While disassembling many of the parts in the engine compartment of my R53 I did not realize that the serpentine belt idler is on an eccentric bolt, and I did not index it for reassembly to its original orientation. What is the secret to its reinstallation? TIA.

 

The idler is not on an eccentric bolt, if it is running like a cammed bolt you need to either buy a new idler pulley or make sure the aluminum spacer is bottomed out on the idler before installation.

We've got the idlers on hand if you need one, feel free to give us a call.

 

I'm pretty sure it is eccentric . . .

 

This has piqued my interest as I'm planning on replacing my crankshaft pulley, serpentine belt, serpentine belt tensioner, idler pulley, timing cover gasket, crank seal and internal oil pump seals in the not too distant future.

When I read your thread, I wasn't aware of an eccentric bolt setup on the idler pulley, so I immediately looked up photos of idler pulleys on vendor's sites and while there were never any "straight-on" photos, the bolt head did appear to be slightly off center axis.

Do you have a photo of your pulley from a straight-on angle?

This is the best I could find to illustrate my point...

 

Here is a shot from the front and back of the idler pulley, no eccentric. There is no way of keying the pulley on or setting eccentric offset, just torque to spec.

 

Thanks for clearing that up Nick...

JAB... Any chance you have an incorrect or third-party idler pulley installed?

 

No chance . . .

 

Well now I had to snake an inspection mirror down the side of my engine,
shine a light on it and check mine out to satisfy my curiosity.

Centered.

And my car is the same year ('04) as JAB's, albeit a pre-facelift.

Hmmm...

 

Well, this is interesting. I took it apart and am fairly certain that it was NOT designed to be eccentric, but for some reason the outer washer had an elongated hole that permitted it to be eccentric if the installer so chose. Last person in the area was Way when he installed an ATI crank damper for me at the Dragon several years ago. Way, any insight?

 

A damper install shouldn't have anything to do with the idler, chances are that you're just now noticing a faulty idler because it's off and in your hands.

They're not too uncommon of a failure item, usually replacing them due to a noise though.