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

Hello i have a 1951 Packard motor that when runs for a short time,the coolant slowly comes up over the rad.fill opening if i put the cap on it will over heat and boil out,when i turn the motor off the coolant poors out the top i find no water in the oil pan so i don't think it is a leak in the eng block
what would cause this to happen .Thanks in advance Frank

A couple of possibilities are the engine passages or water distribution tube is full of sediment and hindering circulation to point water is actually boiling in places & turning to steam pushing water out or the head gasket is blown and combustion gasses are doing the same. Since the water pours out when engine stopped, my guess would be the steam. A slim possibility might be the water pump or thermostat is shot and not circulating enough. Does there appear to be good flow in radiator when thermostat opens or engine warm but not to point of boiling?

Why run a compression test? Sounds like a blown head gasket is a good candidate.

EDIT - Meant to say "Why NOT run a compression test?"

In the packard literature there is a detailed procedure to back flush the engine from the head outlet flange with the lower radiator hose disconnected. try that back flow prodecure with a combination garden hose and air compressor to get the pressure up to unclog any passageways. I have found deposits comong out of the water distribution tube. Phred

I had pretty much the same problem with my 51. It turned out to be the wrong radiator cap. The right one has about a 1" drop (Distance from the top surface of the filler neck to the bottom surface where the rubber gasket is supposed to seal. Check that. The cap you have may be only about 3/4" which does not seal at all.

On the old cars with no overflow tank you need to leave 2 or 3 inches of space at the top of the rad to allow for expansion, if you don't do this the rad will overflow when it is hot.

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Yes, That is right however after the initial loss of water it would stop. All else being right the engine wouldn't overheat and boil over. I got my car from a guy that said the cooling system on 51 Packards were not as good as other years. Said he was always putting water in it and that it overheated on very short trips. I found out what was wrong when I saw water pouring out the overflow when the engine was still cold. Seems that they had replaced the radiator cap at some point with the wrong cap. It looked right from the outside and was a 7 pound cap and all but did not seal aginst the seat in the bottom of the filler neck. I put the right cap on it and have hardly had to put a drop of water in it in years.

BTW, He spent lots of money re-coring the radiator, replacing the water pump and thermostat. Good for me bad for him. All it needed was the right cap.