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Welcome to thermodynamics Posted by Ari [Email] ![]() ![]() In Reply to: Tempenture gauge needle on the rise ??, rjb44, Wed, 20 Mar 2002 22:56:46 Members do not see ads below this line. - Help Keep This Site Online - Signup |
When the engine gets warm, the thermostat opens and ports hot coolant into the radiator, and 'cool' coolant from the radiator flows back into the engine. The radiator works by having outside air flow over the radiator to pull the heat out.
When you're sitting in traffic, there is no airflow over the radiator, so it heats up. When the radiator gets hot enough - about 89C, the thermoSWITCH on the radiator turns the fan on, which pulls cooling air over the radiator. When you're driving along, the normal airflow is usually enough.
The temperature gauge shows the temp of the Engine. The fan switch operates on the temperature of the radiator. Since there is some radiator between the inlet from the engine and the switch, the engine coolant will be hotter than the coolant at the switch.
So, what does all this mean? In traffic, it's normal for the temperature gauge to creep up over half, then come down when the fan kicks in. You'll see the needle creep up and down over a period of minutes if you're stuck in traffic. One good solution is to go to a cooler (82C) radiator fan switch.
If the temp gauge isn't going close to or into the red, you're probably fine. That's normal. If it hits the red, or looks like it might, then you should check into the cooling system. Thermostats should be replaced every 2 years or so, along with a coolant flush. I like running a 82C thermostat and thermoswitch.
Good luck!
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