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Re: High temp readings Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Tue, 1 May 2001 13:36:58
In Reply to: High temp readings, JMC, Tue, 1 May 2001 13:20:44 Members do not see ads below this line. - Help Keep This Site Online - Signup |
There are two systems going on here. The thermostat decides when to allow coolant from the engine into the radiator, and the temperature gauge reads engine temperature. The fan(s) come on when the radiator gets above a certain temperature. So the fan thermoswitch (on the radiator) knows nothing about what the temperature gauge says.
Under normal conditions, you start a cold car, and the thermostat is closed. It stays closed, and the coolant circulates in the engine, heating up (temp gauge rises). At some point the thermostat opens up, and some of that hot coolant makes it to the radiator, replaced by cooler coolant from the radiator - the engine temperature drops, the thermostat closes, and the temp gauge drops a little. The engine warms this coolant up, the thermostat opens, and the cycle continues. After a while the radiator is about the temperature of the engine, and the thermostat stays partially open.
This 'bobbing up and down' of the temp gauge is more obvious in winter, because the coolant is really cold on a 20 degree day compared to a 200 degree engine. In summer, the coolant has been sitting out on a hot parking lot, and may already be 100 degree (F). So the difference isn't as great, but the actions are still the same.
If you're driving along, you get plenty of airflow on the radiator, and that pulls the heat out. If you stop in traffic, there is no airflow, and the radiator can't dump heat - it gets hot, and then the fan thermoswitch kicks on, and the fans create an artificial wind. The fans shouldn't be running if you're driving down the road - the fans can't produce as much airflow as even a 20-30 mph drive does.
First question - what temperature thermostat was put in? 92C? 87C? 82C? If a hotter thermostat was put in, you'll get great heat in the winter, but run hotter in summer. I find an 82C thermostat works just fine in winter unless you live where it regularly stays well below 0 degrees F.
If you put in a 82C thermostat, the car may run nicely on the highway, but still get very hot in traffic. Then you want to replace the thermoswitch with a cooler (say 82C?) version. The fans will come on sooner in traffic. You can overheat a car in freezing temperatures if there is no airflow over the radiator. Make sure your radiator thermoswitch is working properly - heck, just replace the thing with a cooler one, just to be sure.
, Tue, 1 May 2001 13:36:58 <-- Viewing This Message
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