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Engine coolant temperature concerns seems to be a recurring theme, and we've had lots of discussions on senders, gages, fans, fan shrouds, radiators, antifreeze, and additives, but the one thing that no one has ever mentioned is how thermostats work.
If you have a 180 degree thermostat that doesn't necessarily mean the temp will always run at 180. What it means is that the thermostat BEGINS to open at 180 degrees. I don't have a set of specs for a 180, but a typical OEM GM 195 thermostat is speced to begin opening a 192 to 198 and is not full open until about 225 to 230, so maximum coolant flow does not occur until the outlet temp hits this range. The 180 would have similar specs only about 15 degrees cooler on all specs.
When our cars were new they would usually stay pretty close to 180, but as time goes by scales form in cooling system components which tends to raise temperatures. It's always a worry when you see the needle creep up in hot weather, particularly low speed traffic, but maybe we're over reacting.
GM says that engine friction, particularly ring and skirt drag, is less with higher coolant temperature, so best power is usually obtained with high coolant temps. A 50/50 mixture of glycol and water boils at 265 degrees with a 15 pound cap, so if you have a 180 thermostat and the temp. goes up to 220 or 230 occasionally, especially at idle in hot weather, it's probably no big deal. In fact, it's common on modern cars. If the fan, shroud, coolant pump, radiator, cap and other cooling system components check out, I don't think we should worry that much. Beyond this, if you have any emission controls, such as TCS or the vacuum advance running on an off idle port, rework it so you have full vacuum advance at idle. This will always reduce idle and low speed coolant temperature.
Okay, now I'll go put on my nomex before I check back for responses.
Duke
If you have a 180 degree thermostat that doesn't necessarily mean the temp will always run at 180. What it means is that the thermostat BEGINS to open at 180 degrees. I don't have a set of specs for a 180, but a typical OEM GM 195 thermostat is speced to begin opening a 192 to 198 and is not full open until about 225 to 230, so maximum coolant flow does not occur until the outlet temp hits this range. The 180 would have similar specs only about 15 degrees cooler on all specs.
When our cars were new they would usually stay pretty close to 180, but as time goes by scales form in cooling system components which tends to raise temperatures. It's always a worry when you see the needle creep up in hot weather, particularly low speed traffic, but maybe we're over reacting.
GM says that engine friction, particularly ring and skirt drag, is less with higher coolant temperature, so best power is usually obtained with high coolant temps. A 50/50 mixture of glycol and water boils at 265 degrees with a 15 pound cap, so if you have a 180 thermostat and the temp. goes up to 220 or 230 occasionally, especially at idle in hot weather, it's probably no big deal. In fact, it's common on modern cars. If the fan, shroud, coolant pump, radiator, cap and other cooling system components check out, I don't think we should worry that much. Beyond this, if you have any emission controls, such as TCS or the vacuum advance running on an off idle port, rework it so you have full vacuum advance at idle. This will always reduce idle and low speed coolant temperature.
Okay, now I'll go put on my nomex before I check back for responses.
Duke
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