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Old 01-22-2000, 07:08 PM
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I got a lot of good suggestions from my last post (1-16-00), but I still have the high temp problem. Up until 3 weeks ago, the temp in my 85 300D (202,650) never rose above 95* (in Summer with A/C on). Now it is running 85*-90* with heat on and up to 100* with heat off.

This is what I've done in the past week>>>

1. Replaced thermostat with 80* MB OEM unit (installed with arrow up!)
2. Replaced Expansion tank cap.
3. Flushed system 3 times
4. Replaced Radiator today with brand new radiator (not a rebuild).

I also replaced the expansion tank and water pump about 9 months ago.

Even with the new radiator, the car is still running a good 10*C hotter than it did only three weeks ago. I feel I just wasted $ on a new radiator as I am seeing no temp improvement over the old radiator.

While flushing the system, I did so with the thermostat out. After 35 minutes, the temp never got above 50*C and the defrost was barely blowing warm.


1. Could it be a bad thermostat (even though I just replaced it)
2. Could it be a bad waterpump that is not showing visible or audible signs of wear. (I never have felt a surge when squeezing the upper hose at operating temp)
3. Could it be a bad temp sensor? (how do I troubleshoot?)
4. Is it gremlins?

Thanks so much for replying with suggestions.
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Old 01-22-2000, 07:49 PM
Registered User
Join Date: Mar 1999
Location: Suwanee, GA, USA
Posts: 4,712
As you have found, this is a hard one. You could have a bad gauge and or sender. You easily could have a faulty new thermostat. New doesn't mean good. There is an arrow on the thermostat that has to be clocked a certain direction. The other thing is that more than one degree of thermostat is available for your engine. Are you sure that you have the correct one.?

1981 280GE SWB
1987 16V

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Old 01-23-2000, 06:37 AM
Join Date: Jun 1999
Location: Quezon City, Philippines
Posts: 79
Does your car have a thermally activated cooling fan? It could be slipping or sleeping.

And yes, audit your temp gauge and sender.

Did you replace the cooling system components simultaneously, or one at a time?
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