temp instantly spikes when climbing hills - Page 2 - PeachParts Mercedes-Benz Forum

ah-kay · #16 06-21-2010, 01:54 PM

I just fixed my overheating problem with my 300SDL but it may or may be applicable to your car.

1) Change out the overflow tank cap with a new one. I bought a 20lbs one from Autozone for $5, so it is not that expensive to try. Try to sqeeze the radiator hose after the car is at temp for a while. The hose should be pressurized and should stay pressurized for a day, may be longer. This is normal. If the hose is not pressurized then the cooling system is not air tight, most likely a leaky cap.

2) Check the aux fan can go on high speed. I do not know your car but there should be a thermostat-switch near the top of the radiator hose. It may be 2 prongs or may be 3 prongs. That is the trigger switch for the fan to come on. On my 300SDL, it is 3 prongs and if I shorted the 2 prongs connector and the fan will come on. The third prong goes to a single connector is cut in at 125/8C to turn off the A/C I think. Your car may DIFFER.

3) You can get a lower cut-in temperature thermostat switch. My 300SDL is 105C rated ( grey color ) for the fan to cut in. I bought a 100C rated ( red color ) to give it a better safety margin as it has the #14 head.

Hope this help. Good luck.

babymog · #17 06-21-2010, 01:54 PM

Same thing on many domestic/American makes. The oil pressure "gauge" for example, pops to the same place in the normal range, if the oil pressure is normal, no fluctuation.

BMW figured this out in the late '70s/early '80s also. Customers would get together at club meets etc., notice that one car had higher or lower pressure than another, the guy with the lower pressure reading would start to badger the dealer for a repair. Changing to the idiot gauges solved the "problem".