into any caliper issues, like a pitted piston, corroded bore, etc. To me, a fast caliper R&R to save time was worth the cost over rebuilding. Like Clover mentioned, be sure bleeder screw is OK. I flush all old fluid before installing a new or rebuilt caliper. I like having fresh fluid in the system when doing final bleeding after installation.

[TheMidnightNarwhal]

Okay thanks I hope the rebuild kit works. Just need to find a place locally that has them. I saw a few videos I'm just surprised all of this is because of a seal ha. If the rebuild doesn't work I'll check for a caliper.

Bleeder works, I opened it part of my troubleshooting to see if it unseized but it didn't so I believe the seal is the issue.

[eljay]

Have you actually confirmed that it is the piston that is seized/sticking?
The common reason for a stucky/seized caliper is the slide pin that hasn't been lubricated properly or the rubber boot on the pin that is torn.
Start there and confirm the caliper is moving easily back after braking force is released.

[TheMidnightNarwhal]

Originally Posted by eljay

Have you actually confirmed that it is the piston that is seized/sticking?
The common reason for a stucky/seized caliper is the slide pin that hasn't been lubricated properly or the rubber boot on the pin that is torn.
Start there and confirm the caliper is moving easily back after braking force is released.

Yeah I took it all apart and cleaned it up and greased, and the first moment I hit the brakes to pump them, it seizes up and wheel doesn't spin as freely as it should.

Also, the BMW manual actually says to not grease the pins and I've done so before no issues on other BMW. That said, I greased it this time to rule that out and still seized once brakes are applied. I am able to push the piston in though with a tool smoothly so it has to be the square cut seal not doing it's thing right?

[TheMidnightNarwhal]

I ordered a rear rebuild kit from Rock Auto, couldn't find any place local to me that had one...

Not sure what the little nub in the kit is for, looks like a bleeder screw cover maybe? But yeah watched videos and seems easy enough. Just hope the piston is mostly fine.

[eljay]

If those seals are compromised, you would see fluid leak, which you didn't report and the piston seems to be moving freely.

Are all the gliding surfaces for the pads clean, free of rust scale and lubricated too? I would maybe change pads first.

If you are going to remove the caliper, apply brakes first to close the master cylinder and minimize fluid loss from the hose.

Yes, the little nub is the bleeder screw cover.

[TGTIW]

The Duralast brake calipers from Autozone are actually rebuilt ATE/BMW calipers, an option if you don't want to bother rebuilding them.

[TheMidnightNarwhal]

Originally Posted by eljay

If those seals are compromised, you would see fluid leak, which you didn't report and the piston seems to be moving freely.

Are all the gliding surfaces for the pads clean, free of rust scale and lubricated too? I would maybe change pads first.

If you are going to remove the caliper, apply brakes first to close the master cylinder and minimize fluid loss from the hose.

Yes, the little nub is the bleeder screw cover.

Hmm okay, seems like I'm seeing conflicting info on this. Online the culprit of a calliper not releasing seems to be because of the square cut seal. And in this thread someone mentioned they've seen bad ones that don't leak.

Yes they are all clean and free of rust. I did the rear brakes about 3 months ago so the pads are new and the disc. I really don't think I did anything wrong I've done brakes before and put everything back greased and cleaned and it still seized the first moment I hit the brakes. I've never encountered a seized calliper before.

I also had some noises coming from the left rear which I thought was the brakes themselves before doing my brakes, but it seem to corrobate with my calliper seizing now, appears that it slowly worsened until it didn't retract at all.

Thanks ok and yeah was gonna do that trick and cap the tip of the line to.

For bleeding, I only need to bleed that one corner right?

[TheMidnightNarwhal]

Originally Posted by TGTIW

The Duralast brake calipers from Autozone are actually rebuilt ATE/BMW calipers, an option if you don't want to bother rebuilding them.

Ah thanks but I'm not in the US.

[eljay]

Originally Posted by TheMidnightNarwhal

Hmm okay, seems like I'm seeing conflicting info on this. Online the culprit of a calliper not releasing seems to be because of the square cut seal. And in this thread someone mentioned they've seen bad ones that don't leak.

Yes they are all clean and free of rust. I did the rear brakes about 3 months ago so the pads are new and the disc. I really don't think I did anything wrong I've done brakes before and put everything back greased and cleaned and it still seized the first moment I hit the brakes. I've never encountered a seized calliper before.

I also had some noises coming from the left rear which I thought was the brakes themselves before doing my brakes, but it seem to corrobate with my calliper seizing now, appears that it slowly worsened until it didn't retract at all.

Thanks ok and yeah was gonna do that trick and cap the tip of the line to.

For bleeding, I only need to bleed that one corner right?

Well, I guess it is possible for that square cut seal to deteriorate and then "bunch up" or twist and cause the piston to not slide in its bore smoothly while still holding the fluid in.
It's quite easy to rebuild once you have the caliper out.

[TheMidnightNarwhal]

Originally Posted by eljay

Well, I guess it is possible for that square cut seal to deteriorate and then "bunch up" or twist and cause the piston to not slide in its bore smoothly while still holding the fluid in.
It's quite easy to rebuild once you have the caliper out.

I will report back once I'm done with the rebuild, I should get the parts friday. Caliper is ready to come out just waiting on it.

[mainbearing]

IME the old square cut seals would look pliable and fine, but the piston can still get sticky. If the caliper is in otherwise good condition definitely rebuild them. The store calipers can be coin toss sometimes.

On the 328i the outer dust boot has a metal ring molded into the rubber. therefore a large socket helps to seat the seal. not sure how the 335i calipers are tho.

Plug the hose and do not let the master cylinder drain dry. I actually would replace the rubber hose together, granted only if the flare connection can be safely disconnected.

[TheMidnightNarwhal]

Alright I just did the rebuild tonight and that was it It was more that it was rusty and crusty than the seal itself I think but yeah it works fine now. The piston wasn't in the best of shape, had little pits but it wasn't leaking, cleaned it up best I could.

[PhaceN52]

Originally Posted by TheMidnightNarwhal

Alright I just did the rebuild tonight and that was it It was more that it was rusty and crusty than the seal itself I think but yeah it works fine now. The piston wasn't in the best of shape, had little pits but it wasn't leaking, cleaned it up best I could.

Just a question, with the new square seal how difficult it was to reinsert the piston, it slid easy or you had to press it with a lot of force? is the caliper releasing now? I have the same problem, took a look at one caliper I know it's sticking before bleeding (was changing fluid) and the piston was fine, but it didn't want to go back in place, like as said the square seal was preventing it from sliding. Had to use a piston compressor tool...

[TheMidnightNarwhal]

Originally Posted by PhaceN52

Just a question, with the new square seal how difficult it was to reinsert the piston, it slid easy or you had to press it with a lot of force? is the caliper releasing now? I have the same problem, took a look at one caliper I know it's sticking before bleeding (was changing fluid) and the piston was fine, but it didn't want to go back in place, like as said the square seal was preventing it from sliding. Had to use a piston compressor tool...

Haha yeah I had a bit of trouble for that. At first I was trying to make it go in by hand only but no success at all. Thought the lip at the start of the bore was the issue so I cleaned it up super well with a brass wheel but still wouldn't go in. I resorted to using a trigger clamp to help me on the third time and that worked pretty smoothly.

I was worried it meant something wasn't right but I watched videos online and they all use some kind of tool to press it in, even with a brand new piston so I think that's just normal/fine.