[bjt135psu]

Purchased a 2011 mtech with 87k miles back in May. First month or so there were no issues but then I started noticing a squeal. Took it to an area mechanic that I?ve used on other BMWs and they replaced the belt. Below is a list of what I?ve done; it?s squealing worse than ever now.

Serpentine Belt
Replaced Tensioner pulley and idler pulleys
Serpentine Belt
Valve Gasket and oil filter housing gasket
Alternator - mechanic said it was clutch going bad
AC compressor
Serpentine Belt

Each time I replace the belt, it works for a few days/weeks then starts squealing again. I looked at the most recent there are indentation lines on the non-ribbed side.

Any suggestions?

[robthewrench]

If you've replaced all those items, this is a bit tough. Based on your comment about the squealing going away on a new belt, I believe you are getting contamination on your belt and this is causing it to slip / squeal. Look for any source of fluid that could be getting on the belt.

[CaddymanLNL]

or the mechanic replaced a pulley with the improper sized pulley (is that possible>). if your belt seems strained and you are getting noise shortly after these repairs it could be that.

[jt335i]

Although the mechanic you brought it to may have worked on other BMWs, does his place specialize in BMWs and other German cars or is it a non-BMW mechanic/service center that works on various domestic and foreign cars? If that place does not specialize in BMWs, you need to take it to another independent shop that really knows how to service a 335 and have them check it.

I have a trusted mechanic who used to work at same BMW dealer where I first bought my 335. I take my car to him for all my maintenance services and repairs and my mechanic said these 335s require specialized BMW technicians who really know what they're doing and know what are the correct parts to use.