1940 Century radiator temperature differential

The Century stays pretty cool at highway speeds, but quickly heats up at idle or parade speeds. The radiator is an aluminum aftermarket model (supposedly high capacity), but my inlet and outlet differential stays at about only 10 degrees all the way up to about 205 inlet (as high as I let it go before turning on the added electric pusher fan). Seems to me the differential should be greater than this. Anyone know what it should be?

I wouldn't be concerned about differential temperatures as long as it does not boil over. What matters is that the maximum temperature stays below 210 degrees to avoid boil over. My old cars run between 180 - 200 degrees and that varies only slightly with outside temperature. Older cars actually run better when they are running just below boiling... With multiple fans, your issue may be getting air out of the engine compartment. If you still have the engine pans installed, you might consider removing them or block your hood open slightly to increase air flow.

G'day Rod,

Not knowing much about your car, I'll ask the old "Have you checked that the thermostat bypass valve is fitted ??" question.

Your problem may be due to low circulation.

Just a thought.

Danny

Thanks, Mark, for the calming words. I'll check the pans. Danny - good advice. I've only had the car about 18 months and the seller (a good friend) told me the valve was there, but maybe today's a good day to check for myself. One big reason I would like to see it run cooler is I can hear the gas boiling in the carb when I stop after it has gotten a bit hot and I figure that has a lot to do with the fact it needs a few seconds of cranking to get her going again and is quite easy to flood. I just got back a couple of days ago from a 7-day tour which included 3 almost 300 mile days and she never failed to start --- eventually.

I had a similar problem with my '30. Part of the cause was that the water pump was not doing much pumping. After a rebuild, the engine cooled much better. The other issue I had was a fan pulley that was to large which made the fan spin at much slower then it should.

I had a similar problem with my '30. Part of the cause was that the water pump was not doing much pumping. After a rebuild, the engine cooled much better. The other issue I had was a fan pulley that was to large which made the fan spin at much slower then it should.

Thanks. Good things to check. You know a good method for checking the flow rate so I don't have to pull the pump for a visual?

Rod, are you running a pressure cap? I am not sure, but seem to remember the '40 was a pressure system. My '50 is pressured to 7 lbs. At this pressure, boiling is some where north of 220. The engine will be fine at these temps, assuming good circulation.

Ben

Rod, are you running a pressure cap? I am not sure, but seem to remember the '40 was a pressure system. My '50 is pressured to 7 lbs. At this pressure, boiling is some where north of 220. The engine will be fine at these temps, assuming good circulation.

Ben

Yes, Ben, same as yours. I figure somewhere around 235 to boil.

Sorry, but I'm not familiar with the setup on a '40. On my '30, the pump is easy to take of the car. Once we got it off, we hooked it up to an electric drill to spin it with water fed from a bucket. The issue turned out to be a large gap between the impeller and the housing. A new impeller from Bob's made a huge difference. I also run the car with distilled water and "Water Wetter" during the hot months. That combination is good for a 10-15 degree temperature reduction.

Thanks. Good things to check. You know a good method for checking the flow rate so I don't have to pull the pump for a visual?

I use a laser pointer type infrared temperature gun and on my 53 Special with Dynaflow and power steering I find a temperature drop between the top tank and the bottom tank of about 20 degrees F at idle, fully warmed up. Moving at highway speed, the drop must be greater as the needle on the gauge drops to below the N for "normal".

Joe, BCA 33493

I use a laser pointer type infrared temperature gun and on my 53 Special with Dynaflow and power steering I find a temperature drop between the top tank and the bottom tank of about 20 degrees F at idle, fully warmed up. Moving at highway speed, the drop must be greater as the needle on the gauge drops to below the N for "normal".

Joe, BCA 33493

Yeah, that's what I'd like to have, at a minimum. Still looking for the solution. Staves off boredom, I suppose.