Diff Noise after a drive

[DTP1980]

I have always experienced this after any kind of drive when the car gets up to temperature. I park the car up. If ignition off. And within 5 seconds I get a loud mechanical squeak from the rear, almost like an un-lubricated metal hinge. Searched the forum with no obvious luck. It sounds like the diff to me. It’s not the exhaust valves moving back as the noise occurs irrespeive of the mode i’m in.

Of course, I tried to record the issue this evening, and it didn’t happen. But 8/10 times it does it.

Dealership claims it’s the diff ‘relaxing’. But my M3 never did it and none of my LSD’d Audi’s ever did it.

Is it just mine, or does everyone’s car do it?

Car is back in tomorrow regardless, but I need additional backup from fellow users.

[M5Rick]

When I park mine up I too hear a mechanical squeak only quieter but I know it's the exhaust butterflies shutting.

[SapphireM5]

So you go for a drive, come back home shut the car off and after a few min you hear the squeak? Are you sure it's not the exhaust flaps? They are vacuum controlled so once the car is off and vacuum is depleted, they close. Just a thought

[TLK]

I get it also, it sounds like a quieter version of the electric parking brake. Doesn't take long, I often hear it as soon as I'm getting out of the car

[rsuhandy]

It is almost certainly your exhaust valves closing due to loss of vacuum.
You can test it by wiring your exhaust open, and if the sound goes away then you've found your culprit.

[Craze]

Handbrake most likely
Almost all of my bmws do this

[M5Rick]

When you park it up switch off the engine and quickly go to the exhaust pipe outlets;You can see the exhaust flaps shutting with the corresponding metallic sound.You may want to give the flap shafts a dose of WD40 to quieten them for a while.

[rsuhandy]

Originally Posted by Craze

Handbrake most likely
Almost all of my bmws do this

If it is the handbrake then OP would have ignored the sound every time he used it in the past. It is easy to actuate the electronic brake after all to attempt to recreate the sound.

[M5Rick]

Originally Posted by rsuhandy

If it is the handbrake then OP would have ignored the sound every time he used it in the past. It is easy to actuate the electronic brake after all to attempt to recreate the sound.

Agree you can find out in a second by switching engine off and clicking on the park brake, you should just hear a muted hum.

[DTP1980]

Thanks everyone.

Comments discussed with head technician at the dealership and confirmed that ‘they all do that’, it’s the exhaust valves closing. Apparently they are particularly bad on the 3.0i petrol engines too.

At least it gives me something to aim for in attempt to quieten it down in the future.

[///3dkn]

Originally Posted by rsuhandy

It is almost certainly your exhaust valves closing due to loss of vacuum.
You can test it by wiring your exhaust open, and if the sound goes away then you've found your culprit.

THIS.

It's the exhaust flap. Mine has been doing this ever since I bought it. Have someone go behind the car and watch the exhaust flap close after you shut it off.

A quick google will give you this thread:

https://f10.m5post.com/forums/showth...=854465&page=2