Low temp running 300SD

My '85 300SD runs cold, it goes up to 60C in highway driving but the temp stays almost at the bottom during city driving. After driving it for an hour on the highway, the engine (excluding exhaust)
is just warm, no problem touching head, and coolant is also just warm, is this cold driving harming the engine? Could it be that the thermostat is missing? Or should I not worry about this? Other than that, the car runs great, starts immediately, be it +15C or -15C
Thanks in advance, cp
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Either the thermostat is missing or it's bad and it should be fixed. Much of the wear on engines occurs when they are cold. It's likely taking a long time to even get up to 60 in your car, plus you'd have cabin heat a lot quicker, etc.
Don't know where it is on your 85, but if it's similar to mine, which is an 80 300SD it's real easy to fix. It's located in a housing right at the front top of the engine area with the two radiator hoses runnning to it. I changed mine in about 30 mins, they are avail on the internet for $15 or so.
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Thanks for the reply, do I have to drain the coolant first?
Thanks, cp
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Too cold, replace thermostat. Engine should operate at 80 degrees C.
Be sure arrow on new thermostat points upward.
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Will do, Thanks!

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I just replaced my thermostat and didn't notice an arrow (I wasn't looking) I placed the new one in the same direction as the old one. Assuming the old one was placed with an arrow going up, I could be 180 out. What are the consequences? Should I take it out and make sure the arrow is going up?

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Did you have to drain the coolant?
cp
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Of course he had to drain the radiator or there would be coolant all over the place when the thermostat housing was opened.
I believe the arrow orients a small vent hole. If the engine performs as it should I'd leave it alone and drive on!
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Got it! I thought there might be a trick, maybe plug something.
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Just what was in the housing and hose.

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Excellent, the coolant was replaced a month ago, it's such a purty color still that it'd be a shame to drain it all again.
thanks! cp
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