Image borrowed from the fine folks at Koenigsegg for your time:

Here’s the background: I have a 2003 BMW 325xiT with 160k. I drive it every day in the salty New Hampshire winter, but in the summer I get to drive my old truck more, so it tends to sit for a few days at a time, always outside. I bought this car in 2014 and in the time I’ve owned it, I put all new rotors, pads, and calipers* on it. (*rebuilt/reman)

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Why did I replace the calipers while doing brakes? Because just like my 2001 E46 wagon I had before, the brakes get a little sticky in the winter. When it’s cold out - below 30F, worse as you get closer to 0F or colder - and step on the brakes, you get normal braking until you let off, and you don’t feel that release, the rearward weight transfer of the brakes letting go. This isn’t one particular wheel or just front/just rear, it’s the whole car. My old car did this at 200+k so when I got this one at 120k, I figured, what the hell, it does it too so while I’m doing brake work let’s just start fresh all around. I do most of this work myself anyway; brakes are easy. Right? Sort of.

The problem isn’t totally gone, but it’s better and now at least I know my calipers as as good as they can be. At least I thought so, but now recently my left rear caliper is sticking to the point that the rotor is extremely hot after a drive just about anywhere. I haven’t taken a laser thermometer to it, but you can feel the heat radiating from the wheel, and you can feel the effects when you brake hard - it doesn’t brake perfectly straight because that one wheel (well, brake) isn’t right.

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Side note - credit where credit is due: my wife drove the car after it sat for 4 days and was the one to diagnose the sticky caliper. She smelled brakes, walked around the car, and found one that was noticeably HOT. Bingo! She pretends not to care about car repair, but she’s too smart not to learn and too attentive not to notice small handling changes. She also noticed my left front tire was a bit low because she felt it in the steering. OK back to the topic at hand.

Trail Rated

These “new” calipers have been on the car for just under 2 years. The cost of OEM calipers is easily 4x the cost of a reman. part that looks absolutely like new (and is likely a cleaned up OEM part). So what gives? And what to do?

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At this point I plan to at least take the caliper apart and see what those guide pins look like, and inspect the piston for what I can see of it, anyway. Maybe clean up or even replace those guide pins, and hope that helps? There are also “rebuild kits” that don’t look like anything more than a new seal for the piston (and a retaining ring for the seal).

Finally to my questions:

  • Is it worth taking the caliper apart and trying to clean things up? Does this ever really work?
  • I believe the guide pins are “dry” installation, but what about a little anti-sieze? Or bearing grease? Would that just attract more dirt?
  • Has anyone had experience with a “caliper rebuild kit”? What would that gain, exactly, if the existing seal isn’t bad?
    like this: https://www.bavauto.com/250011
  • Am I insane for considering getting much more expensive calipers to avoid replacing them again? I can do the work, but am not very good at bleeding brakes at home by myself, even with speedbleeders. Also I’m not sure I can even GET brand-new OEM calipers for the rears, short of dropping $300 EACH at a dealer. So, slap another set of rebuilt ones on there? Seems like throwing parts at it.
  • Is anyone still reading this? If so, thank you.

I feel like replacing the one sticking caliper is just buying time until the opposite one fails, not to mention WTF these should last longer than 2 years. Also I feel like something isn’t right when my three go-to reputable online parts suppliers offer ONLY rebuilt rear calipers - by that I mean, everyone else seems to be using them, why do I have a problem? Even if I could get new ones for the rear, could it possibly be worth 4x-6x the money? I’d spend the money if it meant never touching the calipers on this car ever again. I don’t plan to sell the car anytime soon. I’d keep it forever if I could. But holy hell I could put new rebuilt ones on it every year for 6 years for the cost of one from a dealer.

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Thanks for any thoughts you might have.

image credit: autoevolution.

^^ What I wish my car looked like.