My 2011 328xi has about 125,000 miles. I bought the car with 35,000 and have not changed the serpentine belt or tensioners. On Friday morning it was a bit cold out and when I arrived at work after about a 30 minute drive the engine was squealing loudly at idle.
The noise has been intermittent since then and takes a bit of driving (warm engine) to start. Then it subsides a bit as the RPMs increase to became nearly inaudible at highway speeds and 3,000 RPMs. But at idle it is extremely loud and high pitched.
I was thinking to replace the serpentine belt and idler arm pulley. But admittedly have no idea where the noise is origniating. Yesterday my best mechanic friend (good with engines but not BMWs) thought the sound may be coming from a bit lower in the engine compartment guessing an air pump?
Any guesses if I should just R&R the belt and idler pulley? or ?
Definitely do the belt, idler, and tensioner. If that belt shreds for any reason, it can get stuffed through the front crankshaft seal where it can wreak havoc inside the engine.
Thanks, I replaced the belt and idler arm pulley Wednesday night the sound disappeared. Gone Thursday all day as well. However sure enough this morning it returned along with the slow/rough idle. I didn't replace the tensioner. Should I look into that air pump? or tensioner next? should I replace just the tensioner pulley or the entire assembly?
The tensioner and pulley is one assembly.
There is no such thing as an air pump on your BMW. Are you talking about the a/c compressor? For what it's worth, I've had a few N52 power steering pumps make noise. But it's a fairly distinctive sound. Kinda like a whining more than a squealing.
ASE and BMW Master Certified Technician
Thanks White, the squealing was from the very bottom of the belt area, could have been the A/C compressor, but turning the A/C on/off seemed to make no difference? also turning the wheel didn't change the sound at all either?
Also while at Autozone I thought they would sell the pulley only for about $60 and I paid $115 for the pulley and tensioner?
I think the part numbers were
PULLEY - BMW (11-28-7-535-860)
BELT TENSIONER - BMW (11-28-8-624-196)
Here is a link to a 15 second video recording of the sound if that might help anyone, thanks!
https://www.flickr.com/gp/127124632@N03/91125F
Did you ever figure out what the squealing sound was? I have this same issue and it is an almost unholy type of irritating. I found that spraying lubricant on pulley system and fan bushing/bearing area seems to eventually quiet it.
To me that sounds like a dry bearing.
Expect it to seize at some point IMO.
A mechanic can trace that in a moment.
Put a stick or such on the various components (safely) and listen for the vibration transfer.
Pull and tensioner replaced?
If so, what about the fan as noted just above?
I'm taking my vehicle in to get my CEL codes checked (all related to the VVT system, yay) so I'm going to have them check out the squealing. I've driven all over the world in a wide variety of vehicles. This squealing is the most annoying sound I've ever heard in a car.
Last edited by T3HN4T3R; 01-22-2018 at 11:43 AM. Reason: I can't words apparently.
Alright so...
Mechanic pulled off my oil filler cap and the insanely high whistling squeaking sound immediately stopped. Apparently it's directly related to the PCV valve on the driver's side firewall side of the valve cover. Apparently that kind of vacuum issue can rip the rear main seal into the motor. Apparently this is also a thing: https://vanos-bmw.com/valve-cover-n5...mw-11127552281
Thread I found related to all this: http://www.e90post.com/forums/showthread.php?t=1311941 (fix is on the last page)
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