Checking Dual Mass Flywheel DMF - symptoms

S

Sae

Senior member
Hi guys, been trawling threads all afternoon, however, just looking for some main bullet points.
How do you know when your dmf in the zm needs replaced/attention?

What synptoms would you feel or hear?
Vibrations or noises in general? Noises start/stopping/engage/disengaging clutch?

Looks like only a handful have actually had it replaced so just want to know if there was anything that really gave it away?
 
So quick summary of what i can find: (updated)

General Symptoms:
- Rattle noises from gbox area on switchoff with clutch engaged and in neutral
(Apparently obvious from inside and outside car)
- Inconsistent power delivery
- some report an almost two stage clutch engagement when it gets bad
- noisy/lumpy/rumbly sounds when clutch engaged at idle, that disappears when clutch is depressed.

Other notes:
- Seems like dmf is a wear and tear item (news to me) considered part of clutch transfer mechanism
- a lot of folks reckon that a little noise is standard (due to play/tolerance within levels), but how much is ok is not quantifiable without taking the dmf out to check
- they should be changed with every other clutch change, although seems like as a clutch change involves so much labour its best to replace dmf anyways
- inconsistent failure mileages, some fail at over 100k and some well before, obviously in connection with driving styles/racing/abuse
- i havent read anywhere that the dmf fault triggers an engine light or warning of any sort
- now that im searching, seems a fairly common thing to go, but not specifically z4ms

So, my interest in the dmf is that my car is undergoing Insp2, have been told that the dmf is on its way out. I didnt realise it was in trouble (although maybe i wasnt actively looking for the symptoms) before I put it in, so just want to check or 2nd opinion before any work is actioned.

Any folks with other experience? Or missing points?
 
I hady clutch & flywheel (and rear main bearing while they were in there) replaced at 140,000.

Didn't have any flywheel noise, but the pedal just went to the floor one morning. I initially thought it was a master/slave cylinder, but the local Indy had a look and said they were fine and it was the clutch worn past its auto-adjustment limit.

They also suggested i budget for a flywheel too, as it was unlikely that it would be in perfect condition after 140,000 miles.

Priced up using genuine parts from BMW and it was over £3k. Got it done with OE parts at the specialist and it was half that.
 
mmm-five said:
I hady clutch & flywheel (and rear main bearing while they were in there) replaced at 140,000.

Didn't have any flywheel noise, but the pedal just went to the floor one morning. I initially thought it was a master/slave cylinder, but the local Indy had a look and said they were fine and it was the clutch worn past its auto-adjustment limit.

They also suggested i budget for a flywheel too, as it was unlikely that it would be in perfect condition after 140,000 miles.

Priced up using genuine parts from BMW and it was over £3k. Got it done with OE parts at the specialist and it was half that.
Click to expand...

Thanks for the reply, 140k is not bad at all on a single clutch, good to hear that you didnt actually have a dmf fail. My car is just @ 40k, so can only assume an imperfect dmf part to begin with for early failure wrt mileage, however age wise at 10yrs maybe the component has a time life span too.
 
Ok, so car is back from Insp2, the tech demonstrated the tell tale flywheel rattle, which is consistent with symptoms in the switch off test.
In case anyone is interested, I have attached a short clip so people have something to listen to/compare.
In my zeds case, you hear the muffled rattle/flutter after ignition shut off at end of clip. Thankfully its not as severe as the youtube clips I found, so I have some time to source parts and get work done.

https://youtu.be/0vK_awHRfTA
[youtube]https://youtu.be/0vK_awHRfTA[/youtube]
 
Every Z4m i've ever heard has the tell tale clank when switching the engine off, the online reviews also mention its a common issue that's not something you should worry about.

Mine makes the noise when you turn off with the clutch engaged, however when you press the pedal and disengage the clutch, it turns off without a sound.

Is the noise indicitive of an issue?
 
Mine occasionally had the rattle on power off, but it wasn't detrimental to the car's day to day performance...and as I mentioneded earlier, mine lasted to 140k.

Unfortunately mine came back with the 'normal' 1st to 2nd not by gear change. I say unfortunately, as I'd been one of the lucky ones and had never experienced it before. When I complained, the garage told me it was 'normal' and as I had no way to show them how it was before, I reluctantly had to live with it.
 
Kernow-Z4 said:
Every Z4m i've ever heard has the tell tale clank when switching the engine off, the online reviews also mention its a common issue that's not something you should worry about.

Mine makes the noise when you turn off with the clutch engaged, however when you press the pedal and disengage the clutch, it turns off without a sound.

Is the noise indicitive of an issue?
Click to expand...

Thats interesting, it would be good to know how many other ZMs on the forum have this. My gear change, drive, take away is fine, and gearbox is actually much better (probably due to gbox oil change).
There is supposed to be play/tolerance of movement on the flywheel, so maybe the flutter is a common thing, would be cool if another member or two could post a similar sound clip for comparison.

Btw. A good post i found which just explains the basic play in a dmf is below, i dont know if th zm flywheel is significantly different in design, however the vid is just to illustrate possible play in the rotational and z plane.

https://m.youtube.com/watch?v=58nU-f0azb8
 
mmm-five said:
Mine occasionally had the rattle on power off, but it wasn't detrimental to the car's day to day performance...and as I mentioneded earlier, mine lasted to 140k.

Unfortunately mine came back with the 'normal' 1st to 2nd not by gear change. I say unfortunately, as I'd been one of the lucky ones and had never experienced it before. When I complained, the garage told me it was 'normal' and as I had no way to show them how it was before, I reluctantly had to live with it.
Click to expand...

The tricky thing with a lot of this is its difficult to get a view on what normal is. The only way to actually check the dmf is to get it out, but almost a full days labour isnt cheap .
But until then 'normal' is subjective, unless there are some comparisons to other cars with varying mileages or newly replaced dmf/clutch...
 
I really dont believe it to be an issue, ive heard 3 or 4 m's that all make the same noise when being switched off without the clutch depressed. Ive just got in the habit of pressing the clutch when siwtching the engine off now... I have no other symptoms and mines on 57k.
Ive just had an inspection 2 undertaken aswell, the independent who worked on mine was very switched on, he didnt make any comment about the clutch nosie. All he noted was a weeping diff, but again im led to believe they all do that too.

Read the page in the following pistonheads article, they even note the noise when switching the engine off.
https://www.pistonheads.com/news/ph-buying-guide-contents/bmw-z4m-buying-guide-powertrain/33172
 
Kernow-Z4 said:
I really dont believe it to be an issue, ive heard 3 or 4 m's that all make the same noise when being switched off without the clutch depressed. Ive just got in the habit of pressing the clutch when siwtching the engine off now... I have no other symptoms and mines on 57k.
Ive just had an inspection 2 undertaken aswell, the independent who worked on mine was very switched on, he didnt make any comment about the clutch nosie. All he noted was a weeping diff, but again im led to believe they all do that too.

Read the page in the following pistonheads article, they even note the noise when switching the engine off.
https://www.pistonheads.com/news/ph-buying-guide-contents/bmw-z4m-buying-guide-powertrain/33172
Click to expand...

Thanks for the link, the text is comforting...
"Both the gearbox and differential are very rugged and should give no problems. The clutch can make a slight rattling sound when the car is idling in neutral, but this is most probably the release springs rather than anything terminal."
I think I need to get to a meet and listen to other cars to be sure. But will keep an ear on it for now.
 
Both my z4ms have rattled on turn off if the clutch isn't in, my m5 did the same. Absolutely not an indication anything is wrong. Both have also had a bit of transmission noise on idle that disappears when the clutch is depressed, definitely a characteristic of the car.
 
Be sure to let us know what you have done in the end, would be interesting for closure.
But it sure sounds like its a normal trait of the car.
Im not particully worried about mine doing it, and unless other symptoms start to show i wouldnt go spending £1000's on a new clutch and flywheel on what someone advised you unless it was unique to your car, Which in this coase doesnt seem to be.
 
Just going to monitor it for now, apart from the flutter noise there isnt any issue with gear change, clutch engagement or power delivery.
Will update the thread if any further actions taken.

Have edited thread title to be less scaremongery.
 
The gearbox rattle on idle is the input shafts spinning, you can hear it on a lot of front engine rwd cars sports type cars as your so close to the gearbox in the cabin.

Perfectly normal, if you listen closely when you press the clutch you can hear the shafts slow down and then stop.
 
As above, the clatter on switch off (without clutch depressed) is pretty normal I think, at least both S54 cars I've owned have done it and the two others I have driven in my time also did so.
Likewise at idle if you depress the clutch you may stop the very slight 'rattle' you can hear around the trans tunnel. Redun explains perfectly why that is.
Clutches and dmfs are well known to go far north of 100k miles on these cars :)
 
Hi,

I have the 3.0Si, when I first purchased it as an AUC car from BMW I had both of these symptoms investigated by the dealership (rattle when turning off the engine and slight DMF noise when idling). This is the report back from engineers and confirms what people have been saying on the forum. I know the 3.0Si and M are very different cars but it does back up what people have been saying about the issue, it seems to be a characteristic of the car.

Hope this is of some use!
 

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