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Old 08-02-2006, 05:05 PM
Registered User
Join Date: Jul 2006
Posts: 4
350 sdl temp

91 350 sdl, normal temp range approx. 80-85c In traffic or slowing down from highway temp spikes to appox 100c + midway between 100 and 120.

Is this normal, as temp will go down once moving 20mph or better, Worried about overheating, radiator, clutch fan etc seem OK.

Had same isuues with 83 300sd previous.

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Old 08-02-2006, 06:15 PM
jrgslg's Avatar
1985 300sd
Join Date: Jul 2000
Location: Eads TN
Posts: 217
When I first got my 350sd after reading the overheating horror stories.I installed a new clutch fan,waterpump and thermostat.I also installed aftermarket high performance a/c fans and installed MBZ antifreeze.My 350sd never gets hot,I think in the long run it was money well spent.Good luck Johnny
85 300sd SOLD ,85 745i,95 740i,1972 Suburban,1938 International
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Old 08-02-2006, 06:18 PM
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Location: Loganville/Atlanta
Posts: 2,156
Looking at many an old MB I think the clutch fans are alot to blame. You said it was ok, how did you check it?
1981 300D 147k
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1979 300D 234k (sold)
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Old 10-12-2006, 09:12 PM
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Running Used Cooking Oil
Join Date: Nov 2005
Location: Providence, RI
Posts: 37
Since I changed the theromstat on my 350SDL, it runs consistantly just slightly above 80 C.

On hot days, just add a few degrees, but not much.

before I chenge the thermostat, it ran cold, always under 80C
Providence, RI
Current Fleet:
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Old 10-12-2006, 10:41 PM
Blevinsax's Avatar
'91 350SD GreaseCar
Join Date: Jun 2006
Location: Las Vegas, NV
Posts: 480
Exclamation That's too hot - you should have it taken care of ASAP.

Based upon my experience with the exact same issues on my '91 350SD and the advice given to me by the gracious folks here at the forum, those temperatures are definitely too hot - you run the risk of overheating and warping the aluminum head and then wrecking the motor; something you definitely want to avoid with these 3.5L's since they are already prone to rod bending.

I also just replaced both auxiliary fans up front, fan clutch, thermostat and refilled with MB Coolant. Now it consistently runs right around 80C - slightly above with A/C and slightly below without A/C.

I also agree that it was money well spent and would definitely recommend it.
1991 350SD 276,000 miles
2001 VW Beetle TDI 115,000 miles

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Old 10-12-2006, 10:49 PM
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smoke gets in your eyes
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Location: SF Bay Area
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Don't forget to clean the air passages in radiator and AC condenser. Easy enough to pull the radiator and use air or water to blow bugs and dirt out of the air passages. With the radiator out, you can clean the condenser the same way. There is coolant flowing around the engine bay but these engines are no less dependent on air for cooling than a 25hp Beetle

93 300SD
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Old 10-12-2006, 11:35 PM
Registered User
Join Date: Aug 2005
Posts: 34
oh my god! Hommie!

howdy partner, i currently own 3 diesels , if you get the thermo, that are 80 and under youll keep the alum. head good till 500,000 if not prepare for chingy! sometimes a good thing to do is water pump and fan and tensioner pulley at the same time, and spray out radaitor espically if it is a older high mileage benz and flush that bad boy if the water gets to large a ph it will also eat though the head.

good luck, just turned over 418,000 on my 86 sdl.

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