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Discussion Starter · #1 ·
Well, the trusty 300TD has come up with a bit of a mystery thing now. The engine HUMS. The hum is directly related to the engine speed, and I've narrowed the source down to the area around the first cilinder.
As for the kind of humm, picture yourself a miniature rotory engine. Like, ZZZIIIIIIIIING, constant, no interruptions.
I've recently replaced the waterpump and radiator, but this can not be related in my view. The sound began just (like in 'immediatly' almost) after I replaced the radiator.

The engine still has all of it's power, has normal temperature, no real oil consumption, etc.
The engine does need an oil and oil filter change I think.

My first thought is a bearing from a crankshaft tap/bottom conrod?


Any advice, thoughts? Anything is welcome now, I'm at the end of my latin here...


greetz,

matteus
 

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Without more information it’s hard to say. My guess is the bearing in fan clutch bearing bracket is the source or the idler pulley bearing. You should be able to isolate the noise with a stereoscope.
 

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Discussion Starter · #3 ·
ron in sc - 4/5/2006 7:38 PM

Without more information it’s hard to say. My guess is the bearing in fan clutch bearing bracket is the source or the idler pulley bearing. You should be able to isolate the noise with a stereoscope.
Yes I've used a stethoscoop to isolate the problem as much as possible. The thing is I can't seem to get close enough to the sound, as I think it is comming from inside the engine block.

I'll check the bearing of the fan clutch. Can you show me where I can find the idler pulley?

thx!
 

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Picture of fan clutch bracket.
http://www.mercedesshop.com/shopforum/attachment.php?attachmentid=30963&d=1137536681

Picture of idler pulley, put stethscope where red mark is.
http://www.mercedesshop.com/shopforum/attachment.php?attachmentid=30939&d=1137450580

Noise could be fan clutch too, however if your car has more than a 150K miles on it and the fan clutch bracket has never been changed that could be it.

Just to be clear when I'm talking about the fan clutch bracket I'm talking about the bearing in that bracket not any bearing inside the fan clutch.
 

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Discussion Starter · #5 ·
Thx! I'll take a look at it.
 

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Some of the common noises I experienced were:
- a buzzing sound because the aircleaner mounting bracket (mounted under the air cleaner and bolted to the cylinder head,) was cracked.
- when the intake hose connecting the air cleaner to the turbo (that U shaped hose) is loose or out of position the intake makes a roaring noise.

Just trying to help.
 

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Discussion Starter · #7 ·
I've listened again with the stethoscope. Although the 300D doesn't really look like in the pics (the fan clutch is mounted on the waterpump), I think the noise comes from the bearing in the waterpump (since it's the only bearing there).
How? It's a brand new waterpump. Does the bearing need lubrication of some kind?
Don't get it...


thx for the help so far guys!
 

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The photos I posted are of a 92 300E.

Maybe you could take the belt off and run car for a minute and see if the noise is present. At least you'll know it's not the engine if no noise.
 

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Discussion Starter · #9 ·
ron in sc - 4/5/2006 2:55 PM

The photos I posted are of a 92 300E.

Maybe you could take the belt off and run car for a minute and see if the noise is present. At least you'll know it's not the engine if no noise.
Hehe you read my mind! Just took off the belt and ran the engine. Noise was not present, so I am 100% certain it is the (front?) bearing of the waterpump. I still don't understand how this can be.
I'll see what happens next.
 

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Discussion Starter · #10 ·
ron in sc - 4/5/2006 2:55 PM

The photos I posted are of a 92 300E.

Maybe you could take the belt off and run car for a minute and see if the noise is present. At least you'll know it's not the engine if no noise.
Hehe you read my mind! Just took off the belt and ran the engine. Noise was not present, so I am 100% certain it is the (front?) bearing of the waterpump. I still don't understand how this can be.
I'll see what happens next.


Again, thx for the great help!
 

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put back the old water pump and the beld and then see what happens
 

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Discussion Starter · #12 ·
Problem solved!

Turned out the bearing of the tension roller was kaputt. Replaced the tension roll and the V-belt. Oh, so smooth now...[:D]
thx for all them great advices guys!

here's some pics taken during small repair. cleaned the front area at the same time with pressure washer (carefull ofcourse...[8)])





 

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i once had a similar problem but in my car it was just a lose plastic cover in the way of the fan and that made a similar noise to the one you described.
 

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i once had a similar problem but in my car it was just a lose plastic cover in the way of the fan and that made a similar noise to the one you described.
 
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