[W37V]

Hey guys and gals... I'm hoping that someone might have an answer to this as I'm dumbfounded along with my mechanic.

TL;DR: One can feel a kick through the pedal when releasing clutch pedal. Do you know what is it?

Long version ( all done under warranty):
Background:
I got my car last December with 22k miles on it. It's 2011 6 sp n52. Within 4k miles I noticed that the car was producing a gear rattle (grinding noise) when idling in neutral. I took it to dealership, and they replaced clutch and bearing in transmission. That didn't fix the noise, so the mechanic replaced the whole transmission. That still didn't fix it, so I took the car to another dealership. At the second dealership, they updated car's software which reduced the rattle, but did not eliminate it. They told me it was normal to have such noise. I made piece with it. That was back in April.

Issue:
6 moths later, the grinding noise increased and about 2 months ago, at 40k miles, I started noticing a kick in my clutch pedal when relapsing it. The kick happens under following conditions. Push the clutch pedal. Hold it for about 10-15 seconds, and release it. As the pedal is released, one can hear grinding noise starting up again. Noise and kick is directly related. Kick is more pronounced when the car is uphill or downhill. This week dealership replaced flywheel and put in yet another new clutch kit. Replaced yet another bearing in transmission. At this point I don't think there is anything that they didn't replace. Car has 42k miles.

Tonight, I went to pick up the car and the kick is still there. Noise is almost gone. Now it sounds like a very low grinding. Since the issue is still there, I just left the car at the dealership. Mechanic said that he will have a bmw engineer come to check it out since there is nothing else that he can think of that could be wrong. Kick happens at various realease points and sometimes it happens constantly, and yet at other times it's impossible to replicate the issue.


Does anyone has any suggestions what it could be?

[iDriveanXi]

Wow sorry to hear of your troubles. I do not have any thoughts on what it may be but I wish you luck in getting it all sorted. I also wouldn't accept the car back until it was remedied completely. Good luck and keep us posted

[krhodes1]

A problem with the dual-mass flywheel, assuming this car has one?

[Meeni]

When they replace the clutch pack, they also replace the springs in the clutch plate (or replaced the clutch plate altogether) ?

Also, how are the spline looking on both ends of the clutch plates ? Worn splines can cause driveline lash, which may feel like a kick when engaging.

Also, out of alignment transmission shaft or worse output engine shaft may cause all sort of clutch problems. Usually the cause is a shot ball bearing, which would explain grinding noises.

This is all very speculative, good luck.

[W37V]

Originally Posted by krhodes1

A problem with the dual-mass flywheel, assuming this car has one?

Car does have one. The kick is still there after the DMF was replaced.

Originally Posted by Meeni

When they replace the clutch pack, they also replace the springs in the clutch plate (or replaced the clutch plate altogether) ?

Also, how are the spline looking on both ends of the clutch plates ? Worn splines can cause driveline lash, which may feel like a kick when engaging.

Also, out of alignment transmission shaft or worse output engine shaft may cause all sort of clutch problems. Usually the cause is a shot ball bearing, which would explain grinding noises.

This is all very speculative, good luck.

Both times they replaced everything that comes in the with the clutch kit. I am also assuming, that springs in clutch plate would be "new" since they replaced entire transmission, pressure plates and flywheel. Essentially, everything with the transmission should be "new" at this point. My guess was that it could be worn transmission/engine mount. However, mechanic said that he inspected them and they looked fine.

I m truly hoping that the issue is not caused by the engine. The sole reason for picking my car was hope that I would not have any issues with engine/transmission after the warranty expires (which it did last Saturday).

[335NJ]

Maybe air in the clutch line?

[W37V]

Originally Posted by 335NJ

Maybe air in the clutch line?

It's been flushed at least 3 times so far.

[335NJ]

Originally Posted by W37V

It's been flushed at least 3 times so far.

They used a pressure bleeder from the resovoir correct?

[W37V]

Originally Posted by 335NJ

They used a pressure bleeder from the reservoir correct?

I am not sure. All work has been done at BMW dealership. So, I am assuming that they would use whatever they are supposed to. Mechanic mentioned that they flushed the line and checked slave cylinder.

Just FYI.. I think the closest thing to describing the kick is following: As if you had something stuck under the pedal (i.e. carpet) and suddenly it's freed. OR on some older cars, when wipers are working, you can feel their engagement through pedals.

It's weirdest thing ever. Could it be a clutch pedal itself? But then, why would it be more pronounced on slight incline or decline?

[norsairius]

Originally Posted by W37V

...why would it be more pronounced on slight incline or decline?

This tells me that it's air/fluid related and could otherwise be a helpful hint, but I have no clue otherwise, unfortunately.

Good luck and sorry I can't help more.

[W37V]

Originally Posted by norsairius

This tells me that it's air/fluid related and could otherwise be a helpful hint, but I have no clue otherwise, unfortunately.

Good luck and sorry I can't help more.

Ever since the engine software update, idle remains consistent.

Thank you for your input.

[iDriveanXi]

Slave cylinder maybe?

[335NJ]

Originally Posted by iDriveanXi

Slave cylinder maybe?

That's what I was thinking too.

http://www.ecstuning.com/BMW-E90-335...utch/ES249122/

Or maybe clutch master cylinder.

[W37V]

Originally Posted by iDriveanXi

Slave cylinder maybe?

Mechanic said that he inspected it and it seemed fine. However, it is a possibility.

I guess I will have to wait until bmw engineer comes and inspects it. I will update the post as I get more information. However, please feel free to pitch in any info about possible cause of the problem.

[W37V]

I've been reading below site, and I am not sure it's slave cylinder. However, meeni mentioned engine output shaft. Per the site noise could be caused by transaxle. Since the kick happens as the noise starts up again, I'm led to believe that whatever is causing the noise, might be causing the kick. It would be very embarrassing if the kick is caused by actual couch pedal being bad. Since they spend numerous hours pulling transmission out, and replacing very expensive parts.

http://www.clarks-garage.com/shop-manual/ts-05.htm
http://www.clarks-garage.com/shop-manual/ts-04.htm

[Healey3000]

Originally Posted by W37V

Hey guys and gals... I'm hoping that someone might have an answer to this as I'm dumbfounded along with my mechanic.

TL;DR: One can feel a kick through the pedal when releasing clutch pedal. Do you know what is it?

Hi,

Can you provide more of a description of the "kick"? That may help with diagnosis.

Is it like a flat spot so that as you release the pedal it feels like it hangs up a little and then releases? That could feel like a kick. Or, does it actually push back against your foot without warning? Hanging up could also be the result of a bad master or slave cylinder.

The only force acting on a clutch pedal is the tines on the clutch disk. If those hang up momentarily and suddenly come free, you can feel it in the pedal. However, you said that the flywheel, clutch kit, pivot fork and gearbox have all been replaced, so that's unlikely.

You also mention grinding and rattle in the same sentence. Those are typically very different sounds so would you describe it as a "can of marbles" or a growling sound? With DFM's, it is normal to have the input shaft of the gearbox flicker as a result of harmonics between the DFM and shaft (the infamous death rattle). A new gearbox can still have it. Grinding, however is not normal.

Did they replace the pilot bearing when they replaced the flywheel? That's the only other rotating thing that you haven't mentioned.

Certainly an interesting problem!

[W37V]

Originally Posted by Healey3000

Hi,

Can you provide more of a description of the "kick"? That may help with diagnosis.

Is it like a flat spot so that as you release the pedal it feels like it hangs up a little and then releases? That could feel like a kick. Or, does it actually push back against your foot without warning? Hanging up could also be the result of a bad master or slave cylinder.

The only force acting on a clutch pedal is the tines on the clutch disk. If those hang up momentarily and suddenly come free, you can feel it in the pedal. However, you said that the flywheel, clutch kit, pivot fork and gearbox have all been replaced, so that's unlikely.

You also mention grinding and rattle in the same sentence. Those are typically very different sounds so would you describe it as a "can of marbles" or a growling sound? With DFM's, it is normal to have the input shaft of the gearbox flicker as a result of harmonics between the DFM and shaft (the infamous death rattle). A new gearbox can still have it. Grinding, however is not normal.

Did they replace the pilot bearing when they replaced the flywheel? That's the only other rotating thing that you haven't mentioned.

Certainly an interesting problem!

You seem to describe it perfectly. It feels like hangs for a momentand then it engages. there is no push against the pedal.

Mechanic at the dealership called it gear rattle; however, it never sounded like it to me. Noise from transmission is best described as if there is sand in a bearing (like bad bearing/spindle); however the noise would be easily drowned by the engine nose. Initially, the nose was very low and would disappear over~800rpm, but like I said it got louder and in past few months it would become drowned at about 950 rpm. It sounded as if it was getting worse.

I really wish I could get the printout of all the work that was done on the car so I could have better information on what was exactly replaced vs. just going off what they verbally told me. If someone has such ability, please let me know and I can provide you with my vin. I'm assuming they replaced pilot bearing as the noise was significantly lower than before they replaced dmf.

I never heard of death rattle. I'm currently typing from my phone and it's kind of hard to do the research on it. What did you mean by it?

[drewnel22]

Maybe there is a bend in the master cylinder shaft that when you push it down and release it it "hangs" on the bent part and doesn't slide completely free. Sounds like you have had everything else except for the slave and master cylinders. I would try those next

[Healey3000]

Originally Posted by W37V

Hey guys and gals... I'm hoping that someone might have an answer to this as I'm dumbfounded along with my mechanic.

TL;DR: One can feel a kick through the pedal when releasing clutch pedal. Do you know what is it?

Long version ( all done under warranty):
Background:
I got my car last December with 22k miles on it. It's 2011 6 sp n52. Within 4k miles I noticed that the car was producing a gear rattle (grinding noise) when idling in neutral. I took it to dealership, and they replaced clutch and bearing in transmission. That didn't fix the noise, so the mechanic replaced the whole transmission. That still didn't fix it, so I took the car to another dealership. At the second dealership, they updated car's software which reduced the rattle, but did not eliminate it. They told me it was normal to have such noise. I made piece with it. That was back in April.

Issue:
6 moths later, the grinding noise increased and about 2 months ago, at 40k miles, I started noticing a kick in my clutch pedal when relapsing it. The kick happens under following conditions. Push the clutch pedal. Hold it for about 10-15 seconds, and release it. As the pedal is released, one can hear grinding noise starting up again. Noise and kick is directly related. Kick is more pronounced when the car is uphill or downhill. This week dealership replaced flywheel and put in yet another new clutch kit. Replaced yet another bearing in transmission. At this point I don't think there is anything that they didn't replace. Car has 42k miles.

Tonight, I went to pick up the car and the kick is still there. Noise is almost gone. Now it sounds like a very low grinding. Since the issue is still there, I just left the car at the dealership. Mechanic said that he will have a bmw engineer come to check it out since there is nothing else that he can think of that could be wrong. Kick happens at various realease points and sometimes it happens constantly, and yet at other times it's impossible to replicate the issue.


Does anyone has any suggestions what it could be?

Hi,

I'd like to review this again, just to confirm the sequence of events:

At 26k miles, you noticed what was described by the tech as a "rattle" and as "grinding" by you when in idle/neutral. Under these conditions, only the input shaft of the gearbox is rotating (clutch components and DMF too). The chances of a bad bearing in the gearbox showing up under this unloaded condition are very low. The clutch has nothing to do with it either as the disc and pressure plate are rotating as a single entity along with the flywheel. That is, there is no relative motion between the gearbox input shaft, disc, pilot bearing and pressure plate. Replacing the clutch was probably a waste, but no harm done.

The death rattle I mentioned earlier is a noise that is typical of BMW's when the engine is turned off. At a certain resonant RPM, around 400, the dual-mass flywheel, which is a spring-mass system), "clunks". The floating masses knock against each other briefly and this is quite audible. Confirmation that this is the culprit can be obtained by pressing the clutch down when shutting down and ensuring that the noise goes away. At idle, the DMF and gearbox input shaft cause a rattling as the shaft has rotary harmonics added to it by the unloaded DMF.

My suspicion is that at 26k miles, what you were hearing was indeed the DMF/gear flicker. It sounds different in every car, it seems, depending on the harmonics and amplitude. That may be why reprogramming the idle characteristics helped reduce the noise.

The pedal kick may be entirely unrelated to the noise. The return of the noise could simply be a result of the flywheel settling in. The springs will relax a bit after a few miles and now you may be back in a resonant condition.

When you press the clutch, the noise goes away, as expected, because the input shaft is no longer spinning. As the clutch starts to engage, the shaft spins and the flicker resumes. That seems to make sense. What I can't figure out is why the kick in the pedal coincides exactly with the noise starting up. Are you sure it's 100% correlated? I assume they replaced the throw-out bearing and release fork? Could the crankshaft be out of true? Extremely unlikely but stranger things have happened.

Do keep us posted; this is most intriguing.

[W37V]

Originally Posted by Healey3000

Hi,

I'd like to review this again, just to confirm the sequence of events:

At 26k miles, you noticed what was described by the tech as a "rattle" and as "grinding" by you when in idle/neutral. Under these conditions, only the input shaft of the gearbox is rotating (clutch components and DMF too). The chances of a bad bearing in the gearbox showing up under this unloaded condition are very low. The clutch has nothing to do with it either as the disc and pressure plate are rotating as a single entity along with the flywheel. That is, there is no relative motion between the gearbox input shaft, disc, pilot bearing and pressure plate. Replacing the clutch was probably a waste, but no harm done.

I think the 1st mechanic changed the clutch because he was changing the pilot bearing. From what he described, it comes as part of the kit.

Originally Posted by Healey3000

The death rattle I mentioned earlier is a noise that is typical of BMW's when the engine is turned off. At a certain resonant RPM, around 400, the dual-mass flywheel, which is a spring-mass system), "clunks". The floating masses knock against each other briefly and this is quite audible. Confirmation that this is the culprit can be obtained by pressing the clutch down when shutting down and ensuring that the noise goes away. At idle, the DMF and gearbox input shaft cause a rattling as the shaft has rotary harmonics added to it by the unloaded DMF.

I never experienced such noise.

Originally Posted by Healey3000

My suspicion is that at 26k miles, what you were hearing was indeed the DMF/gear flicker. It sounds different in every car, it seems, depending on the harmonics and amplitude. That may be why reprogramming the idle characteristics helped reduce the noise.

It is possible; however, even after the software update, the noise became louder and more prominent when the vehicle is on slight incline or decline (~3%). If the vehicle is on flat surface, or on incline/decline more than 30% (steep parking ramp), nose would not be noticeable, or almost eliminated. If it was normal, then why did it increase over time? wouldn't it be consistent?

Originally Posted by Healey3000

The pedal kick may be entirely unrelated to the noise. The return of the noise could simply be a result of the flywheel settling in. The springs will relax a bit after a few miles and now you may be back in a resonant condition.

The kick and noise might be entirely coincidental; however, it is one heck of the coincidence (at least to me). To me, it seems like the pedal kicks at the same time when the girding starts happening. However, sometimes I do not hear girding, but do feel the kick.

Originally Posted by Healey3000

When you press the clutch, the noise goes away, as expected, because the input shaft is no longer spinning. As the clutch starts to engage, the shaft spins and the flicker resumes. That seems to make sense. What I can't figure out is why the kick in the pedal coincides exactly with the noise starting up. Are you sure it's 100% correlated? I assume they replaced the throw-out bearing and release fork? Could the crankshaft be out of true? Extremely unlikely but stranger things have happened.

Do keep us posted; this is most intriguing.

I think they replaced everything related to the transmission. On the last visit, they noticed that my lever was not shifting smoothly (it was very hard to move the lever into reverse or 1st). They found grinding on the fork and replaced that too. Now it goes into gears buttery smooth.

All this worries me about the 1st owner of the vehicle. Yesterday, while digging though some documents, I found service documents about this car. It says that the 1st oil change was done at almost 16,200 miles. I got the car at 22k - exactly. When I got the car, it did not had any signs of abuse, but one never knows. I never raced it, or dropped the clutch.

I will def keep you posted.

[Healey3000]

Originally Posted by W37V

It is possible; however, even after the software update, the noise became louder and more prominent when the vehicle is on slight incline or decline (~3%). If the vehicle is on flat surface, or on incline/decline more than 30% (steep parking ramp), nose would not be noticeable, or almost eliminated. If it was normal, then why did it increase over time? wouldn't it be consistent?

Hi,

Well, only one thing comes to mind and you're not going to like it (I hope I'm wrong). Your mention about behavior on inclines takes me down this path.

Engines use thrust bearings to keep the crankshaft lined up, so that the big ends of the pistons are correctly placed and so that the crank sits centrally in the main bearings. These thrust bushings are essentially shims, placed at the front and rear of the crank, next to the last main bearing seats. These can wear over time, but it's very, very rare to see them go before something else fails first, like piston rings or rod bearings.

Given the history (or lack thereof) of your car, I'm wondering if it's possible that the thrust bearings have indeed worn or one is just missing (broke and then dropped into the sump). Abuse can certainly do it, in theory, but still...

When you push the clutch pedal down, you are pushing the crankshaft forwards. That quiets everything. As you release the clutch, the crank shifts back a little and if it's floating just wrong, all the bearings (piston and mains) are rubbing back and forth as the crank moves slightly. hence the grinding noise Remember that as you drive, the crank is being loaded forwards and backwards so the noise may go away at times or show up, depending on the thrust load.

I hope I'm wrong and I also hope you have a warranty!

On a steep incline, it's possible that gravity pushes the crank enough that the floating stops.

[W37V]

Originally Posted by Healey3000

Hi,

Well, only one thing comes to mind and you're not going to like it (I hope I'm wrong). Your mention about behavior on inclines takes me down this path.

Engines use thrust bearings to keep the crankshaft lined up, so that the big ends of the pistons are correctly placed and so that the crank sits centrally in the main bearings. These thrust bushings are essentially shims, placed at the front and rear of the crank, next to the last main bearing seats. These can wear over time, but it's very, very rare to see them go before something else fails first, like piston rings or rod bearings.

Given the history (or lack thereof) of your car, I'm wondering if it's possible that the thrust bearings have indeed worn or one is just missing (broke and then dropped into the sump). Abuse can certainly do it, in theory, but still...

When you push the clutch pedal down, you are pushing the crankshaft forwards. That quiets everything. As you release the clutch, the crank shifts back a little and if it's floating just wrong, all the bearings (piston and mains) are rubbing back and forth as the crank moves slightly. hence the grinding noise Remember that as you drive, the crank is being loaded forwards and backwards so the noise may go away at times or show up, depending on the thrust load.

I hope I'm wrong and I also hope you have a warranty!

On a steep incline, it's possible that gravity pushes the crank enough that the floating stops.

Pardon the language, but you just scared the shit out of me. I truly hope it is not. Warranty just expired on 25th and I didn't get the extended warranty. I am regretting it since it was only $2k for 3yrs or 100k miles.

If it is what you say it might be, I have fully loaded (other than radar cruise control) M-package Space Gray on black Dakota 6sp BMW 328i for sale. I will trow in 3 stage intake along with the car.