I am a longtime lurker, but have not posted much. I have learned a great deal about my car here, and don't recall this particular question raised, so i hope someone can help me determine the answer.
I have a 1997 C36, with 102,000miles. Recently my engine appears to be running warmer than usual.
Now I know there is debate on what is considered 'normal" engine temp for a MB, so i suppose this is based upon personal experience for the car.
For my car, i recal the hottest it ran is not more than 90 degrees. Typically 80-82 degrees in city driving, with a slight rise to 84...but would soon cool back down to 81 or 82. Basically the needle would not move past the half-way mark between 80 and 100. Usually at the middle or between middle and 80.
On the freeway, the engine usually ran no hotter than 82 degrees. When stopped from a half-hour drive on the freeway, the car would rise to about 85-ish, then drop down to 82.
At idle, the engine would slowly fluctuate from 84-82...so it appeared to be the result of the cooling system working.
Lately I notice the engine staying more towards 85 and 90 degrees at idle.
On the freeway the needle stays around 85- 83degrees.
Recently, the needle shot up to 120 once I stopped after a 1 hour drive from the freeway (drove around 80-90mph). During that time the needle was at 100 degrees while driving....
When i got out of the car with the engine running, the fans were on full blast. I turned off the engine at 120 and let it cool. I checked the engine bay and the coolant resivor was full. Oil was ok.
Fans were screeming when I turned the engine back on 15 mins later. Engine temp was 115.
Towed the car back to my mechanic and he found the thermostat faulty, so he replaced that. He did not find any other cooling system problems.
Now the car is not overheating, but is still running around 91- 85 consistently.
I would like to know if this is "normal" or a symptom of other issues I need to investigate.
Because my engine ran cooler before, i know the car is not running as it used to.
Rgearding the last time I had my coolant flushed, it was approx 4 months ago from the dealership. I do remember the car running a tad warmer than usual afterwards, but did not think about that much until these recent overheating issues.
I read this thread: Thermostat
And thought it was very informative, but I thought it was odd for a w202 to run 90-100 degrees and consider it "normal"!
So that's why i'm not sure what is "normal" for my car.
If this is still within normal operating temperatures, is there anything else I can do to cool the engine further? I read biasing the ratio in favor of more water than coolant helps for example...
Anything else that can be done?
I suppose I consider "normal" to be no hotter than 85 degrees on a hot summer day with AC, or after driving the car hard. Otherwise the car was almost even with 80 during light driving or on a cool day on the freeway. My car used to be this way.
Any advice on how to troubleshoot this is much appreciated. Also, any feedback on what is "normal" engine temperature for my car is also appreciated.