1999 E300TD operating temperature
 

Does anyone know what the normal operating temp should be on a 1999 E300TD? Right now my car is operating about 80c without a/c and 90c with a/c on. The 90c seems a little high to me, especially since it hasn't even gotten very hot here yet. My coolant looks clean.

My '98 will creep up a little when it is warm out and the A/C is on but tops out at 90 when it is really hot out. You may have a problem with the aux fan or fan clutch if yours creeps up like that even if it is not that warm out but I would start by replacing the thermostat if yours is original or even if it is more than just a few years old.

They can get "lazy" and cause warm running conditions by not opening up far enough. It is the cheapest and easiest part of the cooling system to tackle, and you can do a coolant change at the same time (be sure to use only M-B or Zerex G50).

You can test the aux fan...Key to pos #2, hold both "auto" CCU buttons for 10 seconds. Fans should run at max speed.

Good luck!

Go to USER CP on menu bar and add your location and car to your signature so we know where you are.

Hot is relative. Its still 30 degrees in much of AK today, while in NorCal where I am its supposed to be 96 today.

I tried to update my signature, but I don't think it worked. Anyway 1999 E300TD Wilmington, NC. When I had the ac on and the temp gauge got up to 90c it was about 85F outside

Now its there.....at about 95C with your AC on the aux fans should come on in stop and go driving. I especially notice mine when I get off of the freeway and hit stop and go traffic. Jumps up in temp quickly. The next step is that your fan clutch will begin to lock up as it gets hotter. You'll know when that occurs as it will sound like a 747 at lower RPM's.

I think you need to wait until it hits 95C to determine if there is an issue or not.