E85 - Funky Serpentine Belt Squeal

[ann.nonco]

I've recently found that the belts on my 2.2 Z4 (M54B22) squeal when it's cold outside or has been sitting for a while.

Our mechanic has taken the belts off and checked the pulleys for play but they have marked it as fine. As per usual the squeal doesn't happen when it's at the shop annoyingly.
Googling and referencing this issue says it's either the belt, tensioner, idler pulley or the alternator bearing.

The loud noise usually goes away after 60 ish seconds then lowers to a very low squeal for the whole journey, then somewhat if I turn off the engine then restart the sound is completely gone.
This makes me suspect that the belt is slipping and with every restart it might cause the belt to move a little.

Any thoughts would be of so much help.
Thank you!

[DMike]

Hi,
On my M54B30, which had similar symptoms and which has an identical serpentine belt, changed the pulleys but it was the belt tensioner in the end. INA, an OEM supplier, makes a conversion kit that replaces the original desing spring loaded tensioner with a hydraulic one. The hydraulic version is more robust and also recommended in a TIS bulletin. On the other hand, if you have managed with a spring tensioner to date and can source one, why not keep it simple and just replace it again in twenty years or so…

I think we’ve had a couple of earlier threads about this.

[DMike]

I think we’ve had a couple of earlier threads about this.

https://z4-forum.com/forum/viewtopic.php?t=124267
https://z4-forum.com/forum/viewtopic.php?t=140884

[ann.nonco]

Thank you so much!
I recently got the belts looks into by an indie shop and they have reported that both the A/C and main belts are fine - but the tensioner was bad on the main belt side so a new tensioner it is!

When they spun the pulley it made the squeak that we were looking for