Quote:
Originally posted by Rafi
most responders say that is how it should be. The part I do not understand is why is the temperature going up and down so much ~85 to ~100 driving vs idleing, why isn't the thermostat and all other components doing their job and maintaining a constant engine temperature. I also do see a yo yo effect after my water pump started leaking, before changing the water pump I do not think I saw that or I did not pay close attention. Before anyone says I need a new thermostat, This is my third theromstat after the water pump change.
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Where is the "requirement" to maintain constant temperature? It's not Mercedes or any other OE as most cooling systems are set up similarly.
The thermostat begins to open at 87 plus or minus a few degrees tolerance. In mild weather at freeway speed it should not run more than 90 on the gage, but you get into traffic with no air flow through the radiator and the temperature rises. At 100C the fan clutch tightens and increases air flow through the radiator. If the temp still rises to about 105 the electric fans engage at high speed and quickly cool the engine. As long as you are in stop and go driving without the A/C on this cycle will continue.
The C5 Corvette guys have the same complaint. The only fans are electric and without the A/C on they don't engage until 227F, but at freeway cruise the coolant temp usually runs 190-195F.
The job of the cooling system is to maintain the coolant temperature in an acceptable range, not a constant value, and the normal range for the wide range of driving conditions is about 85 - 105C.
Duke