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I'm trying to find some information about pressurized cooling systems.

1. What year did Packard go to a pressurized system?

2. Can I pressurize my system? I have a re-cored radiator and a new reproduction water pump, the main thing I'm worried about is the seal of the water pump. The main reason why I want to pressurize my system is for when the car is sitting in traffic.

3. Would I benefit from pressurizing my system based on the above information?

Also I'm in the process of fully rebuilding my engine, I had the block and head acid dipped so rust/corrosion causing an issue in the cooling system is not a factor

All responses appreciated, thank you very much.

1. Not sure, but 1941 was pressurized, 4 lb for non AC cars.
2. Perhaps, but to what gain? The car was engineered with plenty of cooling capacity with its original system so if you have the system in good condition, you shouldn't have a problem sitting in traffic. Many of us with older Packards crawl along in July 4th parades on 95 F. days and do just fine without a pressure system or overflow tank.
3. No benefit apparent to me.

So, now a separate question, is it common for non pressurized cars to boil over when sitting in traffic? I live in inland southern California, we got temperatures as high as 118 this summer. That, in traffic, is what I'm worried about. That also is not a daily condition here but still

... is it common for non pressurized cars to boil over when sitting in traffic?


Common? With a cooling system in good condition, no it is not common, more like highly uncommon. When these cars were new they were engineered to perform satisfactorily in prevailing typical conditions in the markets in which they participated. With that said, I wouldn't call prolonged idling in traffic in 118 degree heat the kind of typical condition engineers took into consideration when they engineered the cooling system. In conditions like that, I suspect even when new these cars would have had problems coping. Pressurizing the system will raise the boiling point of the coolant but won't have much of an effect on dissipating the heat, I'd be more inclined to add a supplementary electric fan on the radiator front.

The large upper radiator tank cannot handle any pressure, which I learned the hard way but fortunately I saw it in time to prevent any serious damage. Using a 12lb cap, I could see the tank physically expanding as it built up pressure. You MAY be able to get away with a 4lb cap but nothing higher and you'll likely have the change the tank's neck to do so as modern caps are quite different in how they attach.

I am with Dave (Owen Dyneto) in staying with the cooling system AS IT WAS DESIGNED AND BUILT BY PARCKRD'S ENGINEERS at the factory.The radiators are not made to withstand pressure; this is not to say they do not cool efficiently and if the rad is re-cored, the water pump UP TO SPEC, and the block and head properly flushed, and all other impacting criteria being equal, there is no reason the engine should overheat. I say 'other impacting criteria' because there are a plethora of issues besides water circulation that can cause overheating like exhaust blockages, heat riser valve problems, engine/ valve timing issues, etc. I would think by the time a Packard engine 'boiled over in 118 degrees', there would be other things to worry about like gas boiling in the carb, vapour lock and fuel pumps getting too hot, et al. 118 degrees is pretty hot; not sure I'd want to be sitting in anything that wasn't highly sealed up and well air conditioned in that kind of weather, and that isn't most Packards I know of out there from the pre-war era.

Yes, I do not anticipate to drive the car in that heat(summer afternoon 118 degrees), however if it happens I just want to be prepared.

I asked two close friends of mine who are both in the automotive field. Both know a lot about pre war cars in particular and they both recommended to at least see how it runs first, and if overheating issues do present themselves(which they shouldn't) to then take the action needed(whatever may be necessary).

So anyways after reading suggestions on here, and taking friends advice I decided to leave the cooling system stock. I had the radiator re-cored before I tackled the engine build, but I did run the engine with the radiator. Taking all precautions necessary I dropped it off yesterday to have it flushed and flow tested, along with the heater core as it leaked. This will ensure that the cooling system is working at 100%. Every component of the cooling system has been gone through(radiator twice haha) and as I said the block was acid dipped so all of the corrosion was removed, therefore it should run as cool as if the car were brand new, if not cooler(upgraded radiator core).

12 lbs seems like a lot to me for a car of that vintage. I was going to do 4 lbs, perhaps a max of 7. The packing material in the water pump held up well with that much pressure?

Thank you to everyone for all the suggestions and I look forward to hopefully having this car on the road soon!

I doubt that the radiator"s tank can handle 7lbs and even 4lbs is pushing it! Best to leave it unpressurized as designed. Presuming also when the engine was acid dipped that the brass distribution tube was removed. If any overheating problems do show themselves, that's something to check.

Everything was stripped off the engine before I had it dipped. If I dipped the brass tube there may not be much of it left? I know the acid eats away at aluminum, not too sure about brass.

Everything has been cleaned and serviced to make it as close as possible to factory fresh.

I'm no too worried about the radiator being able to handle the pressure, but as I said the water pump was my main concern.


Doesnt really matter now anyways as I left it as is.

Some acids attack aluminum, others do not. Alkalis vigorously attack aluminum. Most common acids will attack brass. To give a better answer one would have to know which acid was used and at what conditions.