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Old 09-15-2008, 03:24 PM
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Join Date: Jun 2006
Posts: 109
82 300SD engine knock at IDLE only..??

i was checking out this 82 300SD for purchase but it had slight, not very loud engine knock at idle. If RPM increased, dissapeard. Didn't dissapeard with engine warming up.
What it can be??
Thank you

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Old 09-15-2008, 04:14 PM
tyl604's Avatar
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Join Date: Feb 2008
Location: Atlanta, GA
Posts: 3,235
Might be the air filter housing not tied down properly.
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Old 09-24-2008, 12:37 AM
dieselnutnj's Avatar
Join Date: Jul 2008
Location: Newton NJ
Posts: 163
look for broken rubber mounts or the metal mount itself. If that is not it.. I would look at either injector nailing *bad injector or spray pattern makes for a wierd combustion sound* or look at your oil pressure Idling. How many miles on it? Does the knock appear when it's hot or cold or at any time? You should have a minimum of .5 bar or 7.5 lbs of oil pressure when engine is warm and idling. Keep us posted.

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Old 09-24-2008, 11:08 AM
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Join Date: Jul 2006
Posts: 8
If the oil pressure is uneven at idle, I mean if it looks like the oil pressure guage is rocking with the engine. It's just starting to spin a rod bearing...

Spoken from expreience.
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Old 09-24-2008, 11:39 AM
Actros617's Avatar
Ich fahre dieseltypen
Join Date: Apr 2008
Location: Oklahoma
Posts: 1,121
It should be the injector either needs to have a diesel purge or replacement is required, i too had the same problem but with a 300SDL and sloved it by replacing the injector.
Benz's in our garage
1994 S350 357k mi

1987 300SDL 200K+
1994 S320 181K mi
2008 E320 Bluetec 127k mi
1999 S420 130K mi
1980 240D 360k mi


1995 E320 Special Edition [Rear ended]
1984 300SD [Head on collision]
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Old 09-24-2008, 11:57 AM
rrgrassi's Avatar
mmmmmm Diesel...
Join Date: Jun 2006
Location: Royse City Tx
Posts: 4,872
A jumpy oil pressure guage can also be caused by failing o-rings on the oil filter lid shaft. Also check the alternator and the vacuum pump for noises.

70's SPM #5608 Fairmont A-4 MOW car

06 VW Jetta TDI 210K miles

03 VW Golf TDI 5 speed 372K Miles

RIP--Lost in fire...82 300D 322K was My Daily Driver-On the search for a w126 now...

90 Dodge D250 5.9 Cummins/5 speed. 350K
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Old 09-24-2008, 05:59 PM
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Join Date: Nov 2007
Location: Cameron Park CA
Posts: 1,863
from my experience with sd's the exhaust pipe follows very close to the car under the passenger side footwell. Mine knocks on the chassis sometimes at idle and is very annoying.

1981 300SD 512k OM603

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