[JChristie]

I’m hoping someone might be able to help me diagnose the possible cause of a squeaking noise, most likely coming from the engine bay area, on my 2016 M235i with auto transmission.

The noise is best described as a short squeak, similar to something metallic in need of lubrication. You can hear it from inside the cabin, especially if the windows are rolled down. I can consistently replicate the noise when the vehicle is in sport mode. If I’m driving along with minimal throttle (2500-3000 RPM) and let off the gas just the slightest bit, I hear the squeak. Gently reapply and release throttle again, another squeak. Same deal if I simply switch out of Sport mode to Comfort (which again causes the engine RPM to slightly drop) noise replicates. I don’t really hear the noise when driving in Comfort mode, except possibly when the transmission switches from 1st to 2nd (but not confirmed). Also not sure if the noise is present when releasing throttle during hard driving since actual engine noise/active sound would drown it out.

Thoughts? I’m thinking the noise first started about a month back but it’s getting louder. I’ll take it in for a service appointment soon but just wondering if anyone has any ideas.

[Kgare]

It is the exhaust flap actuator. Drive around in sport mode to get the engine warm. Ask someone to to keep ear next to the exhaust while selecting comfort and sport mode.

[JChristie]

Originally Posted by Kgare

It is the exhaust flap actuator. Drive around in sport mode to get the engine warm. Ask someone to to keep ear next to the exhaust while selecting comfort and sport mode.

Thanks! That does seem to be the culprit. Had my family start and stop the engine a few times once the car had warmed up. Could hear the squeak coming from the actuator on the left exhaust each time. From in the car it sounded like it was coming more from the front so wasn't even thinking exhaust.

Nice first post btw!

Any idea if this just means something needs cleaned/lubricated? Or is this symptomatic of a part failure?

Edit: Filmed the actuator on startup. Audio quality isn't the greatest with my phone, but gives you an idea of the noise it makes.

[Kgare]

It is normal and no lubricant is required.

[JChristie]

I don't think it's normal mainly because the noise wasn't present for almost a year. The video really doesn't capture just how loud it actually is, but you can clearly hear it from inside the cabin; even passengers have commented on it. If it was just on startup it might not be as noticeable, but when driving in Sports mode you get continuous squeaks every time you ease off on the throttle.

[xantdieselx]

I've had problems with mine 2x. Cold start you can hear the valve rattling at a high pitch. It's only happened twice so nothing major. Next oil change I'll have the check it out.

[JChristie]

Yep, had the same issue once. On a cold start the valve started rattling to the point that it sounded like the exhaust was ready to fall off. Hasn't happened since.

In regards to my original problem, took some time last week to clean the exposed parts of the actuator. Used a fine steel brush to very gently remove some corrosion on the exposed parts. I also applied a very small dab of a high temp silicone lubricant.

Seems to have worked well because the noise is now gone and the actuator is silent.

I have a feeling though this will be a part that's destined to fail early. Not sure it's a bad design, but it's location means it's exposed to all sorts of road salt, water and constant temperature fluctuations. I'll mention the issues I've been experiencing on my next service.

[EuroDude]

Originally Posted by JChristie

Yep, had the same issue once. On a cold start the valve started rattling to the point that it sounded like the exhaust was ready to fall off. Hasn't happened since.

In regards to my original problem, took some time last week to clean the exposed parts of the actuator. Used a fine steel brush to very gently remove some corrosion on the exposed parts. I also applied a very small dab of a high temp silicone lubricant.

Seems to have worked well because the noise is now gone and the actuator is silent.

I have a feeling though this will be a part that's destined to fail early. Not sure it's a bad design, but it's location means it's exposed to all sorts of road salt, water and constant temperature fluctuations. I'll mention the issues I've been experiencing on my next service.

Many people just unplug it when the valve is open. I think it sounds better open anyway. I use a BMS CanFlap to keep mine open 24/7