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Old 07-26-2003, 01:29 AM
zam2000 zam2000 is offline
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Join Date: Mar 2003
Posts: 29
Unhappy Need help with overheat problem

In the last few days, my engine temperature has been running about 15 degree hoter than before (even though the weather has cool down a bit). Before, even with the triple digit temperature outside, and my AC always on, the engine temperature never go pass 100 (and stay around 80 most the time). Now, with the AC on, when I cruise on the freeway, temperature stay around 85. However, once I stop, or with stop-and-go traffic, the temperature shoot to 100, or pass it.

Further exame of the engine, I notice that the auxiliary fans run at much lower speed. Before, with the AC one, the fan run at low speed, and then once a while, I would see the aux fan run really fast (and loud) for few minutes, then stop, then run again .... (I guess it runs as the temperature rise, and stop when detect cool down). Now, it still runs and stop, but it runs at much lower speed, and much quieter, almost not detectable if you don't open up the hood. With the AC on, and the car at idle, I don't see that fast & powerful running from the aux fan again. Because of this (low speed fan), the fan constantly repeat running for a minute or two, then stop, then run. Also, with the AC on and the car at idle, the engine temperature shoot pass 100, which never happen before.

I've tried to replace the relay (behind the fuse box). Is this car has only one relay for the fan ?, since that's all we found. As some has recommend, I has also disconnect the sensor on top of the thermostat. Nevertheless, I don't detect any improvement. The aux fan still only run at low speed.

My mechanic recommend to replace the entire aux fan system next. He says the fan suppose to have two speeds, and that the high speed for my fan is dead. I don't know if this is true. Since to me, the fan has only one motor, and it's either run at high speed w/ high voltage (or current) supplied, or low speed with low voltage (or current) supplied. If the motor is dead, the fan would not run at all. After all, this's an electric fan. Is my logic correct ???. Beside, the cost of this aux fan work would be costly (~$500), so I'm hesitate to commit large amount of money into it (given my current situation, and not sure if that would cure the problem).

Is there something else that I'm missing. Is there some other test that I sould be conducting in my car ?
My car is a 98 E320. If you have experience dealing with similar like this, would you please let me know. Since I don't know much about Benz, when you give me your advice, can you pls provide location (in the car) of the part that I should be looking at ? .

Thanks so much.

Last edited by zam2000; 07-26-2003 at 11:08 AM.
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