Oppo Advice: Sticky Brake Caliper(s)

"functionoverfashion" (functionoverfashion) 07/14/2017 at 11:10 • Filed to: advice

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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)

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.

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?

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?
!!!error: Indecipherable SUB-paragraph formatting!!!

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.

Thanks for any thoughts you might have.

image credit: autoevolution.

^^ What I wish my car looked like.

crowmolly > functionoverfashion 07/14/2017 at 11:15

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I believe the guide pins are “dry” installation, but what about a little anti-sieze? Or bearing grease?

You sure you don’t need some of this?

Averyrm - GTI YUP > functionoverfashion 07/14/2017 at 11:16

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Typically grease is put on the guide pins, but BMW has different ideas. I lube them lightly, and haven’t had problems. Perhaps look at a dry lube for it?

https://www.wd40specialist.com/products/dry-lube/

Also double check the parking brake, sometimes those bind and give similar symptoms. The uneven braking is due to the drag and heat differential.

Rust and Dust - Oppositelock Forever > functionoverfashion 07/14/2017 at 11:18

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I’ll be a third voice to support some lube on the slider pins.

I’ll also say “kudos” to your wife! My last significant other usually got as far as “there’s something wrong, fix it” before tossing a set of keys at me.

Trevor Slattery, ACTOR > functionoverfashion 07/14/2017 at 11:26

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Most German cars have hydraulic emergency brakes that use the same caliper as the pedal. For this to work, the caliper pistons are are mounted on a threaded post. When you pull the E-brake the piston moves in and out on the threaded post separate from the hydraulic system.

Problem is, this set-up can get contaminated. I would suggest renting a master brake kit from Advance or Autozone and push the caliper piston all the way back in and see if that fixes the issue.

diplodicus > Trevor Slattery, ACTOR 07/14/2017 at 11:28

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BMW uses a drum brake inside of the rear disc for parking brake. If the pads are contacting the drum when driving it is very noticeable.

Trevor Slattery, ACTOR > Rust and Dust - Oppositelock Forever 07/14/2017 at 11:28

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Ha. I asked my wife to add some radiator fluid to my VW. VW’s have that pink stuff. Not the usual green.

It was too much for my wife. “Hey Honey...the radiator fluid. It that the pink one or the blue one?”

“DO NOT WORRY ABOUT IT!”

Rust and Dust - Oppositelock Forever > Trevor Slattery, ACTOR 07/14/2017 at 11:32

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LOL!

Obligatory (washer fluid in oil fill results):

sony1492 > functionoverfashion 07/14/2017 at 11:32

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Lubricating the guides should so it, I don’t see why they would be try when there while purpose in life is to aid movement. Also replacing the square cut seal around the brake piston(from a rebuild set) could help. That seal is what moves the piston back into place after the piston has moved outward. It also keeps brake fluid from just gushing past the piston. Removing the piston to replace the seal shouldn’t be too hard if you have the tool(sort of like a snap ring pliers) that grabs the inside of the piston so you can pull them out of the caliper.

So I’d lubricate those guides first and if the problem continues consider replacing the cup seal.

merged-5876237249235911857-hrw8uc > functionoverfashion 07/14/2017 at 11:37

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Lubrication is good on every part other than the pads and rotors. Also, make sure the pads will slide relatively freely while in the mounts. I’ve had issues with replacing brakes and the slides in the caliper bracket only to find the pads wouldn’t slide in and out without binding. If that is the case, thats likely where your problem lies. When you replace the hardware slide clips the caliper bracket must be super clean or it can lead to binding. So check for freedom of movement there before you go any further. And if they are tied up, might as well replace the pads and hardware again. You can lube the ears on the brake pads as well when you reassemble. I’ve had good luck with both the brake grease and also anti seize. But I’d start there and you might just find your problem. Also, if the brakes and hardware are new enough, you can just remove, clean and replace everything. All it costs you is time. But those mounts for the hardware clips have to be super clean. I’ve even used a cutoff wheel to square up and clean the crud out of those channels before, but that requires a steady hand.

Trevor Slattery, ACTOR > diplodicus 07/14/2017 at 11:44

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Then it has to be brake pins.

Trevor Slattery, ACTOR > Rust and Dust - Oppositelock Forever 07/14/2017 at 11:46

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Mahn...my wife would be voluntarily performing all kinds of sexual stunts to make up for THAT.

diplodicus > Trevor Slattery, ACTOR 07/14/2017 at 11:51

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Ya most likely.

functionoverfashion > Averyrm - GTI YUP 07/14/2017 at 12:25

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Yeah, I’m leaning heavily toward a little lube of some sort on those pins... and for sure the braking pull is as you said.

functionoverfashion > merged-5876237249235911857-hrw8uc 07/14/2017 at 12:27

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Thanks, I’m seeing an evening next week spent with my rear brakes, some wire brushes/wire wheels, and some lube/anti-sieze...

functionoverfashion > Rust and Dust - Oppositelock Forever 07/14/2017 at 12:32

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We couldn’t have older, high-mileage BMWs without her attention to stuff like this; she drives about 100 miles a day so she spends a lot of time thinking about things that are wrong with the car(s). Her intuition is pretty spot-on.

And yeah, I’ll be taking apart the caliper to at least spend some time before spending money, making sure things are clean and moving properly, and lubricated along moving surfaces. Plus, it gives me an excuse to spend an evening outside listening to baseball and drinking beer.

merged-5876237249235911857-hrw8uc > functionoverfashion 07/14/2017 at 13:02

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That sounds like a nice little evening. Also a small file will help to clean out the channels as well.

Sovande > functionoverfashion 07/14/2017 at 13:39

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While not a BMW, I have had caliper troubles on Volvo’s and an old Nissan 720 I have. Lubing worked for a bit on both, but the best solution for me was to replace them. Since removal and cleaning is a pain in the ass anyway, I would just replace the caliper.

BigBlock440 > functionoverfashion 07/14/2017 at 14:54

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I had a rear caliper sticking problem a few years ago, first step was replacing the caliper. Didn’t work, so I greased everything, pins, guides, everything. That didn’t work either. Tried a new proportioning valve (swapped sided with the one not sticking), still stuck. It ended up being the rubber hose. Apparently they can collapse internally and act like a one-way valve, allowing fluid to pass into the caliper but not back out. When the other side started sticking too, it was much quicker to diagnose.

brianbrannon > functionoverfashion 07/14/2017 at 15:05

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I don’t think the pins can seize if they are the rubber slider style. If you have dirty brake fluid it can corrode the caliper fairly quickly. Most likely you got a bad rebuild. I’d just replace the bad caliper and you can gravity bleed it very easily by yourself  

functionoverfashion > BigBlock440 07/14/2017 at 20:37

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Interesting. This theory makes sense for why ALL my brakes are sticky in the winter, maybe the hoses just aren’t as willing in the cold....