Intermittent rattle/knock after cold start when idling

Hi Guys,

Long time lurker, first time poster. I have recently purchased my dream car; a E90 LCI M3 M-DCT. The car has developed a rotational rattle/knock that can be heard in the cabin after cold start when idling. The noise is not present at cold start, only at idle after cold start. Happens intermittently. Monday it was present, Tuesday and Wednesday it was absent, but today it was present. The noise goes away after driving. Could is be Cam/VANOS gear related?

I've tried searching the forum and nothing lines up with what I am experiencing. Ive listened for rod knock (take the car slowly up to 3000rpm 3 times etc.)

I'm relatively new to the car, I love it. However I have never owned a car like it so everything is quite new.

M3MorganAUS wrote

Hi Guys,

Long time lurker, first time poster. I have recently purchased my dream car; a E90 LCI M3 M-DCT. The car has developed a rotational rattle/knock that can be heard in the cabin after cold start when idling. The noise is not present at cold start, only at idle after cold start. Happens intermittently. Monday it was present, Tuesday and Wednesday it was absent, but today it was present. The noise goes away after driving. Could is be Cam/VANOS gear related?

I've tried searching the forum and nothing lines up with what I am experiencing. Ive listened for rod knock (take the car slowly up to 3000rpm 3 times etc.)

I'm relatively new to the car, I love it. However I have never owned a car like it so everything is quite new.

These cars make many strange sounds that you don't hear on other cars. Try to capture an audio clip of the sound and post it here and someone might be able to tell you what it might be.

Mr. BMW wrote

These cars make many strange sounds that you don't hear on other cars. Try to capture an audio clip of the sound and post it here and someone might be able to tell you what it might be.

Here is the link. As I said, goes away after driving even for just 5-10 meters. Drove the car home from my parents tonight and it hasn’t presented an issue as of yet.

I have 2 more videos. Both external. The first one is of the engine bay, I could hear it on the LHS. The second is a video of the drivers (RHF) wheel arch. There is a slight hissing from the oil filler cap so I think it could *possibly* be due to that. I have replaced the cap and cleaned off the peeling paint so that’d explain the leak.

Search lifter tick.

What oil are you using?

If you’re in Australia summer heat will thin out oil and make all sorts or racket. Make sure you use a good quality oil of the proper weight, some people highly recommend against liquimoly

Read.
For New Owners - What I wish I knew when I first bought my E9X M3:

spammysammich wrote

Search lifter tick.

What oil are you using?

If you’re in Australia summer heat will thin out oil and make all sorts or racket. Make sure you use a good quality oil of the proper weight, some people highly recommend against liquimoly

Read.
For New Owners - What I wish I knew when I first bought my E9X M3:

Funny you should mention that, I have used liquimoly 10W60. Would you recommend going to Castrol as they were the original supplier for these cars?

The cap itself could be an issue with the slight air leak. I am going to try to rectify that. The car is booked in to have its oil dropped and filter changed this week as Ive done 5000kms on the LM oil.

Oil choice seems highly personal. I only recommend what I've used. Either the BMW branded 10w-60 or Motul 8100 X-power have worked. I avoided Liquimoly for the reasons i found in searching this site.

spammysammich wrote

Oil choice seems highly personal. I only recommend what I've used. Either the BMW branded 10w-60 or Motul 8100 X-power have worked. I avoided Liquimoly for the reasons i found in searching this site.

Ill take them onboard. A new set of rocker covers is on the way as the magnesium ones are no longer sealing :/

Did you figure out the noise?
Try turning off the AC and see if it goes away.
Also could be related to the idler pulley or tensioner, they do make noise when going bad..

BimmerMan33 wrote

Did you figure out the noise?
Try turning off the AC and see if it goes away.
Also could be related to the idler pulley or tensioner, they do make noise when going bad..

Hi BimmerMan33, only present on idle once warm so not belt related. The car is in the shop waiting for new VANOS covers and rocker covers to be fitted. I posted up a separate thread and my car apparently sounds normal. Can’t be bearing related as it disappears after being driven. Will report back once the car is back up and running.

M3MorganAUS wrote

Hi Guys,

Long time lurker, first time poster. I have recently purchased my dream car; a E90 LCI M3 M-DCT. The car has developed a rotational rattle/knock that can be heard in the cabin after cold start when idling. The noise is not present at cold start, only at idle after cold start. Happens intermittently. Monday it was present, Tuesday and Wednesday it was absent, but today it was present. The noise goes away after driving. Could is be Cam/VANOS gear related?

I've tried searching the forum and nothing lines up with what I am experiencing. Ive listened for rod knock (take the car slowly up to 3000rpm 3 times etc.)

I'm relatively new to the car, I love it. However I have never owned a car like it so everything is quite new.

Did you figure this noise out?

At around 135000-140000km some cars will make a similar sound especially when it is very cold. A friend of mines E90 M3 did something similar and it turned out that a piece of the timing chain guide broke off and blocked his oil pick up, luckily not enough to casue catastrophic damage but it certainly cost a pretty penny to change them and our local tech said that this issue has become a more common occurence. The plastic obviously becomes fatigued due to several heat cycles. The plastic vanos caps can do the same thing so it's definitely something to look at.

The M3g wrote

Did you figure this noise out?

At around 135000-140000km some cars will make a similar sound especially when it is very cold. A friend of mines E90 M3 did something similar and it turned out that a piece of the timing chain guide broke off and blocked his oil pick up, luckily not enough to casue catastrophic damage but it certainly cost a pretty penny to change them and our local tech said that this issue has become a more common occurence. The plastic obviously becomes fatigued due to several heat cycles. The plastic vanos caps can do the same thing so it's definitely something to look at.

This is definitely something I have considered, especially since I checked my drivers side VANOS covers and the intake one had a crack. The car is currently off the road waiting on parts. I posted up some videos up and the engine sounds normal according to other forum members.