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Old 08-31-2012, 12:08 PM   #7
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Join Date: Apr 2012
Location: Vancouver
Posts: 270
My Ride: 05 M3 Vert/11 X3 M
Originally Posted by dmax View Post
I have a humming after I turn the car off too...never really looked to see what it is as my car runs fine, so I figured it was normal...and I still figure that.

Squeal? Yes, as mentioned, if you didn't replace all three pulleys (2 tensioner and 1 idler) then that might be your squeal source.

Pulleys can be installed at a slight angle...if idler's pin doesn't fit in the notch, it'll be off. Any of the other pulleys might be bad too...doublecheck them when the belt is off (PS, ALT, and WP). Use a hose as stethoscope to isolate squeal if you you want to make sure it's not stuff you really alt and wp. Usually the pulleys on these are fine, but in particular with the wp, if it goes, you'll be stranded or worse if you don't know what to do when the car starts to overheat.

Look well. I don't think your humming is an issue...but the squealing sounds like pulley to me. Replace your belts if you don't know they've been done in the last couple of years. Also, when you put the belt back, did you put it back in the same direction? If not, that could cause squealing right there I think.

The humming is new, unless I have always missed it until the day I decide to correct my headlight aim. The strange thing is that the humming is only there when the car is warm/hot, never cold. Now that I have done some searching, it seems that the DISA somehow regulates torque at low RPM?? Someone correct me if I am wrong. It's also something that you don't want breaking further while still on the vehicle because apparently it can cause some series damage to the block.

I am not 100% that I put the belt on correctly. I will remove and diagnose the pulleys to make sure they were installed correctly. I was just hoping someone could pinpoint the exact issue by just watching the video; wishful thinking I guess.

Last edited by fastsoup; 08-31-2012 at 12:24 PM.
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