This weekend I pulled the serpentine belt off of the '90 300E to replace it and check the bearings on the front accessories. After some recent posts on fan pulley bearing failures I wanted to take a look. Well, the replacement belt I had was the wrong length, so I'll get to do the job again, but it's easy anyway (maybe 20 minutes if you've done it a few times).

With the belt off I checked each accessory and idler by pushing and pulling to simulate a side load from the belt and also by giving them a spin to listen for "rollerskate" bearing sounds and check the smoothness. I found no clunky bearings and no noise. The fan pulley bearing spins very freely and will keep free wheeling for 15 seconds or so just with a spin by hand. The other idlers will go for 5-10 seconds as well. I think they're in good shape, but it seems that most of the grease must be gone if they spin so freely.

M.B.DOC, Mike Freeman, do these pass the test? Anybody else have comments or experience to share? I'm thinking that I'll leave them alone, but start performing this test every 5,000 miles or so to keep an eye on things. Does that sound like a good plan?

Thanks!

__________________
D.H.

04 ML500
02 E430

Experience is something you don't get until just after you need it.

I wouldn't perform this test often, for the following reason. Assuming you used the tensioner adjuster to remove tension, you will be working the threads on the adjuster every time you perform this check. The threads on the adjuster are a frequent failure point which requires removal of the tensioner, which requires removal of the "y" plate bracket which has an engine opening requiring sealant on the passenger's side hole of the bracket.

I use a stethoscope to monitor bearings without removing anything. You can do this check every day, if you wanted and never bother anything on the engine.

HTH,

someguyfromMaryland

Thanks for the tip. I didn't realize that this was a weak spot. I've only had the belt off 4 times (3 belts and a water pump), so all is fine so far... I'll go with the stethoscope for regular checks.

Can anybody give me advice on the condition of my bearings given what I observed?

Thanks!

__________________
D.H.

04 ML500
02 E430

Experience is something you don't get until just after you need it.