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

Several years ago Drew worked out a chart correlating the resistance of the 52 sender to the approximate temperature of the coolant. He also measured and noted how the resistance value would display on a typical 52 gauge. There is no way of knowing if the gauge was calibrated or even reading properly but at least it is a start. With the exception of a small number of 53 senders the same readings should be in the ballpark for all senders used from 51-56.

Here is Drew's information and by use of his resistance readings an additional note was made of what the approximate actual temperature would be if the gauge displayed numbers.

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All my Packards and Henney-Packards had heaters but if they did not come with it, the connections would have been plugged rather than looped around. Doing that makes quite a bit of coolant bypass the radiator.

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Very true and both the head and pump ports had a 3/8 NPT pipe plug in the opening if there was no heater. If there is a heater Ross has mentioned several times that if you bypass the heater -- even temporarily -- with a loop of hose it needs to be plugged to prevent a considerable amount of coolant from having a path around the radiator. He has suggested a wooden plug or a marble be inserted in the hose. Just make sure whatever is inserted cannot fit thru the nipple on the head or water pump so it can end up in the engine.

For a quick test, just squeeze the heater hose shut with a vice grip. And to eliminate confusion stick a kitchen thermometer in the filler neck of the radiator to see what you are really getting.

I don't find those engines prone to running warm except when a)clapped out with a lot of blowby b)timing chain way slack so the cam is retarded c) and this is the main one--initial ignition timing too late. That is usually caused by setting the timing with the idle too high with the vac and centrifugal advance already kicking in. I have had cars in with pointer bolted to the wrong pair of bolts on the timing cover too.

The heater hoses are getting pretty hot. I'll put a manual cutoff in one of the hoses to check if that changes anything. I currently have one of the radiator caps that has a thermometer built into it to watch the temp. It got to 220 the other day before I shut the car off. We've played with timing both ways to see if it made a difference. It didn't. I also pulled the exhaust pipe down from the manifold to make sure the exhaust "flapper" was open. It is definitely open and the exhaust doesn't have any restriction.

Thanks for the suggestions. I appreciate the help.

Both heater hoses being hot is a sign that coolant is short-circuiting through them.

Does the radiator get hot? It should get too hot to touch across the entire upper portion of the core, and a lot of heat should be evident in the fan's air blast coming through the radiator when the engine is warmed up. If the vehicle has a heater, does it blow hot air? If no heater, or the if the heater is inoperative, you do not want a hose connecting the heater hose inlet and outlet connections on the engine and water pump. There is a reason why the engine is running hot, if it actually is running hot. Is there any chance the lower radiator hose has a loose lining that is blocking flow, or that the lower radiator hose is collapsing due to pump suction? The engione is supposed to have a working thermostat. If it doesn't have one, get a 180F thermostat and install it, making sure that the thermostat is installed correctly. In some cases, a thermostat can be installed backwards, and in such a case, it may be very slow to open or it may not open at all.

Also make sure that the lower radiator hose has the reinforcement wire inside as without it, it could collapse partially or fully under the suction.

I appreciate all of the responses. I've checked everything mentioned. I pinched off one of the heater hoses, but after a while they both got very hot. There couldn't be any water circulating, but I assume the heat came from the engine just getting hot. I have one of the thermometer radiator caps on now and just let the engine run until it boiled over, which was about 225 on the radiator cap. The laser temp gun showed about 215 at the temp sender. Even then, the car shut off fine and then restarted like it wasn't hot at all. I loosened the distributor and moved the timing around. That didn't help. The fan is blowing very hot air. At this point, I'm just wasting my time. I don't even know if an engine rebuild would help. I'd hate to do that and then have the same problem. Even then, it runs great, doesn't smoke, and has good power.

Have you had the radiator inspected? Perhaps someone pinched off a few tubes to fix a leak? Could it be partially plugged?

What are the compression numbers across the cylinders?

I had a car with a head gasket leak that would leak exhaust gas under pressure into the coolant. This would cause the coolant to heat faster than it could be cooled, and then it would blow coolant past the cap.

Besides that, the motor always ran great. I just had to top off the coolant every day.

You could see bubbles in the radiator with the cap removed. But I know they also have a more specific test for that.