Mine runs pretty consistant at 80-85. Winter temps in the low 20's (f) and high temps last fall of almost 100(f). All highway at above the legal limit by about 5-10 MPH all the time. Never over 90 on the temperature even with the AC on.

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Habits I support
95 E300 D 220,000 & counting (I think I'll call him Fritz)
02 Tahoe (Momma's ride)
98 GMC Sierra 120,000
57 Chevy Nomad (bought in '69)

The 350SD had trouble breaking past 90 degrees at any one time. The twin auxiliaries never had to work all that hard, either.

The 300SDL does not like WOT for extended periods. It will generally warm up to 83 degrees and stay there. However, if I lay on the pedal, I can easily get it up to 110.....Yikes.

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1987 300SDL (324000)

1986 Porsche 951 (944 Turbo) (166000)

1978 Porsche 924 (99000)

1996 Nissan Pathfinder R50 (201000)

80 deg. Celsius year round, no matter what driving conditions. But I know my cooling system is in perfect order. Within the past year she's had a new water pump, radiator, viscous fan and two flushes with MB coolant. This is the '83 300SD.

You might say I live by the overkill rule for engine maintenance.

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Regards,
Aaron

http://www.swag.de/medien/pdf/elektrik/pdf/thermofuehler.pdf
http://www.kienzle.de/uploads/media/sensoren_instrumentierung.pdf
page 18.
@ 90 Celsius the sensor should read 51.2 (+/- 4.3) ohm resistance.

78-82 degrees. After the t-stat mod if runs perfect.

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1981 300D 147k
1998 VW Jetta Tdi 320k
2001 Dodge Ram 2500 141k
1979 300D 234k (sold)
1984 300D "Astor" 262k(sold)
Mercedes How-To and Repair Pictorials
I love the smell of diesel smoke in my hair

hey guys i have a problem we recently got my moms 82 300d turbo on the road from sitting for about a year and now the temp gets really high on the highway past the 100 mark and i changed the thermostat any thoughts? I think it may be a blocked passage somewhere or something because around town it stays at 80 only when your on the highway does the temp get up there.

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1982 300D Turbo (Mom's)
1993 BMW 525I (Dad's)
2001 Vw Golf (Brothers)
2002 Nissan Ser SpecV (Im the Black sheep lol)

My sd runs about 85c, when the heater is on full blast she will drop to about 75. if i am running on a steep grade or loaded down she will get up to about 90.

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81' 300SD AKA "Big Helga"
84' 300D Euro spec (Veronika)
85' 300D NonCalifornia (Heidi)

"We shall not fail or falter; we shall not weaken or tire...Give us the tools and we will finish the job."
-Winston Churchill, 1941

"I'll have a Chinchilla!"

If you are seeing 110 I suspect your radiator is in need of de-calcification or the water pump might be getting corroded (ask gsxr what a corroded wp impellor look like!).
My 603's (124 chassis) never run that hot unless I am driving up a long uphill slope on a really hot day with WOT. On the straightaway I've never see anything over 100 even at 105 MPH in the summer and that wasn't quite flat out

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'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!

Usually 90C around town in cool weather, have seen as high as 102-105C on the highway when pushing it hard(AC doesn't seem to affect it much), usually right around 100C when running on the highway at reasonable speeds-BTW am still getting 27-28 hiway MPG consisently (I must be one of the lucky ones! ). Some people have theorized that running a little hot raises MPG and maybe even helps burn off excess carbon. I have a new Nissens radiator and Zerex GO5 antifreeze.

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1982 300DT 190K (Diesel Purge + synthetic oil=smoothness at last!!!)
2004 Ford E-350 6.0 L PSD 227K
2006 Dodge Ram 3500 SRW HO Cummins 4X4 48RE 42K (brute force tow vehicle)
2005 Scion xB wife's rolling pop can
1993 GMC Sierra C3500 6.2 142K

Mine takes a while to get up to 60 and only gets up to 80 after being on the highway for a while. It got over 80 one time but that was when I was driving up Mary's Peak, which is fairly steep.

I'm thinking my T-stat is bad and this is why I get no heat, except for about a minute or so when I turn it on and the car has been driven at least 20 minutes. Any thoughts?

This is my 100th post, btw. Hooray for me!

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Ralph

1985 300D Turbo, CA model
248,650 miles and counting...

boiling on up hill at any time and spiting antifreeze, took it to a radiator shop to have the radiator rod cleaned the guy just inspected the rad cap and told me to buy a new radiator cap that one the car had had a "hairline crack" at the rubber ring and that was the problem I was not too convinced but I follow his advice and like magic the temp never goes over 80c even on hills, there still honest people in this world, obviously I will be back to his shop if I ever need to fix a radiator.

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2000 430 ML
2005 S500
87 300 D
61 300 restoring

Congrats on the 100th post BTW,
Your thermostat is very likely stuck open. Diesels last longer if the thermostat works properly. A cold running diesel to me is worse than a hot running one. It should run up to 83 or so fairly quickly when its being driven under load (the iron head engines take much longer to get to operating temp than engines with aluminum heads)
Heat won't come on until you see about 80C on the temp gauge

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'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!

Thanks for that advice, dieseldiehard. I guess I will change it sooner rather than later. And also, I looked at the coolant today for the first time since buying the car; it's green! Suppose I should have checked on that earlier...

I guess I'll flush the coolant and change the t-stat at the same time.

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Ralph

1985 300D Turbo, CA model
248,650 miles and counting...

Before changing the thermostat, mine would rarely cross 60 C. Afterward, it gradually works its way up to 95 C. Hard driving will put it up to about 105, but my temp gauge sometimes behaves erratically and I strongly suspect it is reading high.

My heat starts to blow (cold air) when the gauge is just over 40 C. I get good heat on the low blower setting after the gauge passes 60. The high blower setting blows hot air for about 30 seconds before going cold. I think my monovalve is on the way out. Mein Klimaalange funktioniert nicht (AC no worky).

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Whoever said there's nothing more expensive than a cheap Mercedes never had a cheap Jaguar.

83 300D Turbo with manual conversion, early W126 vented front rotors and H4 headlights 400,xxx miles
08 Suzuki GSX-R600 M4 Slip-on 22,xxx miles
88 Jaguar XJS V12 94,xxx miles. Work in progress.

I am a newbie to the MB in general, but I love mine.
I only recently started driving my car, but since I flushed the radiator and engine block, and filled it up with a good mix, my car (275K) heats up to approx 80 within about 6 or so minutes. on the highway (about 70-80MPH) it will climb a smidge above the 80 mark, but it has not really gotten hot here in NC yet, (although yesterday's brush with 89 oF is starting to look warm) so I don't know where it will settle on a hot day. I have not gotten the A/C working yet either, so we will see where she sits with the A/C going soon. (hopefully!)
I can usually get very good heat within about 5 minutes and then REALLY good heat, I usually have to turn it down or off before I get to work at about the 15 minute mark but then again, this winter was unusually warm it never really got cold here this year
John