Seizing caliper?

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OVERKILL

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On the M5.

I developed a "squeek squeek squeek" from the right front wheel that goes away the instant you touch the brake pedal.

Brake pads are relatively new and have PLENTY of meat on them.

Rotors are OE and were machined.

There appears to be a little bit of a thickness variation in the rotor (can't feel it in the pedal) because with this wheel off the ground:

A). It doesn't "spin" freely. You can rotate it, but it doesn't continue to spin.

B). If you spin it fast enough you can reproduce the squeek.

C). There's a small "easy" spot when rotating it where it spins easier, but then goes back to the way it was.

Yesterday I pulled the wheel looking for the source of the noise. It seemed to come from the caliper/pad/rotor interface.

I removed the caliper.

I was able to then "spin" the rotor with very little effort and it kept spinning with no funny feel to it at all. So the wheel bearing is fine.

I took a file to all the sliding surfaces, pulled the pins, cleaned them, lubed everything with Permatex synthetic brake lube and reassembled.

Problem is still there. It is like the caliper is putting just a bit of pressure on the pad and it shouldn't be. The calipers are original, and while not "high mileage", they are old. I'm not sure if the original owner ever had the brake fluid changed either. Most likely not.

I'm thinking the caliper is on its way out.

Thoughts?
 
Originally Posted By: OVERKILL


Rotors are OE and were machined.



How long ago were the rotors machined?
How long after the machining did the noise begin?
 
In a lot of caliper design, the seal on the piston is designed to slightly retract the piston when the hydraulic pressure is relieved.

Perhaps in your case, there's slight corrosion in the bore, just enough to prevent the piston from retracting. Are you able to rebuild the caliper yourself?
 
You will obtain substantial and critical information by closely comparing BOTH sides to each other.

1) Raise the entire front end so BOTH wheels are off the ground at the same time (use center jacking point).
2) Remove BOTH front wheels.
3) Remove BOTH front calipers (and hang them from the springs so there is no strain on the hoses).
4) Remove and compare BOTH sets of brake pads. Compare like to like, i. e.: trail edge of left outer pad to trail edge of right outer pad, etc.

Are both sides EXACTLY identical, or are there differences? If there are differences, describe.

Is there sufficient piston standing proud of the caliper that you can peel back the dust boot and check for rust or gum on the piston?

Can you get a set of Channel-Loks onto the piston lip and rotate the piston within the caliper? If the pistons will rotate, does one rotate more easily than the other?

(There is one more test that is very effective in diagnosis, but if you are unsure of the date of last brake-fluid change, I will not suggest it.)
 
How are the pads looking, are the wearing evenly?
My focus had the same thing happen and pads were not wearing evenly and the pad material was not parallel to the backing plate. However the rotoras were also very rusty and you could see that the pads did not make full contact with them.
In any case, new pads and rotors fixed the issue.
 
Originally Posted By: chrome
In a lot of caliper design, the seal on the piston is designed to slightly retract the piston when the hydraulic pressure is relieved.

Perhaps in your case, there's slight corrosion in the bore, just enough to prevent the piston from retracting. Are you able to rebuild the caliper yourself?


I don't know if I can get new parts for it if I did. I'll probably just buy new ones from BMW if that's the case.
 
Originally Posted By: Christopher Hussey
Originally Posted By: OVERKILL


Rotors are OE and were machined.



How long ago were the rotors machined?
How long after the machining did the noise begin?


They were machined about 6 months ago easily, if not longer than that. The squeaking started the other day.
 
Originally Posted By: Tegger
You will obtain substantial and critical information by closely comparing BOTH sides to each other.

1) Raise the entire front end so BOTH wheels are off the ground at the same time (use center jacking point).
2) Remove BOTH front wheels.
3) Remove BOTH front calipers (and hang them from the springs so there is no strain on the hoses).
4) Remove and compare BOTH sets of brake pads. Compare like to like, i. e.: trail edge of left outer pad to trail edge of right outer pad, etc.

Are both sides EXACTLY identical, or are there differences? If there are differences, describe.

Is there sufficient piston standing proud of the caliper that you can peel back the dust boot and check for rust or gum on the piston?

Can you get a set of Channel-Loks onto the piston lip and rotate the piston within the caliper? If the pistons will rotate, does one rotate more easily than the other?

(There is one more test that is very effective in diagnosis, but if you are unsure of the date of last brake-fluid change, I will not suggest it.)


Great advice, and thank you. I don't think I'll have time for that in the next few days however, as I have a VERY busy month coming up unfortunately
frown.gif


The car doesn't have a front central jacking point, so I'll have to jack up both sides and put the front on stands.
 
Originally Posted By: KrisZ
How are the pads looking, are the wearing evenly?
My focus had the same thing happen and pads were not wearing evenly and the pad material was not parallel to the backing plate. However the rotoras were also very rusty and you could see that the pads did not make full contact with them.
In any case, new pads and rotors fixed the issue.


The pads and rotors look excellent and there isn't really any rust build-up either
21.gif


I'm thinking the caliper is hanging the piston out a bit causing the pad to "scuff" the rotor as it spins. Which would explain the resistance.
 
Given the cost of new calipers from BMW, it will be well worth the effort to troubleshoot this problem. Good advice from Tegger et al.

Also, might be worth taking off the disc and cleaning both mating surfaces (hub/disc) with a wire brush. If corrosion sets in between the surfaces, that will lead to symptoms similar to DTV.
 
Originally Posted By: chrome
Given the cost of new calipers from BMW, it will be well worth the effort to troubleshoot this problem. Good advice from Tegger et al.

Also, might be worth taking off the disc and cleaning both mating surfaces (hub/disc) with a wire brush. If corrosion sets in between the surfaces, that will lead to symptoms similar to DTV.


The mating surfaces are spotless (should have mentioned that in the OP, my apologies) and have already been cleaned recently.

Yes, the calipers are about $500/each..........
crazy2.gif
 
In addition to the caliper checks above, it is possible that the brake hose itself has started to degrade internally, preventing free fluid flow when the piston should retract...in essence, acting like a one way valve...if the calipers check out, then I suggest changing front brake hoses and flushing the fluid...
 
I agree with Astro. I have seen the hoses cause a similar issue. Even if you replace the caliper I would also replace the hose if it's a high mileage vehicle.
 
If you drive it around the block easy a few times, is there a difference in temperature of the rotors after you park it?

I assume this is a special car that doesn't get driven daily. Find a safe place and give the brakes a bit of a workout and see if that helps.

I rebuilt a front caliper that had been dragging on an e28 535i recently. It was just cleaning the piston and bore, and replacing the seal and boot. The brakes had been bled recently but there was still a lot of gunk down in the caliper. I thought it would be difficult and was kind of timid about it but once you take it all apart its actually pretty simple. Watch some videos on how its done.

I would get a rebuild kit from BMW or from the caliper builder and give it a shot.
 
when do you hear the squeak? low speed, high speed, affected by turning? do you hear it when applying parking brake instead of regular brake? check that the pads are worn evenly and the caliper and pads slide freely. the flex hose could be blocked inside as well. does that have tapered rotors? that has lug bolts instead of studs right? you might want to tighten a few on the rotor to ensure that it is flat on the hub when rotating the wheel.
 
Originally Posted By: cb_13
I agree with Astro. I have seen the hoses cause a similar issue. Even if you replace the caliper I would also replace the hose if it's a high mileage vehicle.


It isn't a high mileage vehicle.
 
Originally Posted By: JamesBond
If you drive it around the block easy a few times, is there a difference in temperature of the rotors after you park it?

I assume this is a special car that doesn't get driven daily. Find a safe place and give the brakes a bit of a workout and see if that helps.

I rebuilt a front caliper that had been dragging on an e28 535i recently. It was just cleaning the piston and bore, and replacing the seal and boot. The brakes had been bled recently but there was still a lot of gunk down in the caliper. I thought it would be difficult and was kind of timid about it but once you take it all apart its actually pretty simple. Watch some videos on how its done.

I would get a rebuild kit from BMW or from the caliper builder and give it a shot.


It is daily driven, I put a lot of miles on it actually.

I was unaware that BMW sold caliper rebuilt kits! If they do, then we are good to go. I've done calipers before, just didn't think BMW sold the necessary parts.
 
Originally Posted By: outdoorsman310
when do you hear the squeak? low speed, high speed, affected by turning? do you hear it when applying parking brake instead of regular brake? check that the pads are worn evenly and the caliper and pads slide freely. the flex hose could be blocked inside as well. does that have tapered rotors? that has lug bolts instead of studs right? you might want to tighten a few on the rotor to ensure that it is flat on the hub when rotating the wheel.


- The squeak is constant, and happens at any speed.

- It is not affected by turning.

- The parking brake does nothing to it, as it is in the right front wheel

- The flex hoses LOOK in good shape, no signs of dry rot, but I guess this is a possibility

- No, the car does not have tapered rotors

- Yes, it has lug bolts. But also has bolts that hold the rotor to the hub
 
is the backing plate contacting the rotor? pad shims could be falling off too. if you cant push the piston back easily but it pushes back easily when the bleeder is opened that would indicate a restriction in the line.
 
Originally Posted By: outdoorsman310
is the backing plate contacting the rotor? pad shims could be falling off too. if you cant push the piston back easily but it pushes back easily when the bleeder is opened that would indicate a restriction in the line.


No, nothing is contacting the rotors. Pad shims are perfect, I had the works apart yesterday as per my OP.

I'm hesitant to crack the bleeders on these as I'm worried about breaking them.....
 
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