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Newbie to Packard
I bought a 36 120B last fall. It has an R11 overdrive and it just runs down the road great. I am really happy with the car.
The guy I got it from said it had a new core in the radiator and the motor was overhaul 10k ago.
Here is the issue
going down the road the temp gauge say and stays at 180, if I let it idle for 20 min it goes up just a little. As long as it running the temp is good
When I shut it off, the temp climbs and it burps about a quart or more of coolant out the over flow.
Are these cars are prone to this problem? Is this something that happens to these cars because of a specific thing or should I just start with the standard flushing of the rad and the block and go from there
Thanks again for your attention
W

You've come to the right place for a definitive answer. Probably your thermostat (easy to replace) or the engine waterways are clogged up. But someone here can help you for sure.

One question would be the coolant level when cold. Typically most Packard radiators are filled to a level approximately 1 inch below the bottom of the neck to allow room for expansion. Those that are overfilled are prone to spewing out the excess.

Your temperatures sound normal for my 1938 120 (1602) with the optional warmer thermostat (used to improve fuel efficiency/mpg). However, some thermostats have no vent hole to reduce minor boil over or burping of gases, air or localized steam on stopping.
So a solution is to drill a ~1/8" dia hole in the thermostat flange. This I have done with success. Of course if I overfill the radiator it burps!

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Thanks guy, you are the best. Have ordered a new thermostat, will see that the vent hole is in it. Also will blow out the block and radiator while it is apart.
Thanks again, I will let you know how it works out
Will

wjames - The vent hole serves two purposes. First, it allows some small amount of coolant to circulate with the thermostat closed; and second, helps to prevent an air lock in the system when refilling it.

The 1937 115C and the 120C Packards are similar and have unpressurized cooling systems.

I have a 160F rated thermostat in my 1937 Six (115C). I would not recommend going to a higher temperature one. My Six's temp gauge registers about mid-gauge (180) regardless of ambient temp. It will move a little higher (195) if stuck in traffic, but quickly goes down once the car is moving again. It has never boiled over on me.

Also, since I do not have to worry about extreme low temps here in Austin I only run about a 25% mixture of antifreeze. This is enough to protect it down to about 0F and provide anti-rust protection. The less antifreeze used the more efficiently the cooling system will work. In New Jersey you probably need to use the max recommended mixture of 50-50 for freezing protection down to-34F.

(o[]o)

The problem is not the thermostat, if the thermostat were bad it would overheat while running. If it "boils over" when shut off then some part of the engine is above 212 degrees. This is usually caused by sediment/rust in the back of the block or a corroded water distribution tube.

Try removing the rear most core plug above the starter and see if there is rust/scale in there. Keep in mind the water jacket goes down an inch or so below the plug. If there is junk in there, remove all plugs, fish around with a coathanger and blast it with a pressure washer.

Let us know what you find