Packard Forum Index » Post-War (1946-54)

Which thermostat temp should I use? Live in coastal SC. 160? 180? 195? Using 7lb cap.

Standard was 160 for 51 models and was good for most places year round. In extra cold climates the higher value was used to provide a bit higher coolant temperature before coolant started to circulate in order to get better heater operation. In days of alcohol antifreeze lower temp thermostats were common so the alcohol would not reach its boiling point. In hot and dry desert climates, when available a lower temp thermostat was used so it would open a bit earlier and not allow coolant temp to get too high before starting to circulate. In some areas of the country it was not uncommon to have the thermostat changed as part of spring and fall lube and checkup services.

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Thanks. I'll do the 160.

Piggybacking... is a 170 correct for a 55 engine in a cool climate (PA)?

I don't think it matters too much between 160, 170, 180. That's just the temp at which the thermostat opens. The cooling system as a whole should regulate the heat within a comfortable range regardless of what the thermostat temp is. I believe I have a 170 on my '54 Panama and the engine typically holds around 180 for normal driving and temps. Warmer temps will get it up to 190-195. My dad's '38 doesn't have a thermostat, just a shutter thermostat to control air flow across the radiator. The cooling system and fan keep it at about 170.

I run 190F in my vintage vehicles. If it won't run on 190F stat, you have other issues. 190F will ensure you're expelling moisture and plenty of heat for the heater.


Earl

I'd agree. In Winter, 180 to 190 F are a good idea. Cleaner engine, better mileage, better heater operation, longer oil life.

A cooling system in good condition will run about the same temperature in hot or cold weather with a good thermostat.
My car has an early style 154 F thermostat, but it runs 180 to 190 in summer, and about 175 in cool weather.I believe the radiator is restricted to some degree. I reverse-flushed it and it reduced the average operating temperature as indicated by the gauge somewhat. The car never boils over. Indications are the radiator has little or no reserve cooling capacity, since higher speeds or long hill climbing cause the temp gauge to rise.

(1937 120, non-pressurized system. "Green" anti-freeze 50/50.)

A non-pressurized system needs to run 180 or less in hot weather, especially at higher altitudes.

50/50 basic green coolant boiling point is 223F.

On pressurized systems, you gain 3F per psi of pressure above boiling point. So a 4 psi cap would push you 12F above boiling point in addition to the 223F coolant. So combined you'd have a boiling point of 235F.


Earl

Good discussion. Another thing to keep in mind is the rating on the thermostat (e.g., 170F) is when the stat starts to open. It takes about another 10 degrees for it to be fully open. So, a 170F rated stat will be fully open around 180F. Altitude also makes a difference. Here in Santa Fe (7,200 ft. above sea level) unpressurized water will start boiling around 195F.