HELP!!! Best test for stuck caliper?

[Batm4n]

I'm having similar issues. I just did a brake job and after doing so I noticed that when I get up to around 80 mph and start applying brakes hard it will shudder but then it clears up if i apply more.
It doesn't happen much at inital application only when i apply it harder.

I tried slamming the brakes a couple of times to see if it was build up on the rotor from the pads and it seemed to have lessened the shuddering affect.

I was thinking this is more of a pad and maybe some warping of the rotor or material stuck.

I'm using EBC Red and Brembo slotted. I don't see any blueing on any of the rotors and the car drives without shudder or vibration until i perform this around 80 mph.

I also happened to notice this after swapping to my style 87's so I'm not sure if there's some wheel imbalance in the equation as well..

Please keep us posted on your findings!

[we350z]

You are right. I am jumping to conclusions and speculating too much without a proper diagnosis. It only seems like it would be the brakes since i just changed them. It may very well be a suspension problem. I just wish there was a more conclusive test to verify the operation of the calipers so that I could certifiably rule them out.

I am very systematic about the way I do things lol. I can't help it I am a programmer so I try to think about all the possible things it could be It's just killing me because I won't have time to take a look at it until this weekend.

I will heed your advice and if the problem doesn't become obvious I will discuss it with my local indy mechanic. If the caliper need replacing or the system otherwise needs to be bled I will let them handle it. Don't want to make matters worse.

Originally Posted by 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.

[we350z]

So I am not the only one with phantom brake problems haha. Good to know that I am not alone. I really need to dink around with it a bit and do the tests. I'll keep you updated on what i find if you promise to do the same.

I too still think that it may be possible that mine are just not bedded in yet. I'm afraid to do the bedding procedure again though if i really do have a stuck caliper. I feel that might just make things worse, who knows maybe it will straighten it out.

Could be anything mentioned in this thread so far:

- Stuck Caliper
- Air bubble in system
- Bad suspension part (i.e. thrust arm bushing, etc...)

Is yours a shudder or jerk? One thing I can say is that mine jerks at almost any speed but only if I apply a good amount of brake pressue. It is hower I beleive more pronouned at higher speeds. Its just one quick jerk and then that's it. I didn't really notice if the car veered but then again the first time it happened i was startled and grabbed the wheel.

I should do a slow breaking test to see if it veers.

Originally Posted by Batm4n

I'm having similar issues. I just did a brake job and after doing so I noticed that when I get up to around 80 mph and start applying brakes hard it will shudder but then it clears up if i apply more.
It doesn't happen much at inital application only when i apply it harder.

I tried slamming the brakes a couple of times to see if it was build up on the rotor from the pads and it seemed to have lessened the shuddering affect.

I was thinking this is more of a pad and maybe some warping of the rotor or material stuck.

I'm using EBC Red and Brembo slotted. I don't see any blueing on any of the rotors and the car drives without shudder or vibration until i perform this around 80 mph.

I also happened to notice this after swapping to my style 87's so I'm not sure if there's some wheel imbalance in the equation as well..

Please keep us posted on your findings!

[we350z]

I talked to my buddy about brake bleeding who may help me out and this is what he said:

Yeah, I've done many, many brake jobs, all custom. I've done many brake bleeding jobs before. You have to do one bleed needle (caliper) at a time, and can take up to 20 minutes per caliper. Kinda the basics, but just in case: As you bleed the brakes you have to refill the reservoir again and again as it's being drained, if it got low then you could have repumped/drawn/pulled air back through the system. If you are using a bottle on the bleeder kit, the bottle MUST be higher then the caliper when you pump the pedal.

All current automobiles take a electronic hand held interface diagnostic tool (looks like a smart phone), I picked mine up from E-Bay, however you can get them @ Autozone, etc. It'll plug in dash and run a diagnostic, if there's something wrong it will tell you a code (you get a little book/CD that translates the code), and tell you what's wrong with the ABS (in most cases), and also anything else (in most cases). Sometimes, ALL that is needed it is for you to clear out the code which resets everything and it goes back to normal, which you erase it with the function on the Diagnostic Tool.

What do you think?

[we350z]

He also added:

Believe it or not I always used the ~$8 kit from Autozone/Checkers, comes with everything and I've reused it for years. Just be careful as the bottle is small, so every couple of pumps make sure the bottle isn't overfilled causing lots of pressure. If you can find a kit that has a bottle the size of a coke can that would be great, the smaller kits have the bottle the size of a shot, no joke. So you have to dump it 5 times just doing one caliper. There are so many diag tools (brands, etc), mine was only $65 on E-Bay, I'd call Checker or Autozone, but believe it or not I've seen some dirt cheap ones @ Harbor Freight. They are nice to have, if something feels wrong with your car, simply plug it in and it'll tell you on the screen whats happening (in most cases, it's not Einstein and can't figure everything out). Also nice if your going to buy another X5, plug it into the dash and it'll tell a lot about the car.

Now, the X5 may have the bubble problem in the ABS, but if it where mine I'd try tackling it. If it doesn't work out it's not like the brakes are going to stop working. I wouldn't be doing HWY speeds, or trying to drive it for a week. But you should be more then able to drive it to the shop if it don't work out, but the pedal well feel much different and the response of the brakes maybe delayed.

So screw it, if it comes down to it I will attempt this myself. Can't be that hard. If I can change my fuel rails and injectors, replace cv boots, do coolant flushes this can't be THAT hard. I need some practice for my other car anyway.

What's the worst that can happen? If i F it up i have AAA.

[JCL]

I agree with your mechanic's comments.

I don't think it is a stuck caliper only because if it was stuck it wouldn't unstick so regularly.

First, resolve the sticking caliper concern. This isn't anything specific to the X5, more just a general procedure. Keep the wheels on. Get someone to sit in the driver's seat. Jack up the car, both sides. Use jackstands. Make sure the wheels spin freely. Have someone apply the brakes slowly, until one wheel is dragging. Freeze the pedal there. Spin the other side and see if the drag is similar. Now do it in reverse, starting on the other side of the car. Push the brake on hard, and make sure both wheels lock up. Release the brake pedal, and make sure both wheels spin freely. End of test.

If that doesn't point to a problem, move to bleeding. First lesson is to always keep the reserve topped up. Check it regularly during the bleeding process. You want to avoid getting air in the system.

Work on one wheel at a time. I would use a hose from the bleeder nipple and a clean pop bottle with several inches of brake fluid in it, with the hose end below the fluid level, but you can do it without that if you open and close the bleeder with every stroke of the brake pedal. Have a cooperative, attentive, helper in the driver seat. Call out your request for pedal up, pedal down, etc, and have them confirm each pedal stroke. It is slow and boring, but attention to detail pays off.

After all this, test drive the car. Make sure it is all buttoned back up, the brake reservoir cap is on, etc. Test the brakes before getting to the street. Once you determine everything is working, test them with a slow application, a hard application, and a so on. Bed them in if you like, but bedding in won't have much to do with your clunk, just with brake pedal feel.

Hope all that helps. I admire your determination. You do want to make sure that you don't let air get in the ABS controller. If you do, no handheld checker will help you, save your money. You would actually need the BMW computer that actively cycles the ABS valves to purge the air, you are not just clearing codes out to resolve that problem. Last price I saw posted on here was in the order of $500 to fix that problem, IIRC.

Good luck, and let us know how it works out.

Jeff

[we350z]

Thanks JCL - I really appreciate the additional advice. I actually haven't talked to the mechanic yet this guy is just a friend who wrenches.

I have learned from prior mistakes that it pays to do your homework I think it probably isn't a stuck caliper either. As for how an air bubble could have been introduced I have no idea either.

I need to look at the service records to see the last time the brakes were bled. I have had the car for almost a year and a half and I know that I haven't done it. I beleive the service intervals call for bleeding every 2 years. So it sounds like they need to bled one way or another.

Your procedure for checking for a stuck caliper sounds like the best one so far. Couple questions though:

0) Should I do this with the car started or at least with the key on?

1) If caliper grips the rotor on one side, even if the other side is not gripping completely - won't that still prevent the other side from turning? I know without engaging the brakes when I turn one wheel the other side turns as well. Aren't the hubs linked via the diff on AWD, or are they independant? Or are you just saying to compare the drag with the brakes applied lightly to see if the wheels turn with the same resistance?

I have noted your bleeding instructions. So if I get the kit with the little bottle just use the apparatus except with a clean coke can instead of the little shot glass bottle? Are you suppsoed to put a little fluid in the can with the hose submerged before you start bleeding?

What you say about the diag unit makes sense. I get the fact that if air gets in the ABS valve that a specialized BMW service computer is required to cycle the valve to purge the air out.

Again - thanks for the tips. You da man!

Originally Posted by JCL

I agree with your mechanic's comments.

I don't think it is a stuck caliper only because if it was stuck it wouldn't unstick so regularly.

First, resolve the sticking caliper concern. This isn't anything specific to the X5, more just a general procedure. Keep the wheels on. Get someone to sit in the driver's seat. Jack up the car, both sides. Use jackstands. Make sure the wheels spin freely. Have someone apply the brakes slowly, until one wheel is dragging. Freeze the pedal there. Spin the other side and see if the drag is similar. Now do it in reverse, starting on the other side of the car. Push the brake on hard, and make sure both wheels lock up. Release the brake pedal, and make sure both wheels spin freely. End of test.

If that doesn't point to a problem, move to bleeding. First lesson is to always keep the reserve topped up. Check it regularly during the bleeding process. You want to avoid getting air in the system.

Work on one wheel at a time. I would use a hose from the bleeder nipple and a clean pop bottle with several inches of brake fluid in it, with the hose end below the fluid level, but you can do it without that if you open and close the bleeder with every stroke of the brake pedal. Have a cooperative, attentive, helper in the driver seat. Call out your request for pedal up, pedal down, etc, and have them confirm each pedal stroke. It is slow and boring, but attention to detail pays off.

After all this, test drive the car. Make sure it is all buttoned back up, the brake reservoir cap is on, etc. Test the brakes before getting to the street. Once you determine everything is working, test them with a slow application, a hard application, and a so on. Bed them in if you like, but bedding in won't have much to do with your clunk, just with brake pedal feel.

Hope all that helps. I admire your determination. You do want to make sure that you don't let air get in the ABS controller. If you do, no handheld checker will help you, save your money. You would actually need the BMW computer that actively cycles the ABS valves to purge the air, you are not just clearing codes out to resolve that problem. Last price I saw posted on here was in the order of $500 to fix that problem, IIRC.

Good luck, and let us know how it works out.

Jeff

[JCL]

Engine off.

No regular bleeding required. The brake fluid is to be changed every 2 years, and that involves bleeding, but if you didn't change the fluid no bleeding would be required.

Correct, you are just comparing the drag.

Use a clean glass bottle, or the bottle that comes in the kit. You have to have the free end of the hose submerged in brake fluid.

[we350z]

Makes sense. I guess the idea is to change the fluid by forcing out exsiting fluid in each segment "run" to each of the calipers which in turn shoild expell any trapped air bubbles that might be in there. So by attaching a hose to the end of the bleeder nipple and submerging the other end in the fluid within the bottle itself this should prevent or greatly reduce the likelihood of air coming back into the line via the bleeder nipple? What about the air in the kit hose between the bleeder nipple and the and fluid in the bottle when you first start bleeding?

As far as the bottle that comes with the kit. Since it is so small, when you need to dump it's contents - I assume you just close the bleeder valve on the current caliper you are working on and then repeat the process, correct? It sounds like the glass soda bottle would prob do it in one shot.

Brake fluid reservoir should be open during this entire procedure to monitor it's level and add more fluid as necessary right? Never let it go below the MIN level right? How many pumps can you typically safely go before needing to add more?

What is the best brake fluid to use and how much will I need? BMW? Motul? What do you reccomend? I have 3 bottles of AP Racing brake/clutch fluid. Does it really matter?

Could my problem then be just that I have old brake fluid in the system? Is it more susceptable to getting air bubbles?

If you are using the bleeding kit with the bottle do you absolutely need to have an assistant? Just to make sure:

After hooking up bleeding kit to caliper bleeder nipple and opening the caliper bleeder valve:

1) Push pedal all the way down
2) Release pedal so it is all the way up.
3) Repeat until bottle is full, ? number of times

So you are saying with the bottle you can leave the bleeder valve open until you fill the bottle instead of opening and closing it with each stroke of the pedal? Is this the main benefit of the bottle - to speed up the process or does it also reduce the risk of introducing air into the system as well?

Lastly, like my friend suggested how important is it to have the bleeder bottle above the caliper?

Is this procedure similar for the clutch in my manual transmission car? Should it too be changed every 2 years?

I sat in on the installation of my street clutch and I remember assisting the mechanic by pumping the clutch pedal. I don't recall him adding fluid tho, just release air pressure via some valve in the engine compartment...

Sorry for the barage of questions, they just keep coming to me lol.

Originally Posted by JCL

Engine off.

No regular bleeding required. The brake fluid is to be changed every 2 years, and that involves bleeding, but if you didn't change the fluid no bleeding would be required.

Correct, you are just comparing the drag.

Use a clean glass bottle, or the bottle that comes in the kit. You have to have the free end of the hose submerged in brake fluid.

[we350z]

I should have just looked at the home page:

http://www.xoutpost.com/articles/x5/b...flush-diy.html