: radiator cooling in cold temps



stoveguyy
11-28-12, 07:27 PM
system is pressurized which raises boiling point of coolant. will car overheat if cap is loose and the outside temp is 20F? i know motor is hot and radiator might have reduced cooling needs when its cold. a/c is not working either. i was wondering if it matters if system had less than 15-17psi?

Submariner409
11-28-12, 07:37 PM
System pressure is used for several reasons, one being to raise the boil point up to about 265. Another is to assure that the water pump does not cavitate: it's a centrifugal pump and needs "solid" coolant fed to it in order to properly move the tremendous volume of coolant through the engine needed for proper heat transfer. Run a cooling system at atmospheric pressure and you most definitely run the risk of overheating at moderate to fast highway engine speeds.

Remember - cap pressure or not, your thermostat is set to assure most efficient, safe engine operating temperatures - and for us that is from 188 to 206 - unpressurized coolant boils at about 218 to 220, so you're on the edge with no system pressure.

Running your system with no pressure does not, in any way, stall off or prevent any sort of perceived engine "damage" - matter of fact, it nearly guarantees some damage.

stoveguyy
11-28-12, 09:56 PM
Odd questions usually have a backstory. My radiator is cracked and leaks. I was wondering if no system pressure would lessen my coolant leak? Yes I intend to replace radiator.

Ranger
11-28-12, 10:03 PM
i was wondering if it matters if system had less than 15-17psi?
Not much. Using this chart and interpolating between 12 and 20 psi (with a 50/50 mix) it comes out to about 2 degrees per pound of pressure.

stoveguyy
11-30-12, 03:53 PM
Do u think the system might boil over due to hotspots if rad cap is loose? I would think coolant would boil around head area at atmosphere pressure.

Ranger
11-30-12, 04:15 PM
Certainly is possible (probable). A lot of factors will have an affect on it, like ambient temperature, engine load, air flow through the radiator. I would not recommend trying it though. Why the concern or is this just a generic theory question?

stoveguyy
12-03-12, 11:54 AM
I ordered new radiator online. Not here yet. Just trying to minimize coolant loss till it arrives. It's 20f today. U can make a false assumption cooling needs are minimal when it's cold but motor is still 200f and needs to be cooled properly.

Submariner409
12-03-12, 05:30 PM
I ordered new radiator online. Not here yet. Just trying to minimize coolant loss till it arrives. It's 20f today. U can make a false assumption cooling needs are minimal when it's cold but motor is still 200f and needs to be cooled properly.

Remember: The heater coolant circuit in these cars is full flow at all times, very efficient, and that circuit heats to operating temp LONG before the thermostat hits 188 and starts to open. I'll bet that at 20 F and the heater fan on 2 or 3 the thermostat barely opens at all in easy driving.