HELP!!! Best test for stuck caliper?

[we350z]

My brakes were working just fine prior to me changing the pads and rotors. I have maybe 150mi on the new pads and rotors. Shortly after I noticed the wheel jerks to the right when I brake reasonably hard. Everything seems even and fine when I apply the brakes lightly.

I think I have stuck caliper but want to be absolutely sure, some are saying it could be thrust arm / tension strut / front control arm bushing or ball joint. I have already done the basic stuff: re-checking that all the hardware is torqued properly, rotors are straight and true, no pad material visible on rotors, inboard & outboard pads are sitting flush on the rotors, brake lines not kinked.

I would like to prove this out with a high degree of certainty before buying a replacement reman caliper and swapping it out. I am reading bad things about bleeding the brake system. These are all methods I have heard for determining stuck caliper - trying to determine what is the best:

Driving tests:

1) Temperature - compare by putting hand near each rotor on each side to see if one is hotter then the other. Perhaps use thermometer to be more scientific.

2) Rotor blueing - may occur on the rotor that is compensating for the other side with the seized caliper.

3) Dust - Clean wheels, more brake dust should accumulate on the good side.

4) Smell - stronger caliper is working harder may overheat and smell asbestos from brake pads

5) Steering wheel jerk/shudder/vibration (mine jerks to the right quickly upon hard braking then stops) - wheel should move to the stronger side and vehicle will also veer in this direction.

6) Measure rotor thickness with digial caliper and compare each rotor thickness (prob too close with low mileage). Try measuring at different points on rotor to see if even.

Other Tests:

QUESTION - can the piston seize in any position? Is it usually compressed (open or pads spread wider) or uncomressed (closed or pads spread narrower)????

7) Jack up front end - apply brakes to build up pressure then release and rotate each wheel.

QUESTION - Is it also worth trying to do this while keeping the pressure applied to the brake pedal? Either with a buddy putting his foot on it or with a brick or something?

8) Remove wheels and use c-clamp to compress the calipers. A seized caliper should not move from its stuck position. Also then apply pressure to brake pedal and see if they uncompress.

Lastly - being that i have only 150mi on the new rotors, is it likely they will be OK once i replace seized caliper or will I need to machine or replace the fronts (or possibly just the pass side if it warped?) I can't imagine they would be toast with such low mileage.

Any other suggestions? Thanks guys!!!!!

[Tomaz]

All of the symptoms you list for finding a stuck caliper are valid. To your question about which position a caliper would stick, usually they stick compressed (contacting the pad) and fail to retract. Test 7 should indicate if a caliper is sticking. Another thought, the caliper on the left may have an air bubble causing it not to compress properly, making the caliper on the right do all of the work. Good luck

[we350z]

How can I get an air bubble without opening the system?

Cool - it seemed like almost everyone I read about having this problem the caliper compressed where the pad is contacting the rotor. So it seems to me like that should cause that brake to be applied until the pad/rotor wears away enough. This is why most say they can smell the asbestos from the pads.

I wanted to correct myself in my question below #7. Applying the breaks while turning the wheel would not help because the good break would hold and you would not be able to turn the wheel on the other side. You could, however perhaps remove the caliper on the assumed good side and do this test.

Well looks like I won't have time to mess with this until the weekend. Anyway i should be able to figure out what's what.

Originally Posted by Tomaz

All of the symptoms you list for finding a stuck caliper are valid. To your question about which position a caliper would stick, usually they stick compressed (contacting the pad) and fail to retract. Test 7 should indicate if a caliper is sticking. Another thought, the caliper on the left may have an air bubble causing it not to compress properly, making the caliper on the right do all of the work. Good luck

[Tomaz]

Originally Posted by we350z

How can I get an air bubble without opening the system?

You need to bleed the brakes.

[we350z]

Am i missing something? Is bleeding the brake system part of a standard brake job? It was not suggested in the DIY. Is this what BMW mechanics do? It's worth a try I guess. I am a little confused here... please explain. Does compressing the piston with the c-clamp introduce air bubbles? How did I get air bubbles!!!! Is this why the DIY suggested optiional step of opening the Master Cylinder Brake Resovier cap?!!!

Step 1:Loosen the Master Cylinder Brake Resoivor Cap*** I find his step is optional and do not do this myself ***Proper procedure does call for loosing this cap when you compress the calipers back as fluid is pushed back inot the master cylinder. I've done this hundreds of times without loosening the cap with no ill-effects. You can do either. When in doubt, play it safe.

Open the hood and loosen the Master Cylinder Brake Resevoir Cap. Do not remove it, just loosen it all the way.

The Master Cylinder Brake Resovier cap is located on the driver side at the back of the engine on the firewall. Its a semi-transparent canister showing the level of brake fluid in it.

I am just a little hesitant because I am reading horror stories about brake bleeding on the X5. Also I read somewhere that you need some sort of computer to do this to cycle the ABS unit but maybe that was just if you get air in the abs valve. I guess for normal bleeding air cannot enter the nipple on the caliper and you never let the fluid level go below the minimum level so any air bubbles are just pushed out?

Any tips or links to procedures for this? I really don't want to f it up worse Is this something I should not attempt myself and just take it to an indy mechanic?

Someone please set the record straight on bleeding and if it is needed in my situation...

Originally Posted by Tomaz

You need to bleed the brakes.

[JCL]

You should take it to a shop and let them fix it. Tell them what you have done so far, and let them take it from there.

Whereas your brakes may benefit from bleeding, you should not do it IMO.

[we350z]

I should not do it because it's a bitch on this car or i am not qualified or what? I need to do it on my Z since I am installing a BBK, no one seems to mention anything about it being difficult to do on that vehicle? Aren't they all the same!!!

Originally Posted by JCL

You should take it to a shop and let them fix it. Tell them what you have done so far, and let them take it from there.

Whereas your brakes may benefit from bleeding, you should not do it IMO.

[Meiac09]

1) Start Car
2) Enter Freeway
3) Drive for a bit
If its smoking and shuddering, its hung. If not, its fine
JK, don't do this. It happened to me once, I think that if you really had a stuck caliper, you'd really know it.

[we350z]

Yea - I agree with you and the vehicle is NOT exhibiting smoking/shuddering behavour. IN FACT steering wheel is perfectly straight and normal and ride is smoothe. No noise coming from brakes, no burning smell, no smoking. WTF. Not sure how likely a candidate for seizure a caliper with 69Kmi is on it either.

I agree with you 100% that I would really know i have a stuck caliper too lol. This still doesn't explain why the hell my steering wheel jerks to the right upon applying a decent amount of brake pressure.

Enough speculation. I will do the damn tests. It may very well be the stupid bushings. UGH!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!

Originally Posted by Meiac09

1) Start Car
2) Enter Freeway
3) Drive for a bit
If its smoking and shuddering, its hung. If not, its fine
JK, don't do this. It happened to me once, I think that if you really had a stuck caliper, you'd really know it.

[JCL]

My suggestion to take it to a shop was based on your diagnostic skills (no slam, just noticing) and the fact that brakes are a safety item. Bleeding brakes is fairly straightforward, but not if you haven't done it before. Yes, you can get air in the bleed nipple, just let the pedal rise while the bleeder is open. The X5 has some complexity to the brake system due to the ABS module, which can trap and hold air bubbles. Thus, all cars are not the same. If you get air in the system, and it gets into the ABS module, you may not be able to repair it without taking it to a shop that has a BMW computer to cycle the ABS controller. $$$$.

Your other question was about a vehicle with low miles having a stuck caliper. The failure of a caliper isn't related to miles, it is related to time, and more specifically, not changing the brake fluid every two years. That lets water collect in the system, it goes to the low point (the caliper), and corrodes around the piston. When you push the piston back while changing pads, the piston can can hang up on the corroded area.

All that said, I don't think you have a caliper problem, I think you have a suspension problem. That is because of the problem description, but it is just a judgement call without more info.