Belt Tensioner Info?
 

As a noob, can anyone clarify the serpentine belt tensioner differences on the M44 - 1998 (10/97 build) 318Ti? I had to replace the alternator recently (that's what happens when you try to charge a battery with a shorted cell, although it WOULD start the car!) and now I get a pretty loud whine from the alternator/tensioner area, worse at an idle. From what I can tell, some engines have 2 idler pulleys - one on the alternator itself and one on the tensioner, and others have only the one on the tensioner. There seem to be both hydraulic-style and mechanical tensioner assemblies. Mine appears to be a mechanical tensioner with a 16mm hex-head bolt which releases counter-clockwise and with only one idler pulley. What do I order to replace the idler pulley? I see idlers, but those are supposed to only be for the hydraulic-type tensioners. I see complete mechanical tensioner assemblies, but those are pretty pricey if it's only the pulley bearings gone bad. Can somebody sort out this tensioner mess for me? BTW - already replaced the one remanufactured alternator which whined with the one on there now - which also whines so would like to try the tensioner pulley if it's not too much...

Try looking it up on realoem.com. Just type in your VIN and it'll tell you what you need. You might also check your water pump, the bearings are known to wear out which causes your belt to vibrate which makes the tensioner chirp.

RE: Tensioner Question
 

The water pump was replaced about 10K miles ago and all was quiet before the alternator swap.

Sometimes releasing the tension on a belt allows the bearings in some other part to unload and they can't re-align. Idler Pulley's have done this to me a couple times. AS well as AC compressors clutch idler bearings.

Good Luck
Dave

Looks Like the Whole Deal...
 

I looked on realoem.com and saw the two setups for my VIN - both with what appear to be mechanical tensioners. One had two idlers, the other just one. Mine is the one-idler setup, which realoem.com seems to indicate goes with a 70-amp alternator while the two-idler setup goes with an 80-amp unit. Don't know what was on there originally - only that it was Valeo - nor do I know exactly what the reman'd Valeo on there now is, amp-wise. Checking out a bunch of parts sites (Bavauto, etc. it does look to me like you can't get just the pulley for the mechanical tensioner - you have to get the whole thing at >$50 instead of just the pulley at <$20. Typical...

Just get one from one of the part-out threads:wink:

Thanx
 

Yeah, thanks
I'll give that a try if decide that it's gonna help the whine. Gotta try to ID the problem first, tho... Could be belt, pulleys, idler, or bearings in new alternator, PS pump, or water pump. Keeping fingers crossed since noise is there but nothing's getting worse...:smile:

I guess I've got the tensioner issue resolved - it's mechanical tensioner, single idler, and it all comes as one unit - no cheap fix.