I bought a 2015 MCS with Manual Transmission about a month ago with 40,000 miles. The past week I started to hear this high pitch sound intermittently. However, today it happened right after starting the car and continued while driving at low & moderate speed but seems to go away when driving at high speed on the freeway. That sound will stay on after coming to a full stop and stays on indefinite while the the engine is idling.

I did try a lot of things but nothing made the sound stop:

A/C On/Off with various air circulation cycles
Checked for any loose hoses in the engine compartment
Replaced Cabin & Engine Air Filters

I am attaching the Sound file and tried capturing the Sound while parked and idling. Hope you can hear the annoying sound! Thanks for any suggestions to diagnose the source of this sound.

 

Was not able to hear anything from the clip.

If the noise tends to follow end speed this can be a bad accessory drive idler roller or tensioner roller bearing. Most of my cars have gone up to hundreds of thousands of miles with nary a problem in this area, while another car developed a noisy idler roller bearing two times separated by around 75K miles. The first time the symptom was a "dry bearing" sound. The 2nd time was a high pitched intermittent "chirp".

If not a noisy idler roller bearing it can be a water pump. With other cars I removed the belt and checked for any excessive idler roller/tensioner bearing play and any play form any of the accessory drives. My experience is the accessory drive with any play is the bad drive. In the case of one of my cars this proved to be the water pump. It was not making a high pitched noise but a low growl-y/grumble-y noise.

Because at first it was not clear to me the noise was coming from the accessory drive I removed the serpentine belt -- noting its routing and direction of rotation so I could install it the same way again -- and started the engine and let it run only long enough to confirm the noise was not present. The noise was from the accessory drive. Then it was a matter of like I mentioned above checking for a bad bearing or an accessory drive with bearing play and the water pump had the play. Not much but it had some while the other accessory drives had none.

Another clue was the relatively new belt had a sharp edge. Serpentine belts should *not* have any contact of their edges with any pulley. The belt was making contact due to the play in the water pump which caused the belt to mistrack and make contact with the pulley sidewall..

Another time with another car a high pitched noise was present under some conditions and the problem turned out to be a bad high pressure bypass valve in the power steering hydraulic system. Because the power steering pump also provided hydraulic power assist to the clutch I could fully depress the clutch pedal then release it and the noise would be gone. But if I rev'd the engine the noise would return. Had to replace the power steering fluid tank. The valve was part of the tank and not available separately and not field serviceable anyhow.

Does the engine run ok? A high pitched whistle can be an intake air leak but the chances are the engine would show some signs of an air leak. Also, the leak might fade away at higher engine speeds.

 

Thanks RockC for your comprehensive input and sorry the Audio Clip was not audible. I used my cellphone to capture the high pitch whistle but the engine noise muffled it. I'll try again.

The high pitch sound is the same regardless of the RPM and the car runs perfectly in all 3 modes (Green, Mid & Sport). One more observation, at times the whistling stops when coming to a full stop at a traffic light. However, after depressing the clutch & engaging the 1st gear the same whistling noise will come back immediately (but not always).

Again, appreciate all the information and I know it is going to be a very tricky to nail down the source of the problem!

 

Does the squeal increase with RPM or no? Does it go away if you put the car in reverse? I couldn't hear the sound well in your clip... does it sound like these links?


I had a similar issue. I could only get the sound to happen after extended driving at highway speed (like 2+ hours typically) and then downshifting for an exit or something. That would usually trigger it. It turned out to be an issue in the transmission. We don't know exactly what it was as MINI doesn't open the trans up to inspect it but the feeling is there was a bearing or something rubbing that shouldn't have been. I got a new transmission under warranty as a result... took close to 20K miles of chasing it down before we finally figured it out. I had no driveability issues of any kind (except massive embarrassment at the sound). The service manager diagnosed it by seeing that the sound went away in reverse and came back in first gear. Remember that your trans doesn't stop spinning until it changes direction, which is why you still hear it at idle.

 

Oh man I have one of the same sounds, and pretty sure my warranty is up. Gotta talk to MINI right away.

 

Well, I got nothing more but my Porsche 996 Turbo emitted a high pitched noise under some circumstances. Engine and drive train had to be up to temperature. I'd roll up to a stop and as is my habit shift into neutral and let the clutch out. Then I'd hear the noise. By experimentation I found I could cause the noise to go away by depressing then releasing the clutch pedal. But I could also bring the noise back by just reving the engine a bit.

Turned out to be a "bad" high pressure bypass valve in the power steering system specifically the fluid reservoir. Why working the clutch affected the noise was because the clutch pedal was boosted and piggy backed onto the power steering hydraulic system for its power boost. While the tech told me there was no harm in continuing to use the car the noise proved to be a bit irritating so I had it "fixed". The fix was a new power steering reservoir with a new high pressure bypass valve. The valve was not serviceable as it was built into the reservoir.

 

Sorry to resurrect on old post but I am having the same issue with my new 2024 JCW F56. Just had the transmission, clutch and flywheel replaced with only 500 miles on the car. This morning the squealing has returned with the new transmission. Very frustrating. I had to wait a month and a half for the parts to come from Germany. I now fear the same wait!

Anyone else having this issue. I feel if I am having it with 2 transmissions there has to be many others with this same issue.

 

HI. I have a F56 Cooper S, 2016, Manual.
I have same noise after hard driving.
With clutch pressed and "playing" with 1st to 3rd gear, the noise changes according the expected rpm if clutch is depressed. So I believe:

1.- It is the gear box, not the clutch nor the engine.
2.- It comes from the main gear box shaft that connects to the crankshaft

I think it is pressure related inside the gearbox and the lipseal at the shaft end releases the pressure as a whistle. When I continue driving gently again, the noise is gone.
Is there any Vent, Valve, or anything related to air pressure (vacuum) connected or interacts with the gearbox?. Or maybe the temperature inside the gearbox creates pressure and when cold it is gone?

Cheers

 

By the way. @RockC reminded a Porsche pressure/lipseal related issue together with a whistle, solved by finding the pressure undesired effect (Vent, Valve, etc.) into the gearbox. I saw that in a Porsche forum (water cooled versions)

 

So, after 2 transmission replacements, a clutch replacement and a flywheel replacement the sound was still there. The dealership had an engineer from Mini come in after they had my brand new JCW for 3 months. It was found that the engine was defective and had bad bearings in the area where the transmission is attached. My engine was replaced and the noise is gone. They had thought it was the transmission the whole time as the noise was coming from the transmission area. They even used a devise attached to the engine compartment to pinpoint where the noise was coming from. The dealership had my car for a total of 4 months. They did supply me with a loaner and compensated me well.

 

Thanks for the update. Nice you had it solved. My car is not under warranty :-(.
Interesting to know about the bearing you mentioned. I do not have a sectional drawing of the engine/transmission, but I can guess the only bearing in that area is the one before the flywheel end.
In my case the noise or whistle varies with the transmission shaft RPM (without releasing the clutch). I just tried with the engine at idle and the car moving about 15 km/h. With the clutch pressed I changed from 1st to 3rd gear, whistling badly in relation with the RPM of the selected gear. Under the same conditions, 4th gear and up: no noise.
I believe is transmission RPM/Temp/air pressure(?) related, but like in your case....It can be anything, including the bearing near the flywheel .
Congratulations for solving the issue...I hope in my case is not the engine :-((((.
Thanks again