After I had the fan clutch replaced on my 94 S500, I started hearing a low pitched noise (whine) when the engine hits the 1500rpm mark. It seems to be coming from the engine compartment. The repair shop that did the work told me it had nothing to do with the fan clutch and that it was coming from the tranny tunnel. I've taken my car to this shop a couple of times. they'll fix one problem but then another one would come up after I get the car back from them Needless to say, that was the last time I went to them. Anyway, any ideas regarding the low pitch noise? Thank you.

could the noise be the sound of a working clutch that you just need to get used to again?
are there any other conditions it occurs under? like acceleration or deceleration?

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RIP: 80 300SD
RIP: 79 450SEL
2002 E430 4matic (212,000km)
2002 ML500 'sport'

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FACEBOOK: PANZER450

That sound wasn't there before the fan clutch failed. It's a steady sound that comes up when the tach hits 1500 rpm. The pitch varies a little when you accel/decelerate but only when it's above 1500 rpm. Below that, it goes away.

Loose Exhaust hangers, could cause an RPM specific resonance, Flex Discs would cause a road-speed specific resonance. Since the fan clutch is new, it can be ruled out to the point of maybe there is a pulley that is cocked slightly off kilter causing it to resonate.
Does the sound change as the engine warms up at all?

__________________
RIP: 80 300SD
RIP: 79 450SEL
2002 E430 4matic (212,000km)
2002 ML500 'sport'

____________________________
FACEBOOK: PANZER450

Thank you for the suggestions. I'll check the exhaust hagers, flex disc and belt pulley(s). Flex disc is good possibility because I remember , when I called the shop about this, they checked it out and told me it was coming from the transmission tunnel, had nothing to do with the fan clutch and that it was going to cost me more money to fix it. My feeling is that they "fixed" it so that I go back to them for more repair work, $500.00 min......I found out from other ex-customers that they went thru the same thing with these guys.

No whine/noise during engine warm up.

With THAT variable, it's starting to look more and more like an exhaust vibration.

__________________
RIP: 80 300SD
RIP: 79 450SEL
2002 E430 4matic (212,000km)
2002 ML500 'sport'

____________________________
FACEBOOK: PANZER450

Check your fan bearing bracket. Once people start messing with that bolt that holds the fan clutch to the bearing bracket, that accelerates the death of the old bearing bracket causing it to wobble, screech, whine....etc..at least that is what happned with mine...

look at it while the engine is running, and rev the engine while you are outside of the car and listen carefully....

just an idea worth checking....good luck!!!

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1993 300E, 2.8 M104 .....

What/how do you mean?

Thanks. Will check this out.

My air pump makes noise when I first start the car when cold. BTW - same engine etc. '97 S500

Does the noise go away after the engine has warmed up or does it stay?