My brother's 190D 2.2 is squealing rather badly. The tensioner pully and belt were replaced last year when it had a different squeal. I didn't do the previous work, an MB guy did. Anyways, if I spray the back of the fan clutch with WD-40, it shuts up. I am careful to not get any on the belt. Does these seem like the culprit or would it be something else? I was hoping there was a way to at least check that it comes on as it should.
Thanks
David

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2000 Honda Accord V6 137k miles

1972 300SEL 4.5 98k miles

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