[Toadus]

Hi guys.

This is my first post on your forum. I'm wondering if anyone can help me with a couple of small issues I have with my new M2. I have only had the car one week, coming from a couple of years ownership on an M2C, and I absolutely love it!

The main issue is a noise coming from the rear, but hard to tell if it's from outside the car or not. When I drove the car away from the dealership, I immediately heard it and thought maybe the boot wasn't shut properly, as the noise was a metallic "clink" you might compare to a steel clip in a door not correctly seated.

I've been reading through the forum over the past few days and have seen a number of posts relating to suspension noises, but they seem to be a little different. The noise I can hear is not a thud, it's a metal on metal noise. Sometimes it's not just a single "clink", it's two or three together, almost like a rattle. I've had the seats and arm rest down, checked the battery seating, etc. I'm running out of ideas. Oddly, you can go over large bumps and not hear a peep, and then go over the smallest bump and it goes off. What I can say for certain, is that if either rear tyre goes over a catseye, it always happens.

The other issue is to do with the collision warning system. The icon
in the centre console comes on at random. For example, reversed from my driveway this morning, starting going forwards and it came on and remained on for roughly 20 seconds, even though there were no other cars on the road. It also came on again a few miles later, also when there were no cars around.

Anyway! Despite these two issues, I'm so happy with the car. It's been a while since I've owned a brand spanker!

[aerobod]

Originally Posted by Toadus

Hi guys.

This is my first post on your forum. I'm wondering if anyone can help me with a couple of small issues I have with my new M2. I have only had the car one week, coming from a couple of years ownership on an M2C, and I absolutely love it!

The main issue is a noise coming from the rear, but hard to tell if it's from outside the car or not. When I drove the car away from the dealership, I immediately heard it and thought maybe the boot wasn't shut properly, as the noise was a metallic "clink" you might compare to a steel clip in a door not correctly seated.

I've been reading through the forum over the past few days and have seen a number of posts relating to suspension noises, but they seem to be a little different. The noise I can hear is not a thud, it's a metal on metal noise. Sometimes it's not just a single "clink", it's two or three together, almost like a rattle. I've had the seats and arm rest down, checked the battery seating, etc. I'm running out of ideas. Oddly, you can go over large bumps and not hear a peep, and then go over the smallest bump and it goes off. What I can say for certain, is that if either rear tyre goes over a catseye, it always happens.

The other issue is to do with the collision warning system. The icon
in the centre console comes on at random. For example, reversed from my driveway this morning, starting going forwards and it came on and remained on for roughly 20 seconds, even though there were no other cars on the road. It also came on again a few miles later, also when there were no cars around.

Anyway! Despite these two issues, I'm so happy with the car. It's been a while since I've owned a brand spanker!

The most obvious thing I would check is the exhaust flap and it’s actuator mechanism. It typically starts with the flap open then closes soon after engine start. Switching the exhaust flap button (on the centre console) on and off may replicate the noise.

[Toadus]

Originally Posted by aerobod

The most obvious thing I would check is the exhaust flap and it’s actuator mechanism. It typically starts with the flap open then closes soon after engine start. Switching the exhaust flap button (on the centre console) on and off may replicate the noise.

Thanks for the help.

I tried this, but couldn't get any noise to happen when switching it on / off.

I had a friend kindly sit in the back with the back seats down. After some testing, he was able to locate the noise which was coming from the rear right wheel area. Other than that, still stumped! I've informed the dealer

[Shadak]

Originally Posted by Toadus

Thanks for the help.

I tried this, but couldn't get any noise to happen when switching it on / off.

I had a friend kindly sit in the back with the back seats down. After some testing, he was able to locate the noise which was coming from the rear right wheel area. Other than that, still stumped! I've informed the dealer

if you can reprosuce the noise for the dealer thats good, some times its the weirdest things, my dealer is quite good at this, they fixed on my M140 strange noises some of them made by isofix mounts in the rear and also once had to readjust door striker thingy to get rid of a creak.

[abrandonment]

Shipping blocks removed from suspension?

[Toadus]

It's not going in to the dealership until the end of April. I will update with the findings as soon as I can. As long as there's some rough road near to them, they should be able to pick up on the noise.

I drove over some cats eyes recently, and when the rear right wheel hits one, instead of the usual "thump" sound, you hear a "clink". Very odd!

[RootsTootsMagoots]

I has this noise over bumps and it ended it being the license plate frame that the dealer slapped on. I ordered a silicone one from Amazon and used 4 screws to hold it all in place. No more noise over bumps.

[Toadus]

Originally Posted by abrandonment

Shipping blocks removed from suspension?

Thanks. I will mention the possibility to the technician.

[Toadus]

Originally Posted by RootsTootsMagoots

I has this noise over bumps and it ended it being the license plate frame that the dealer slapped on. I ordered a silicone one from Amazon and used 4 screws to hold it all in place. No more noise over bumps.

I will have a look! Thanks.

[Toadus]

I've recorded a quick video of the noise. It's not a great effort! You will probably need to turn whatever sound source you have up to 11

[izzyM2]

This is highly unlikely since your car is new and unmodified. Try shaking the car vigorously while in a stand still by standing on top of the door frame both left and right and see if it duplicates the sound. If it does it's definitely suspension related. I recently replaced my springs and I forgot to tighten the rear sway bars to torque specs and it made a similar sound to yours. It was not loose but torquing it to specs made the sound go away.

[Toadus]

I had my RIS done the other day and the noise investigated at the same time. They discussed with me that they found a slightly loose strap on the driver's side fuel tank, which meant that the tank could foul the heat shield with enough force. I was delighted to hear this, as it sounded very plausible. Sadly, on the drive back home, the same noise was still happening. The mystery continues. I hope it doesn't turn into one of those things that never gets sorted.

The dealership seemed very thorough. They said they have 4 technicians underneath, trying to discover any noise. They road-tested and all seemed well. They were kind enough to lend me a car in the meantime, as they weren't 100% sure how long the RIS + investigation would take. It was another m2! And it didn't make a single peep of noise; so it's not just in my head!

[BroDoze]

Sucks man. I’ve had this before in a few cars. Really can kill some of the enjoyment and sanity behind the wheel.

[Toadus]

I can't yet say with 100% confidence, but I *think* I've figured this out. I've noted a few stretches of road where the noise always occurs, so it's given me the opportunity to do some testing. What I've found is that if I apply the brakes when the rear tyres go over the bump / rough bit of road, there is no noise. If this is the case, it would seem perhaps that the noise is coming from the the rear brake pads? Does the sound in the video marry up with what a loose pad might sound like? Thoughts?

[RockCrusher]

Originally Posted by Toadus

I can't yet say with 100% confidence, but I *think* I've figured this out. I've noted a few stretches of road where the noise always occurs, so it's given me the opportunity to do some testing. What I've found is that if I apply the brakes when the rear tyres go over the bump / rough bit of road, there is no noise. If this is the case, it would seem perhaps that the noise is coming from the the rear brake pads? Does the sound in the video marry up with what a loose pad might sound like? Thoughts?

One can only do so much behind the wheel. Someone has to get his hands dirty.

The noise could be from the pads, although there is hardware to prevent pad rattle. But the hardware could be missing or broken.

For suspected brake hardware, pads, or ?, the car needs to be properly lifted and the wheels left hanging so they can be removed and the brakes inspected for any thing that could possibly account for the noise.

At the same time a check of all the under body panels needs to be made looking for any loose panels. And this would be a good time to check whatever suspension/drive train hardware one can get at for any play or looseness.

[Toadus]

It's now been with the dealership just over 2 weeks and they still haven't been able to tell me what's wrong with it. It seems it has them stumped too!

[BroDoze]

I'm sure you've done this, but pull all of the stuff you can out of the rear of the vehicle (seats, carpet in the trunk, side panels if necessary) and go lie back there while you have someone drive around. That should at least tell you if it's coming from the interior or not, and it may even pinpoint the general area on where to start digging.

[Toadus]

Originally Posted by BroDoze

I'm sure you've done this, but pull all of the stuff you can out of the rear of the vehicle (seats, carpet in the trunk, side panels if necessary) and go lie back there while you have someone drive around. That should at least tell you if it's coming from the interior or not, and it may even pinpoint the general area on where to start digging.

I no longer have access to the car as it's with the dealership.

But yes, I've driven the car with a friend in the back and also with as many items removed from the boot as possible. The noise seems to be coming from the driver's side rear wheel area. Surely though that the noise doesn't seem to occur while braking is a huge clue?

[Toadus]

Over 4 weeks in and still no resolution. They are now swapping parts with a donor M2 and testing, to see if they can find the culprit.

[RockCrusher]

Originally Posted by Toadus

Over 4 weeks in and still no resolution. They are now swapping parts with a donor M2 and testing, to see if they can find the culprit.

It may not be a part.

While rare what can happen is some piece of hardware, or even a tool, can find its way into a body part cavity and make itself known by making noise.

(With my new 2020 M-B cargo van after I had owned it for a while I found what looked to be an ice pick with a curled hook at its business end laying in one of the water channels just at the base of the windshield and under the engine compartment lid. AFAIK it made no noise but of course I removed it all the same. Thankfully it was easy to remove.)

If there is some foreign object in some body part cavity this may not be found by swapping parts as the part can't be swapped as it is part of the car's body/chassis and is not removable.

Underway one method to hear the noise and help locate the source is chassis ears. I would be surprised if the dealer service department didn't have a set of these.

In some cases vigorous shaking of the car can cause the object to make noise and its location can be pinpointed. Once located how the object is dealt with depends.

[Toadus]

Originally Posted by RockCrusher

It may not be a part.

While rare what can happen is some piece of hardware, or even a tool, can find its way into a body part cavity and make itself known by making noise.

(With my new 2020 M-B cargo van after I had owned it for a while I found what looked to be an ice pick with a curled hook at its business end laying in one of the water channels just at the base of the windshield and under the engine compartment lid. AFAIK it made no noise but of course I removed it all the same. Thankfully it was easy to remove.)

If there is some foreign object in some body part cavity this may not be found by swapping parts as the part can't be swapped as it is part of the car's body/chassis and is not removable.

Underway one method to hear the noise and help locate the source is chassis ears. I would be surprised if the dealer service department didn't have a set of these.

In some cases vigorous shaking of the car can cause the object to make noise and its location can be pinpointed. Once located how the object is dealt with depends.

Thanks for the comment!

I don't have all the details on what has been done so far, other than stripping down suspension components, including the brake system. I'm eager to have my car back and also to know what the problem is! 4 weeks is a long time, especially for a brand new car.

[Toadus]

I have the car back and the problem has been resolved.

Apparently there was a bracket of some sort seated near to the rear caliper which wasn't flush in position. As the caliper moved upwards when hitting a bump, it was contacting this bracket. The piece was replaced. It makes sense that the noise didn't occur when applying the brakes, as the rear calipers are sliders, so would miss the bracket as a result.