I give up

I have a strange grinding noise that sounds exactly like a collapsed bearing and it can only be heard from inside the cabin, but it is not aircon related as I can hear it clearly with the aircon/fan off. It is also not drive or brake related as I can hear it when my vehicle is parked in my garage idling. I have no oil leaks, but the grinding frequency changes with the revs. I suspected one of the pulleys in front had a damaged bearing, but once again I cannot find or hear it clearly in the engine bay. My biggest worry is that it is the turbo again (which was refurbished 1 year ago) as it is situated right behind the dashboard centre which is where the noise seems to be coming from but I have only experienced turbo power loss once since it was refurbished. Merc have taken the pulley belt off and all the pulleys seem fine and the turbo pressure was measured and is spot on. The aircon and fan work perfectly so what could it be? Engine temp is constant and where it should be. I am very confused and annoyed because I want to sell the car, but can't until this is resolved. My ML is a 2006 320cdi with 175 000km/110 000miles on the clock and is up to date on every service. The turbo is the only thing that has given me major trouble in the past - other than that it has been a pleasure to own.

pharaoh

Sounds like the front diff, have you checked that?

06e320cdi

Can you post a sound clip?

I give up

After absolutely crapping my pants when I read multiple posts about a not so common problem with the Cdi's - crank bearing #1 failure and the massive repair bill, I gave up and dragged my car to AMG conversions who gave me great news. They whipped the pulley belt off and found the culprit was a failed airconditioning compressor grinding away. The compressor is located right next to the crankcase which was why I feared the worse case scenario. I have never been happier to part with R 6000.00 for the replacement bill in my life. It was checked 1 month ago when I first heard the noise, but typically the faulty part decided to behave just before I pulled into the dealership so they could not find a thing wrong with it. I am also glad it was not the turbo. I am too stoopid to figure out how to post the sound, but it is a nasty collapsed bearing grind that gets worse when idling at a traffic light. It then disappears at exactly 1500RPM - the exact same symptoms as a #1 crank bearing failure. Happy days.

I give up

Ps. The reason I discounted the aircon compressor as a culprit earlier on was because I thought switching the aircon off at the dash disengaged the compressor, but not so as was pointed out to me in the workshop. The aircon compressor runs full time on the engine pulley as it does not have a clutch system like older generations of Mercs which shut the compressor down when not in use. Not bad for permanently running and lasting 175 000km.

06e320cdi

You also mentioned removing the belt which threw some of us of, if you removed the belt, the AC pulley would not have been turning. In any event, Great news on the culprit!!