9-g radiator cap question blowing out coolant, no head gasket issues

[robertsamx]

Hellow all, I have a 50 9-g champ. On hot days 90+ it will blow out 1 gal out the overflow when i drive it on the freeway. Around town on city streets its fine. It runs at 3/4 most all the time, which is ok to me, but the freeway pukeing needs to stop!! I wonder about the radiator cap, on todays cars the caps are pressure caps rated at 13# to 19# depending on the car. and the cap seals the coolant into the tank so it must overcome the set pressure to blow out into the overflow tank. But on my radiator the cap dose not have a spring seating a gasket in to the bottom of the filler neck, its just a cap simular to a old school gas cap. so my question is this, do they make a radiator cap with a pressure spring that seats all the way down into the filler nick, or do i need to have a radiator shop swap out to a new style filler that will take a pressure cap?? Can the cooling system handle 13 to 15 pounds?? Thanks RC

[Tom Bredehoft]

Expect the system to take 7 pounds pressure, and expect the coolant to expand about a quart as it heats from air temp to 180 deg. if there isn't room for that expansion, it will puke.

Also, as it heats, and generates the 7 # pressure, the boiling point will rise to about 225 deg. So your engine can run at 220 deg without boiling over.

[wolfie]

Hellow all, I have a 50 9-g champ. On hot days 90+ it will blow out 1 gal out the overflow when i drive it on the freeway. Around town on city streets its fine. It runs at 3/4 most all the time, which is ok to me, but the freeway pukeing needs to stop!! I wonder about the radiator cap, on todays cars the caps are pressure caps rated at 13# to 19# depending on the car. and the cap seals the coolant into the tank so it must overcome the set pressure to blow out into the overflow tank. But on my radiator the cap dose not have a spring seating a gasket in to the bottom of the filler neck, its just a cap simular to a old school gas cap. so my question is this, do they make a radiator cap with a pressure spring that seats all the way down into the filler nick, or do i need to have a radiator shop swap out to a new style filler that will take a pressure cap?? Can the cooling system handle 13 to 15 pounds?? Thanks RC

It sounds like at some point your radiator cap was replaced with an old school gas cap. I believe it should have a pressure cap as TomB suggests. Steve

[mbstude]

A 50 Champion does not use a pressurized cooling system. The cap you have is likely correct.

If you're filling the radiator up full to the neck, you can expect some coolant to puke out.

[StudeRich]

It really does not sound like the radiator is cooling efficiently and needs a top to bottom temp. differential check, if not significantly cooler at the bottom, consider rodding it out or re-coring it.

Is the block really CLEAN? Fan belt tight enough? Ignition Timing set at 4 degrees? No more than 50% Anti-Freeze?

In Eastern Washington it's hot enough to run a 160 Thermostat in Summer and will certainly need a 180 in Winter.

Most early non-pressurized radiators can take a long reach (1 In. Reach) 4 Lb. or 7 lb. Cap, but no more, same as '52 to early 55's did. These are no longer found in Parts Stores, but available at Studebaker Vendors.

[41 Frank]

Many times when an engine heats up at highway speeds and looses coolant but stays relatively cool in town it indicates a circulation problem such as a plugged radiator.

[53k]

Advance Auto, Autozone, Car Quest, NAPA, Pep Boys and probably others sell radiator overflow kits that will solve the puking problem. The two I have installed recently on pressurized systems both had instructions and a gasket to add for non-pressurized systems. I like them because you can have a completely filled cooling system (no air space) which gives you better cooling. As the coolant expands, the overflow goes in to the overflow tank. When it cools it pulls the coolant back in to the radiator. However, if your car is running hot enough to boil out the coolant, it's probably not going to help.
I first installed one on my '64 Champ back in '69 when I was pulling heavy trailers. It was an expensive kit, but now the plastic ones sell for $5 and up. the first plastic one I installed was on my '64 Avanti. It ran cool, but every time I stopped, it would puke a little (probably had the radiator too full). On our Potomac Chapter Route 66 trip I finally decided to do something about it- went to Pep Boys in Albuquerque and got a kit for $3.99. Problem solved. All modern cars use overflow systems. You add coolant to the overflow tank, not the radiator.