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

I question whether coolant going too fast through the radiator would be an issue. For one thing, it would go fastest at high speeds in hot weather.
For another, given that the coolant is recirculated, the faster it passed through the radiator, the more trips it would make in any given time.
That would tend to keep the entire radiator core fairly hot, which would increase its heat-to-air rejection efficiency.

Back in the day cooling systems were serviced twice a year: In the fall to add antifreeze and a thermostat; and in the spring to flush the system, add water with a water pump lubricant and remove the thermostat. When the thermostat was removed it was "gutted" and the base reinstalled so as to keep the flow rate restricted. Rinse and repeat.

The attached PDF contains a graphic depiction of the data I’ve logged on my ’48 Deluxe.

The red colored curves are with the cooling system configured with a modified 1 inch 160F thermostat. The range of outside air temperatures for this data set is 68 – 92F, but whenever this thermostat is installed, which currently is all of the time, I constantly compare the coolant temperature to the prevailing ambient temperature as reported by the Weather Channel. This cooling system so repeatable I first make an estimate of the ambient temperature, and then look it up on my phone and will rarely be more than a few degrees off.

The darker lines represent the relationship for the same car without a thermostat installed. The range of outside air temperatures for this data set is 54-105F. I’ve concluded that this configuration should not be used in the cool weather because of the inability for the engine to achieve a reasonable coolant temperature.

My conclusion is/was this cooling system runs cooler without a thermostat installed, but this configuration should be avoided whenever the outside air temperature is at, or below, approximately 70-80F, but otherwise if I wanted to lower the coolant temperature by roughly 10F, all I would have to do is remove the thermostat and make another gasket from a Cheerio’s box.

dp

Attach file:

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48 Packard No Thermostat 001.pdf Size: 269.12 KB; Hits: 26

My understanding of the role of thermostats in regulating engine temperature is thus. The thermostat helps to regulate flow through the radiator so that the coolant can fully cool by the time it reaches the bottom before it is circulated back into the engine. Otherwise the coolant going back into the engine is now hotter, which increases the temp overall, making it harder for the cooling system to keep up.

At this is what I've understood from all that I've read. Maybe this has more to do with modern cars.

My dad's '38 Super was apparently designed without a thermostat in the engine block, relying on the grille shutters to regulate the temperature. During my testing the engine has never gotten over 175 degrees....but I'm also running a variable electric fan.

I run a modern thermostat in my Panama. I can't remember what it is, but I think it was a 160? Car has done well and regulated the temp pretty well. Never overheated. Radiator is rebuilt, but have not flushed the block, or pulled the distribution tube.

-Kevin

The radiator's ability to get rid of heat is related to how much hotter it is than the air that is passing through it, and how much air is passing through it.

The speed at which coolant moves through the radiator in a recirculating system affects how much heat it can dissipate under a given set of conditions.

A sluggish flow of coolant will result in a radiator core that is much cooler near the outlet than it is at the inlet. This will reduce cooling effectiveness of the radiator. The radiator has to be able to dissipate heat at or above whatever rate the engine is adding heat to the coolant. A hotter radiator will dissipate more heat than a cooler one. A fairly brisk coolant flow through both the radiator and the water jackets is desirable. Both the radiator and the water pump have capacity in excess of the engine's needs under ALL operating conditions, assuming they are in good condition. Less time in the radiator means more trips through the radiator at a higher temperature, thus more heat dissipation, unless flow is reduced by the thermostat.

Thermostatic shutters regulate the cooling system's ability to dissipate heat by regulating the flow of air through the radiator. The system works well, combining high coolant flow rates with temperature regulation via controlling air flow. Drawbacks are expense and complexity.

All - thank you so much for all the information and perspective on this. Absolutely fascinating. Certainly have a new appreciation for that little space station-shaped object in the head!

I'm curious if anyone has used thermostats that are marketed as "high-flow," and they advertise a larger opening for increased flow, something like this:

autozone.com/cooling-heating-and-climate ... gold-thermostat-15356dlg/380816_0_0

Actual advantages, or marketing spin?

I'd think it might have some advantage, maybe, but without knowing what the flow rating for the original spec thermostat is, you'd be guessing. I replaced an original looking bellows type with a modern stat that looks just like the one in the pics. The car ran much hotter, BUT, the original style is a 153 F and the replacement is a 180 F, so that really doesn't mean much. I put the original looking one back in and the car runs cooler once more, but it still runs hotter than I'd like in hot weather. Most likely, my radiator is partially clogged. I think that you'd be fine with any thermostat that fit correctly as long as the cooling system is in good shape and the temperature rating of the thermostat was appropriate for the application. Problems almost always relate to a problem or problems in the system, rather than any brand-to-brand difference in thermostats that carry the same temp rating.

Depending on year Packard offered thermostats with varied ranges depending on where or when they were to be used. Prewars were not as well documented as postwars but there is mention in some of the service articles.

Postwar thru 54, most of the thermostats are listed in the parts books. Standard was around 160 for most use. If a customer lived in a very cold climate they offered a higher degree of around 180 for winter use so the engine would run at an increased temperature for better heater operation. When using alcohol antifreeze they offered one around the 145-150 range even though the heater would not work as well. They even suggested using a non pressure cap along with the lower temp thermostat if alcohol antifreeze was in the car. Without increased pressure antifreeze would not be able to get as hot and the alcohol would not be as likely to boil off.