Noob Question--Cooling System
 

Alright guys, I hate being the new kid on the block but here goes:
I just inherited a mint cond '87 300E from it's original owner (my sister-in-law) because I am the only person she trusts to continue to give her beloved 300 the same care she always gave it, and she treated it right.
In the few days that I have been driving it I notice that the coolant temp guage reads right at 80c while in motion but when stopped at a long traffic light or a McDonalds drive through the reading will rise to around the 100c mark still well below the 120c redline but it still bothers me that the temp can fluctuate that much while sitting for a couple of minutes. Is this the nature of the beast or I'm thinking maybe an aux fan malfunction? My 3000GT and Sentra will hit operating temp and stay there all day. Any thoughts, observations, or horror stories would be greatly appreciated. As a side note, I never thought I could excited over anything with 4 doors but this Benz is incredible.

If the radiator is 20 years old & the coolant hasn't been flushed at least 5-6 times in the 20 years...I would start there. And a new thermostat is most likely needed as well.

The next time it reads that temperature, open the bonnet and check the fan.

If its not moving, then theres your problem.

All the above are correct. I had to replace the fan clutch on mine and did the thermostat for good measure.
Ed

Of course, the fan will still be moving, even with a bad clutch.

Thanks guys, I gave the aux fan blade a couple of turns manually (engine not running/cold engine) and I havn't had a problem since. I'll probably replace the aux fan motor before the hot weather gets here

i thnk he meant the auxiliary electric fan.

tom w

since they are pretty pricey and seldom fail, i would wait til it actually fails. i suspect it may have been stuck simply from sitting.

tom w

I think your car is ok.
 

Hi,

I think it is absolutely normal to see 80-90C while in motion (thermostat setting) and 100C when stoped in trafic or when the car is under high load like when driving up a hill in a hot day with the A/C working (aux. fans setting).

My car's thermostat opens at 87C and the aux fans turn on at 100C. I also was worried about that at the beggining because my other car keeps the temperature constant all day, but after replacing almost every component on the cooling system it keeps running like that and never gets overheated. Here we have 30-35C outside temp all year long.

If the temp gets close to 120C, then you have a problem but 100C-105C is normal in this cars. Just keep the coolant in good condition. Flush the system and replace it every 3 years.

if this is a noob question does this mean that you have a noob job? hehe (where were you on this one manny?)

it would reach "close to100" even under normal conditions if you stopped the engine after high load

no circulation = no heat dissipitation. Starting the engine from that hot temp and the temperature will immediately (almost) drop back to 90 ish. Same for idling actually so no big issue there as far as I can see.

Japanese vehicles have setup the temp gauge so that the needle stays in the same spot from 70ish C to 97C.....if you see it move you are pretty screwed already on a Japanese car. It would stay in the middle and rise up to the redline in absolutely no time at all.

good luck.