Which bearing is trashed?

Hi all. I've got 3 symptoms:

~ Intermittent sounds like a bearing getting ready to go – not shrieking, but periodic chirping in sync with the serpentine belt, as well as occasional more grinding/gnashing noises;

~ Occasional bucking, like a power drop, or a bearing getting ready to seize;

~ Losing coolant; I’ve had to add fluid three times in the past couple months;

When I removed the serpentine belt to isolate, most of the symptoms went away. So I am 98% sure it’s in the serpentine circuit, NOT timing stuff.

(The only symptom that didn’t go away is a very slight timing belt chirp that is exactly in sync with one revolution of the timing belt. I'm guessing that some component within the timing circuit also may have a pending issue, or the belt is slightly rubbing. But with the serpentine belt removed, none of the bucking, none of the much more audible chirping or gnashing.)

With the serpentine belt off, I rotated each of the serpentine pulleys/rollers, and could not find one that was clearly the culprit. Of the two rollers, the tensioner pulley had more play. The power steering, AC, and alternator felt fine.

Is it possible for the bearing on the tensioner to go so bad that it could cause the belt to grab and the engine to buck?

If so, is it advisable to replace the entire tensioner, or just the pulley?

I would have guessed water pump, with the slow coolant leak. But since it's clearly not the WP bearing, with serpentine removed, that's probably an unrelated drip somewhere?

Note: I am driving it now with serpentine back on. Most noticeable symptom is slight bucking/ power cutout every couple minutes or so.

Thanks, and I’ll take my answers off the air.

Rolf in MA

Check the alternator pulley one way clutch.

Thanks oilhammer!

I'm remembering doing this on a previous TDi now.

Symptoms have abated for the moment. Going to pick up parts at ID over the weekend, and hope nothing blows up before then.

Fingers crossed!