I just replaced the thermostat on my 81 sd because it was sticking open and running way too cool. It runs a lot hotter with the new t-stat, but I'm not too sure if its too hot or not. Before it never got over 90, even when going up mountains. Now it stays at 100 degrees or a little over pretty much all of the time. Could it be a bad thermostat? Is 100 in normal operating temp.?

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"spreading a trail of obnoxious where ever we go"
1981 300sd w/ 341,500 miles

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They should run about 80Cish. Mine did that as well, as soon as I replaced the t stat the temps would come up to almost 100C on the highway. As it starts to warm up over the next couple of months I will have to clean out the radiator.

Your radiator is clogged, either internaly or externaly.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

about the rad being plugged. before changing stat it ran cold.

did you check the degree of the stat? there are different ones floating around. also did you check it before installing in boiling water? not a bad idea to do.

also did you run and refill to be sure to get out the air from the system?

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Run and refill? I've never done that. Do you just add the coolant with the engine running?

__________________
"spreading a trail of obnoxious where ever we go"
1981 300sd w/ 341,500 miles

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Do you have to add coolant? Did you even drain the coolant to change the t stat?

Running the heater on high is all that should be needed for the system to burp itself. That and normal driving.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

Sounds like air in the system and/or a bad fan clutch. I FINALLY have the SDL running normal temps now, new M103 clutch , thermostat, and running coolant flush currently. Will be drained and refilled with Xerex this weekend.

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I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]

There could be an airlock in the system, it happened on our 83 when I ran it after all the work I did on it, pouring coolant into the upper radiator hose (disconnected from the radiator) till it was full, then quick reattaching it solved the issue.

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-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

Thanks I'll give that a try tomorrow morning.

__________________
"spreading a trail of obnoxious where ever we go"
1981 300sd w/ 341,500 miles

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