Random Front Caliper Sticking

[Rovert]

Hey guys,

A couple of times I have felt the brake pad riding the rotor because when I come to a stop I hear that slight squeak as the rotor stops against pad. On slight inclines the car would no roll in neutral. I was on the highway at around 70mph and I noticed the sound of a rumble and steering wheel shaking (more when steering angle biased to left) so I pulled off to drive slowly as the rotor cooled off and drove city streets to my destination which brought normal feeling back. At my destination there was a ton of heat from the front driver side (enough to burn fingers) while the other corners were next to warm/cool.

On the way home after full cooling the brakes didn't appear to stick. I would roll on any slight incline/decline in neutral. When I got home the rotor was still hotter than the other corners.

This seems to be a random degree of sticking. I just bought the car and it has about 54,000 miles on it now. I have the previous owner's records that the brakes were changed at 44,000 miles in October 2011. I'm not sure when the brake fluid was changed out but the PPI said that it was dirty and needs to be changed. That brings me to what could be the problem:

1. Dirty/contaminated brake fluid with water in the lines
2. Failed seal at such a low mileage? (will inspect tomorrow)

Could it be as easy as contaminated brake fluid since the brakes randomly return to near normal operation? Can calipers show sign of failure in such little mileage or is it all about time? The car was driven in Vancouver which is known as Raincouver. LOL But I still don't see such an expensive car rusting away so early in it's mileage. I guess the main reason I made this post is to ask: What can I look out for and test to determine the issue with this caliper?

[brettbimmer]

Hey Trevor,

Congrats on the new ride! She looks beautiful.

I just had a brake caliper sticking as you described above on my E36 daily driver. Ended up replacing both front calipers with rebuilt units as a preventative measure while I was doing one side due to age and mileage on the car, since the one side was really sticking badly. Brakes on that car are single-piston calipers, and from what I gathered the piston must've had some rust on it which was binding and not allowing the pads to float back free from the rotor. FWIW, my car has been in the family since new and has always had brake fluid changes annually. I suspect that the case with your M3 may be the same - brake pistons sticking and not allowing the pad to properly release, probably due to some rust on the piston which may be caused from a combination of a lack of use and infrequent fluid changes. You could certainly try a full brake fluid swap, but at this point I doubt that it will cure the sticking caliper problem. I actually asked my mechanic about this issue and he said just buy remanufactured calipers rather then trying to rebuild them yourself. Hope that this helps. Let me know if I can answer more questions.

EDIT: Brake fluid is hygroscopic, meaning that it absorbs moisture from the air, so that is why the track guys want to see fluid changes every 6-12 months as the water lowers the boiling point of your brake fluid.

[LivesNearCostco]

I can think of 2 causes for sticky caliper: rusty piston (as Brett said) or dirty/rusty caliper pins. The caliper pins are easy to check. Remove wheel, remove hold-down clip, then remove both pins. Remove caliper and hang with wire/bungy or sit on top of rotor. Check if pins are rusty and if slide smoothly in rubber bushings. If rusty, clean up with Scotch brite or steel wool. If rubber bushings are buggered or pins very rusty, buy new ones (pulling out old ones is a little bit of hassle). If pins and bushings okay, then it's your caliper piston.

I rebuilt my rear calipers recently. It's not hard IF you are comfortable with...
1) Disconnecting your calipers
2) Getting brake fluid all over the place (I worked in an oil drain pan)
3) Have compressed air to pop out the piston (I used a $30 HF tire inflator with plastic accessory tip on the hose)
4) Have way to plug or clamp the brake line so you don't loose too much fluid while you do it.
5) Ready to bleed brakes up to 2x afterward (bleed, drive around, bleed again).

Of course if you replace calipers, you have to do #1 and #5 anyway. The hardest part was getting the new piston dust boots sweated properly. There's a whole thread on Bimmerforums.com about how do do that. I removed my brake lines because I was replacing them, so I couldn't clamp the hard line. Couldn't get foam earplug into the hard line and didn't have any golf tees. I whittled down a chopstick and jammed it in there but didn't fit well so brake fluid kept dripping out the whole time I was rebuilding the caliper. Lesson: buy some golf tees! Oh and a hook and pick set to remove old piston seal.

Edit: If not changing brake lines, you can clamp the flex line and after removing calipers, unscrew caliper from flex brake line.

If sounds like too much bother, go for the rebuilt calipers!

[derbo]

I agree with both of you guys. I would definitely check the guide pins first since they are far cheaper to replace than caliper units.

[Stewbie]

3) Have compressed air to pop out the piston (I used a $30 HF tire inflator with plastic accessory tip on the hose)


Place a wood block in the caliper to catch the piston. Keep your fingers out of the way.

I have an air compressor if you don't.

[Rovert]

So it looks like the previous owner never did a brake flush. I wonder if it's maintenance period included a flush. This was the colour of the fluid:

http://img.tapatalk.com/d/14/05/22/aqusety2.jpg

http://img.tapatalk.com/d/14/05/22/be5e8a2u.jpg

So I made sure I bled all the brakes starting from the furthest away from the brake reservoir.

When I got to the problem corner I pulled the guide pin out (7mm hex bolt needed) and it slid put nicely. But trying to release the piston's grip too an extraordinary amount of leverage to even press it in a bit. Looking at the piston already looked a bit scary after it came loose:

http://img.tapatalk.com/d/14/05/22/hapajyju.jpg

I pumped the brake pedal a little to start ejecting the piston a bit and I pulled the seal and saw this:

http://img.tapatalk.com/d/14/05/22/evetebe5.jpg

I'm glad it's been caught before failure. Is getting a front pair of rebuilt calipers for $75 approx, the best way? I have a hunch if I try the rebuild DIY method, the caliper cylinder wall will be scored and damaged beyond repair.

I live in Canada. If there are any quick ways of getting stuff in Canada (better immediately from local supplier) for a bit more money that would be great. Other than that I have another vehicle to zip down to my USA post office box, 30 minutes drive away. Any advice guys?

[Stewbie]

Alexandre has had good luck with eeuroparts.com. apparently they are more Cdn friendly than the other shops.

Sent from my Galaxy Nexus using Tapatalk

[slater]

Alexandre has had good luck with eeuroparts.com. apparently they are more Cdn friendly than the other shops.

Sent from my Galaxy Nexus using Tapatalk

they are, indeed. i had a good experience as well.

peter

[danewilson77]

Trevor, how did that caliper piston compare to the others?

The friendliest forum on the planet.

[LivesNearCostco]

Nice work. Fluid looks bad. Be careful pumping brake with no pads in there, can accidentally pop cylinder out of caliper, or crush a finger. If you rebuild, you can probably clean up piston sufficiently with scotch-brite/steel wool, or you might need new pistons. The inside of the caliper bore cylinder should be cleaned too but is not as critical since the piston rides against the inner seal, not directly the inner wall of the caliper bore.

If it were mine and i could get rebuilt calipers for $75 a corner (USD or Canadian), I would get rebuilt calipers. Rebuild kit costs $6 for generic version and $30 for Ate (per corner) but does not include new cylinder--it's just one new seal and one new dust boot. BTW, what you pulled back was the dust boot. And reinstalling that was the hardest part of my caliper rebuild!


So it looks like the previous owner never did a brake flush. I wonder if it's maintenance period included a flush. This was the colour of the fluid:
I pumped the brake pedal a little to start ejecting the piston a bit and I pulled the seal and saw this:

http://img.tapatalk.com/d/14/05/22/evetebe5.jpg

[derbo]

That fluid definitely looks terrible! I would get rebuilt calipers as well. At that cost, it seems like a waste of time to rebuild unless you want to learn.Also make sure the rebuilt calipers have been painted or they will exhibit surface rust. I had previous experiences with rebuilt calipers that were not repainted before sold. These were non-bmw calipers but double check non-the-less.


This looks like it will solve your sticky brake caliper!

[Rovert]

So I decided to take it apart just to learn. This is what I found:

http://img.tapatalk.com/d/14/05/23/abu9u7eg.jpg

Lots of rust under the boot. So I took the piston out and sanded it down until it was smooth without pulling off a layer of steel. This should get me by for a while until I get rebuilt calipers and paint them.

http://img.tapatalk.com/d/14/05/23/3y2eva2e.jpg

The inside cylinder wall was perfect. No rust or scoring. I'm getting a rebuild kit to install now and the car should be good to go.

http://img.tapatalk.com/d/14/05/23/e6yhyhag.jpg

[derbo]

Glad it worked out Trevor!

[E_Rak]

HOT TIP: If AutoZone carries the right calipers for the M, go that route. They are re-manufactured OE units with BMW stamps, and carry a lifetime warranty.

[Rovert]

I wish I lived in the USA near an autozone. LOL. There's no such thing in Canada. I rebuilt my caliper and the caliper releases as it should. All good!!

[LivesNearCostco]

Great job! You might not even need the rebuilt caliper now. When I did mine--and replaced the brake hoses--the brake pedal was a little mushy after one bleeding. Drove around a few days and bled again, then it felt right. I think some air was trapped in the caliper or new brake hoses.

[derbo]

I'm glad it worked out Trevor!

[Rovert]

Nice work. Fluid looks bad. Be careful pumping brake with no pads in there, can accidentally pop cylinder out of caliper, or crush a finger.

BTW, what you pulled back was the dust boot. And reinstalling that was the hardest part of my caliper rebuild!

I pumped it very slowly just to make it move 1/2 inch. My friend was guiding me as I did it. When we actually got the piston out I pumped the pedal more times at a slow pace until the pedal went hard and wouldn't go any further. The easiest way to get it out after that point was undo the caliper from the brake line and use a large flathead against the seal edge and bang lightly with a hammer around the whole piston until it popped right out nicely.

Putting the piston back into the caliper I had to do the same. It didn't go in like butter like on some Youtube videos. I seated the piston and wiggled it back and forth until it slipped over the new seal. Then I too a 2x4 against the piston and gently tapped it with a hammer until it slipped in flat. After that I took a small flat head to tuck in the seal to seat it around the inner cylinder wall. After re-attaching the brake line and installing the caliper back on the carrier, the caliper bled itself out the top as it slowly filled up with the gravity fed brake fluid. I drove it over 10 miles in the city and all is good. Back to normal for now until the next project...