High idle in park over heat in park.

when I put it in drive car starts to cool down drive it around the block and it's temp lowers below 80 and stays there.

put it in park it take about a min, and the rpms creap to a little over 2k and the car starts to over heat.

could this be the fan clutch?

Where is the temperature gauge needle sitting at?

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1989 300CE

when I am driving the needle is sitting at a litle above 80 id say about 90.
when in park the rpms slowly increase to a little over 2k and stay there temp climbs into the red 120 zone.

when the car gets hot i put it in drive after a block or so the engine cools down.

(i'm thinking this is a related problem to the very hard starts after sitting over night or through my 12 hr work shift. when the car does turn over it roughidles and dies untill the car warms for 3-10 seconds)

For the high idle I would start off by checking for vacuum leaks. On the M103 the idle air control valve hoses tend to get brittle and crack with age. You could also remove the idle air control valve to clean and inspect it. It could very well be sticking open. As far as the overheating you can start off by checking the coolant condition, level and for any leaks. Since the car runs okay when moving I would suspect possibly a bad radiator or water pump, especially if they are original. Do you know if the car has factory or aftermarket (generic) coolant?

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1989 300CE

The car started doing this recently I was at Auto Zone picking up some bulbs and i noticed. water under the car (left it idling when i ran into the store) temp was high so i replaced the thermostat there at auto zone and just added water.

If the coolant is green, pink or orange it is the wrong fluid. You can only use either Mercedes-Benz fluid or Zerex G-05. Prolonged use of other fluids may cause problems in the coolant system. Sounds like the car is loosing coolant. You will have to locate the source(s) of the leak. Can you roughly determine where the coolant was leaking from?

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1989 300CE

the cap was off of the coolant fill jug the day i replaced the thermostat.

when the car idles high in park the engine get really hot. but only in park does the engine idle high.

i just ordered a new coolant temp sensor and ovp relay

My guess is a non-operational fan clutch.

Also dont topp off the expansion tank, only fill to top seam and burp the system. The tank siphons back and fourth into the overflow tank/reservoir in the fender. If you topp off the system it will get warm and always popp the cap and let coolant out. Find a owners manual or do a search here or at benzworld to see what I mean.