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Help identify this - belt drive squeal

698 Views 2 Replies 2 Participants Last post by  dragonflyer
2008 R350 Both idler pulleys and tensioner are new. So is the water pump. Squeal, like loud cricket chirping, appears to be coming from upper idler but when I install old one it sounds the same. Squeal is most pronounced when engine is cold. Could this be the new aftermarket water pump? I tried using metal bar as statoscope on bolt heads of two idler pulleys but heard nothing like the squeal on them. I can’t do that to rotating hubs like water pump, alternator, ac & steering pumps but the noise appears to be coming from opposite side of drive belt at upper idler.
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what brand of water pump did you buy? Hopefully you bought a higher quality one.
The water pump is tricky as the weight of some aftermarket is so much lighter than the factory OEM. I stick w OEM if I were you.

MAke sure you match correct waterpump since R class had several engine front style.

It is imperative to match the correct engine number with the idler pulley, tensioner, lower pulley and water pump.
I paid $54 for the water pump on eBay, there are cheaper and there are more expensive ones. I will chime back after reinstalling the original pump. Definitely a sign of poor quality of some of these aftermarket parts.
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