My 1980 240D manual is running a little hot
About 95-100
I recently changed the water pump
Could this be a thermostat thing (do they fail open or closed)

what elese could it be?

double check to make sure that all the air got out and it is topped up, park uphill run the heaters with the cap off.

also could be thermostat easy 10 dollar swap though

A recent thread discussed this in greater detail, but I'll spew the abridged version.

Recently, a lot of people have been stating that their cars have been running hotter following a replacement of the thermostat, water pump, or both. I was initially concerned with this, but I see no adverse performance differences since the change. With a new thermostat, I don't think it's uncommon for the car to be running around 95C. I would just drive it as it is for now and keep an eye on the temperature. From my experience, I've pushed my 300D on the highway pretty hard at 80-85 mph and it never went a hair above 95C. Now as the warmer months come along, we'll see how she does with the AC compressor running, but I'm not putting a whole lot of worrying into it at this point. Just keep driving and if it gets well into the 100C range, then I would change out the thermostat, no question.

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Never be ashamed to ask for help.

1985 300D
1987 300SDL
1970 Jaguar E-Type OTS
2002 Dodge Intrepid (Traded In)
2011 Ford Crown Victoria

I only start worrying when it gets above 115C. Of course I live in the desert and drive 75mph when it's 110+F outside.

That's another reason I'm doing the York2Sanden compressor swap next month.

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2013 Volkswagen Jetta Hybrid SEL Premium (Sparky)
http://badges.fuelly.com/images/smallsig-us/193500.png

It's a car not a science experiment! Open the throttle!

u can buy a laser thermometer for 20-30 ish, just beam all over the rad and her surrounding area,
if not u can use your pinky puppy paws aka fingers to fell around, esp the rad quite often is partially plugged.
When u feel the rad, u may feel hot/warm area is not consistent, some area is stone cold whereas some surface is scalding hot.
The reason is u got partially blocked rad, perhaps heed a quad or triple bypass.
1st thing is run a garden hose into the rad hose, see if can flush it out, or buy a can of rad flush,
simple approach always save u mulla.
Who doesnt know to keep putting new parts into your panzerwagen, if u have very deep pocket then nothing is impossible.
God bless & good luck

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Mercedes released a Bulletin many moons ago saying......"If the coolant does not puke out of the system and returns to normal temperature back on the road, no remedial action required."...or something to that effect.

People were bugging Mercedes about the needle hitting RED section in traffic and drive thru's.


.

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"A liberal is someone who feels they owe a great debt to their fellow man, which debt he proposes to pay off with your money."

If I'm on the freeway from 65-75 mph with ambient 75-80F temps. The needle is just above 80C to about 90C.

If I push speeds up to 80-85mph, the needle climbs to 95F to just under 100C.

If the coolant is the least bit low, the temp climbs much higher, more quickly. If the cooling system doesn't hold pressure (leaky cap or hose/connector/valve leaks) the effect is more pronounced.

Run a flush and check your cap.

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2013 Volkswagen Jetta Hybrid SEL Premium (Sparky)
http://badges.fuelly.com/images/smallsig-us/193500.png

It's a car not a science experiment! Open the throttle!