Knocking, Grinding, Squealing under the hood!!
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Joined: Aug 2005
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From: Seattle, WA
1992 300e
Knocking, Grinding, Squealing under the hood!!
Just started on the other day, can't tell if it's the tensioner or air pump. I mean it's F**king Loud, people turn to look and stare at me, waiting for a rod or something to come flying though the hood 
Then after a min or two it gets alot quieter, still noisey though, but for 25 ft, Not 300 ft. I am leaning toward the air pump, any way to test for sure, becides hose and long screwdrivers
Thanks to anyone who can help!!
Ron
Then after a min or two it gets alot quieter, still noisey though, but for 25 ft, Not 300 ft. I am leaning toward the air pump, any way to test for sure, becides hose and long screwdrivers
Thanks to anyone who can help!!
Ron
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Joined: Nov 2005
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1995 E320 Sedan 120K
I believe that I had the same problem. It was the air pump. I read somewhere that the air pump engages at startup for a minute or so to minimize exhaust gases. it then shuts off but the belt continues to spin the pulley. It looks like there is a double row of ball bearings supporting the pulley as it spins. If the bearing is gone, there is nothing you can do but replace the pulley or the pulley and air pump. To diagnose it I took a cheap stethoscope with an extension on it (tool store like harbor freight - cheap at 5.00 or so) and put it on the front of the air pump (obviouly can't put it on the pulley because its spinning) and REALLY HEARD IT! Internet parts stores will charge about $400.00+ for a rebuilt pump. I found one for $215.00 + 100.00 core. Superfast service (ordered weds at noon on the internet and had the part in Marysville, wa on FRiday. US mail!! see www.mbpumps.com After replacing it I did get a CEL but reset the light and hven't had any problems since. I will keep an eye on it though. Hope this helps. installing was pretty simple.
Thread Starter
Almost a Member!
Joined: Aug 2005
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From: Seattle, WA
1992 300e
rwogs, Thanks for the reply. I also read the pump works for a min or so during startup. I wonder if it is needed for emissions testing? If not I can remove the pump and get a shorter belt, saving lots of $$ in the process. I guess I need to ask a MB tech about it. I will report any info I find out.
Ron
Ron
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From: Seattle, WA
1992 300e
Good news, the air pump seems fine. I found the real problem, the fan clutch or the water pump shaft bearing. It is either loose or just plain toasted. The accy belt tension pulls it downward, when I move it back into place by hand then the fan should clear everything. I looked at it first and it looked fine at the time, but now the fan has wear spots on it from rubbing the pulleys as it rotates.
Time to search for repair info, anyone here replaced one and have any tips for me?
Ron
Time to search for repair info, anyone here replaced one and have any tips for me?
Ron
Last edited by TheDoughboy; Dec 2, 2005 at 11:41 PM. Reason: added text
Thread Starter
Almost a Member!
Joined: Aug 2005
Posts: 65
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From: Seattle, WA
1992 300e
Well after finding the Real problem it's fixed. My "fan clutch bearing bracket" needed replacing, the fan clutch itself was perfectly fine. The seal let loose and some ball bearings fell out causing the problem. So $65 for a used one and $15 for a pulley and all is quiet again. I did Not have to remove the radiator as some suggested, I had plenty of room to R&R it.
Ron
Ron
