Will High Running Temps "hurt" a Motor???
 

Hello all, for about a year, my 85 300D ran its coolant temp anywhere from the "80" on the guage to right below (or sometimes at) the hash mark above (I think its "100"). It would vary depending upon the day, the temp and my right foot... Well, I am pleased to say that I got my radiator flushed, and new thermostats installed... Now she runs right above the "80" and no matter what I do to her, she won't move above! Great, so I'm running cooler, but did I harm my engine running it hotter??? Was damage done/life reduced having a hotter running mill??? Thoughts/adivce is greatly appreciated.... Thanks!

Thermostat is a Key Item
 

It seems to me that, everything else operating properly, the thermostat will determine at what temperature your car will stabilize. Since you changed the thermostat, you may have gotten one with a lower temperature specification, thus the lower running temperature.

My 1982 300D tends to run about two "needle widths" below the 100 degree mark most of the time. During hot weather with the AC on it will exceed that a bit. So, I don't think you did any damage to the engine by running at 100 degrees, if everything else in your cooling system was operating OK.

I'd probably like to run a little cooler, like yours is doing. It especially sounds good that there is no change during harder conditions. Flushing your radiator probably did you some good.

Where did you get the thermostat, and do you remember if it had a temperature rating?

Will be interesting to hear from others where their 617 engines run on temperature. Also, I would guess that the in-dash temperature indicator isn't exactly instrument-quality in accuracy, so there might be some variation among cars depending on variations in the temperature sensor, the gauge, and the interconnecting wire condition.

Ken

Thanks for the reply... I'm glad that my car used to run like yours, because to be honeset, they all run like yours. Mine is the exception now... I can remember my father having an 85 300 when it was only 5 years old and it ran like yours.

Had no idea the thermostats varied, mine came from the dealer, whichever they put in... At this stage of the game, its hard to get accuracy out of these cars. Each one has evolved into its own identity, with their aging and tolerances varying, its hard to get a text book reading from a 20 year old VDO guage. Even if your car is 17 year old, some of the parts may be older! Don't forget these cars when made in a day before "Just In Time" techniques were a standard.

I cured a high temp problem by removing and cleaning out the fins of the radiator. If it has never been done I am sure it is due. I used a pressure washer to blow all that crud out of it. Some folks say not to use a pressure washer as it may damage the fins. I did not damage the fins but it is something to consider.


good luck

bob

The immediate problem with higher coolant temperatures are the potential loss of coolant over time. 100C is just boiling, and under pressure is a few degrees from actually boiling.

Your oil will run closer to 125-150C when normal, and easily boils off any condensation.

Running 5-10C 'hotter' is not a big deal, and didn't damage the engine. Just keep checking that coolant flow, level, etc. Sounds like you've done exactly the right thing with flush and thermostats. 'Way to DIY!!!

BCingU, Jim

I just replaced my radiator this afternoon. The temperature runs between the number 8 and the second (100 degree) mark on the gauge. Tonight, in 70 degree temperatures, the top half of the 8 on the gauge was covered by the arrow. Considering this is a brand new radiator with the apporpriate 82 degree thermostat (which is also new), I'm just going to take it that this is the correct temperature and gauge reading for my car.

Greg
'84 300D

what about the other way?
 

I just changed my thermostat, thinking my 240D was running to cold.
But nothing really changed, other than the local foreign parts fellow not furnishing me with the right gasket, me using the old one and having a tiny leak now.
Anyway my car runs with air on at all times even at 100 degrees F outside always around 60-70 Celsius.
Is that normal? What will it do in winter?

Thanks, Wolfgang

"engine will always be 3-10 degs higher than your t-stat is rated at" per Steve in the following link:

http://www.peachparts.com/shopforum/tech-help/6968-1991-560sel-temparature-problem.html?highlight=tstat

David

On your 240D - it sounds like you installed the wrong t-stat. I think they are all supposed to be 82 degree thermostats. Running too cold will cause poor cabin heat in the winter and overall make your car inefficient (use more fuel, more black smoke). They are desinged to operate at a certain temperature.

Greg

Low temp. thermostat
 

Thanks, I will have to install another thermostat before it gets cooler here in hot land.:cool: