Picture of a very bad thermostat.
1985 300SD.

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What symptomology did the patient present?

Elevated temperature on the way to work = 99C, with ambient of 40F.

She is normally rock solid at (winter) 80C - (summer) 90C.

We just started up the 83 tonight after finally completing the project!!!!

It started in 2 cranks after a 5 second glow, battery nor engine had been used in over 2.5 months! Awesome. Hoooowever, to get to the point of this post, the engine temp rose, rose, rose, rose, all the way to 92C, then I shut it down, the upper radiator hose is empty/no pressure/temperature, everything is staying in the engine/Heating system....

The heating in the car works great, nice and hot, but the thermostat seems to be a no-go-no-open....it used to work fine, did leaving it sit like that get it stuck? I hit it with a rubber mallet a good number of times, to no avail. Next step I am sticking a screwdriver down into it from the top port to see if I can knock it loose.

Next problem, blower is on its last legs, its making grinding sounds, but still moves air ok....sigh.

Any tips on getting it loose/flowing again? In about 25-30 mins I am going to go try prying at it, but if that doesn't work I dunno what to do other than replace it. We'd rather not have to buy both a thermostat AND blower...that'd stink big time.

__________________
-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)

Those thermostats are so dang cheap, just replace it! It isn't worth messing with. I don't know what Fastlane charges, but I know that *************** has em dirt cheap.

Also, could your blower motor just have bad brushes?

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stat in with the disc toward the engine, right?

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.

Thermostat direction picture

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Was the cooling system opened during this three month hiatus? Drained for any reason?

We drained the system entirely so we could disconnect all the climate control hoses, the system was open at the little return pipe from the aux pump, the output port on the side of the engine, and the drain plug was out the whole time. I refilled it with MB coolant, the thermostat just seems to be stuck. If we can't get it to reliably open we'll probably just replace it....
As for the blower, not sure if its just the brushes, it sounds bad, like mine did when it went in my car. It bogs down and does bad noises. The whole motor is probably toast. The motor from my car was, it was burned and all loose and falling apart, brushes were almost flat....very sad. Ebay has them for $130 though, and I used one of those, they work fine.

__________________
-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)

As you noted on the other thread, the system has air entrapped. The thermostat is almost certainly not the culprit here. A thermostat does not go bad because you decided to replace the stabilizer bar. The SD sat for five months with the cooling system open and the thermostat didn't care one bit.


As noted on the other thread, remove the upper radiator hose, fill the head and the hose with coolant and reconnect the hose, losing as little coolant as possible.

Also, as noted by Raymond, there is a small bypass tube between the head and the water pump on the front of the engine. Make sure that it is flowing coolant properly. You'll need new aluminum crush washers, most likely, if you remove it.

I'm just about to dive in and replace mine. Which way is the arrow stamped on it supposed to point? Also It looks like I got the wrong thermostat kit from fastlane. I have the later style horizontal thermostat housing, and I got a kit for the vertical style housing with a round seal. Are the thermostats the same, and can I re-use the old seal? I doubt I can get one locally and I want to get this project done while there is a break in the rain.

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1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine

the gaskets before, i think. if it seems suspect you can add a little silicone around it. use sparingly.

tom w

__________________
[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.