I recently performed 30,000 mile maint on my 85 300D. That included oil to to the radiator drain and thermostat replacement with mercedes theremostat. I drove it 2 miles and the temp gauge rose quickly and it got to 120, I stopped, waited, added water to top off, and drove the way home. It did it again!!! so I cylcled the heat and got it to stay around 100 degrees C. What is normal operating temp, prior to the stat change it stayed around 80 C. I dont want to drill holes in it because prior to this it had no problems with temp.

Air bubble. Try filling from the top radiator hose.

how do I get the air bubbles that are in, out?

Park the car with the nose pointing up a slope and fill from the top radiator hose.

so is that the tank to the left of the radiator. I let it run without the cap off and added water. What temp is normal for a 85 300D

Your new thermostat should have a temp rating stamped in it. Probably around 80C. If it is 90C then it will run hotter than it did before. Check to see what your new one is rated at and if you are unhappy get one which matches your old one. I would run an 80C in it if it were mine. It is also possible that your new thermostat is defective if it constantly runs hotter than rated (assuming you got all of the air out of the cooling system). In that case the only cure is to replace it again with another new one.

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Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz