160 vs 180 thermostats

I live in hot country and wonder which is best for my stock 1954 Cadillac, a 160 degree or a 180 degree thermostat. I'm only concerned with part-time summer driving.

Main reason for the 160F thermostat is to keep the alcohol based anti-freeze from evaporating out of the coolant too quickly. Both the 160F and 180F should be fully open by the time the coolant gets to, say, 190 so the engine should not boil over any more with a 180F than it does with a 160 and you'll get less sludge in the oil. I'm guessing that by '54 Cadillac had a bit of pressure in the cooling system so the boiling point of the coolant should be even higher than a non-pressurized system.

The thermostat's only job is to set the MINIMUM temperature at which the coolant will flow, not the maximum. I personally think the 180 is a better idea since your cooling system probably doesn't have the capacity to keep things below 160 anyway. I'm also of the opinion that a little more heat in the engine is good, although we all like to see a nice, cool gauge. If it runs without boiling over, a 180 is probably a better choice. What's in it now, what kind of temperatures are you seeing, and does it have trouble keeping cool now? The general health of the cooling system is critical, and if it's not up to snuff, a new thermostat probably won't cure it. But if it's working properly, it will be able to keep a rock-steady 180 degrees under almost any conditions, even in the hot desert.

Does this help?

Yes, the factory specs on the radiator cap pressure is 12 to 15 lbs. Also, to Cadillac in that day (as reflected in the manual) 160 degree thermostat was standard and 180 degree was considered high temp. I assume from this that they intended for owners of new or reasonably new cars to run 160 in the summer and warmer months and 180 in the winter. Fifty or more years later, I believe that when 160 degree is recommended, it is done so with the idea that most all driving is done in warm weather and if the radiator kicks in 20 degrees sooner, it provides a little bit of a jump on the car heating up. My car does OK in regards to overheating but after pulling a few grades in 90+ temps, I have to mind my Ps and Qs.

The thermostat's only job is to set the MINIMUM temperature at which the coolant will flow, not the maximum. I personally think the 180 is a better idea since your cooling system probably doesn't have the capacity to keep things below 160 anyway. I'm also of the opinion that a little more heat in the engine is good, although we all like to see a nice, cool gauge. If it runs without boiling over, a 180 is probably a better choice. What's in it now, what kind of temperatures are you seeing, and does it have trouble keeping cool now? The general health of the cooling system is critical, and if it's not up to snuff, a new thermostat probably won't cure it. But if it's working properly, it will be able to keep a rock-steady 180 degrees under almost any conditions, even in the hot desert.

Does this help?

Thanks Matt. I live at sea level (even though not on the coast) and most of the summer driving requires some pretty long grades with 90+ temps. It was such that I had to do that driving in the cool of the morning or I was going to get too hot. My motor is in good condition and my cooling system clean. To lessen my chances of overheating, I recently recored my radiator to have more capacity and better fin cooling than the stock radiator. I am running distilled water with Water Wetter. I did install a new 180 degree thermostat but I have a few Robertshaw 160 degree summerstats that look to be much better made the poppet type 180 I installed. So, the reason for my question is to determine if changing to the 160 degree would be a step forward or a step backwards in preventing engine overheat.

I'd stick with the recommended thermostat. I tried running a 160 in one of my cars that called for a 180 and it worked great in the hot weather. However, the car struggled to warm up in cooler weather, so much so, I had to put cardboard in front of the radiator to get it up to normal operating temperature.

Yes, the factory specs on the radiator cap pressure is 12 to 15 lbs.

I am running distilled water with Water Wetter.

If the references I've found are correct, a 15 psi cooling system with 50% ethylene glycol will boil at 265°F. An 85°F difference between thermostat opening temperature and boiling point should be more than enough if your cooling system is in half decent shape.

I'd stick with the recommended thermostat. I tried running a 160 in one of my cars that called for a 180 and it worked great in the hot weather. However, the car struggled to warm up in cooler weather, so much so, I had to put cardboard in front of the radiator to get it up to normal operating temperature.

This is accurate. 180 year around. Will keep the engine in normal operating range no matter the season.

I prefer to use the lower temp thermostat and a low pressure cap out of respect for the old radiator and cooling system. I don't want to blow a rad or rad hose. Never had a problem but then, I don't live in California.

I prefer to use the lower temp thermostat and a low pressure cap out of respect for the old radiator and cooling system. I don't want to blow a rad or rad hose. Never had a problem but then, I don't live in California.

Depends where in California you are.

Where I am now you'd have to have a cooling system in really, really shape to have a problem with casual old car driving. But I do sometime drive into "the Valley" where temperatures can be high. And I learned my cooling systems where I was raised in southern Arizona where, in addition to high temperatures, you had to deal with very hard water.

I'm guessing that the original poster is in the Valley somewhere between Modesto and Red Bluff. Only area that I can think of that is near sea level but hot in Northern California. It can get hot up in the Willits area but I think that is a bit above sea level.

Depends where in California you are.

Where I am now you'd have to have a cooling system in really, really shape to have a problem with casual old car driving. But I do sometime drive into "the Valley" where temperatures can be high. And I learned my cooling systems where I was raised in southern Arizona where, in addition to high temperatures, you had to deal with very hard water.

I'm guessing that the original poster is in the Valley somewhere between Modesto and Red Bluff. Only area that I can think of that is near sea level but hot in Northern California. It can get hot up in the Willits area but I think that is a bit above sea level.

From Sacramento and it was 106 today.