VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 Radiator Performance (1940/216)

I have heard that there should be temperature differential from top of radiator to bottom of 20 to 25 degrees. I checked at the top hose and bottom hose with a infared temperature gauge, engine at idle and have about a 3 degree differential (engine temp at 180 degrees). I guess this differential would increase with increasded RPM which would improve water flow and air across the radiator. Anyone know what the ideal RPM would be to check this Temperature differential ?
The ambient temp was 80 degrees when I was checking this.

Thanks,

Wes Marquis

Wes,

I've had some troubles with the cooling system on my 40 1/2 ton pickup operating in high ambient conditions (above 90 F), so I installed two digital meat thermometers in the system so I could get some idea of what was going on while driving the truck. The thermometer probes are set into standard brass compression fittings (3/8" male pipe to 1/4" compression), one mounted in the heater return line port on the water pump and the other mounted in the heater supply port just beneath the thermostat. This, in effect, gives me a readout of the radiator inlet temperature (the heater supply port) and the radiator outlet (heater return port).

With a 90 degree ambient and the truck traveling at 50 mph on level ground, the differential is about 13 degrees. By removing the thermostat, the differential under similar conditions is about 10 degrees, which would indicate that the thermostat, though wide open, is still restricting flow slightly.

The last run I made was in 100 degree ambient at 50 mph, going up a 4 mile grade of probably 3-5%. The engine temp measured at the stock temperature sensor at the beginning of the grade was 185 and the differential across the radiator about 10 degrees. By time I topped the hill, the engine temp was 200+ and the radiator differential still around 10 degrees. The system did not boil, but would have had the grade persisted for another mile or so.

I don't know what the design differential temperature is across the radiator, but it sure would be nice to know in order to better evaluate radiator condition.

Mark Yeamans
VCCA #35724

wes, mark, i messed around 2-3 months on my radiator problems and found from a radiator shop that it was stopped up. boiling it out did help some but in the end i had to purchase a new radiator. gone were the heat problems i had similar to yours so now the temp stays in a more normal heating range. it may be a little expensive for a new radiator but it was worth it since you never know the condition of your old radiator internally. even if it is stopped up 10%-20% can be a real problem. maybe your local radiator shop can verify you of any stoppage or problems

Thanks Mark and Ken,

The information was a big help.........

Wes