1939 radiator overflow tank?

[38convsedan]

Have any 1939 owners added a radiator overflow tank?
My 38 CS has ‘39 horns mounted on driver side inner fender (out of necessity), not leaving much room. Would be curious to see how it’s been done…

As always, thank you in advance!
Steve

[JayChicago]

But why would you want an overflow tank? Your radiator already has a built-in expansion tank above the radiator fin-tubes. If you don't fill the expansion tank, leave room for expansion, you should not have any overflow to catch. May overflow a little the first drive after filling, but then it will find its own level and not overflow again unless the engine gets overheated.

[38convsedan]

My car expels over a gallon of coolant over several trips when filled at top of radiator veins. It then expels a small amount foamy coolant at almost every trip after that.
Is this normal?
I don’t want to have it eventually over heat with warmer weather approaching here in central Florida.
(Previous owner had radiator cleaned out by radiator shop, motor is rebuilt 8BA—less than 500 miles on it).

[pistonbroke]

Two things . First your engine is still tight and needs some miles on it to loosen up a bit more ,so is it running on the warm side?, two , do you have the correct cap on the radiator? I don't recall if 39 can use a pressurized type or not but it may help. A last thought would be to back flush the radiator. It may have been cleaned out when the engine was being rebuilt and when the engine was put in a lot of rust and iron deposits that got knocked loose during the rebuild prosses could now be in your top tank. Just a thought, Some rebuild shops are not always looking at the cooling passages as much as we would like. Are you running thermostats? They do slow the flow down some what, so if its a case of the flow rate being higher then the radiator can handle fluid would be forced out the over flow. This however takes us back to the radiator needing some attention as it should be able to handle that flow volume.

[19Fordy]

Your coolant shouldn't be "foamy"?
GOGGLE: "What causes radiator coolant to be foamy?" to get some ideas.

Even though engine is new it might be a leaking head gasket.
Check torque on heads.
Do a pressure test on the system.

[flatjack9]

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Are you using anti-freeze? If so this could be the problem. Years ago when I got my 39, I had the same problem. I put a glass tube in one of the top hoses and could see the coolant foaming. The faster I ran the engine, the more it would foam which would then spill out the overflow. Switched to water and have not had an overflow in 20+ plus years. Can't explain it, but it has worked for me.

[Kube]

There's an issue somewhere else just as others have suggested.
You already have an expansion tank at the top of your radiator.

[38convsedan]

No water in oil and no oil in coolant. What are the physical signs of leaking head gasket?
Should coolant be visible at top of cores?
I do notice some small bits of rust in radiator when filled to top of cores.
But after a few drives, coolant level drops due to overflowing.
Car doesn’t run hot.

[pistonbroke]

Yes I believe you should see coolant above the tubes in the top tank. Just because your car isn't running hot doesn't mean you don't have a flow issue. If the radiator just cant quite handle the volume the water pumps are sending it it has to go somewhere . The good news is your new engine is running good and your cooling system is working. I never heard, are you running thermostats? There is a simple answer here somewhere. Tim

[Kube]

Originally Posted by pistonbroke

Yes I believe you should see coolant above the tubes in the top tank. Just because your car isn't running hot doesn't mean you don't have a flow issue. If the radiator just cant quite handle the volume the water pumps are sending it it has to go somewhere . The good news is your new engine is running good and your cooling system is working. I never heard, are you running thermostats? There is a simple answer here somewhere. Tim

Tim, Like you, I hope the answer is a simple one.
Me?
I'd pressure test the system at 4#. If the system holds the 4#, then I'd
pull the thermostats out if they are currently installed. If they are not installed, I'd install them. Just to see what difference that might make.

[blucar]

Many people overlook the fact that the average radiator prior to '40-41 does not have a seat in the neck for a pressure cap to work, ergo, a pressure cap is useless.
All of my pre '40 vehicles have had the neck replaced with one that will accept a pressure cap, generally a 7 lb.
The stock expansion tank on vintage radiators is a completely different item than a coolant recovery tank.
If the coolant in a expansion tank gets hot it is expelled and lost out the overflow tube.
A coolant recover system allows the coolant to expand into the recovery tank, when the coolant cools down vacuum within the system pulls the coolant back into the radiator/engine, eliminating air within the system and coolant loss.
Basic chemistry 101, heat expands, cool contracts.

[pistonbroke]

Blucar , Thank you for clearing up the first years ford had pressurized cooling systems. As I stated earlier I was not sure. As for the recovery tank system I agree, that is how it works but its designed to work with zero air in the upper tank . When our Vintage ( before 1974 ) cars were designed there is supposed to be space for the coolant to expand and compress the air in that space to generate the needed pressure or in the case of our older still non pressure systems just expand and contract without going out the over flow tube . The OP could use a burp tank as he asked about and it would probably work but it addresses the symptom not the problem causing it as I see it. Thanks again ,Tim

[JayChicago]

Tim
Excellent response.

[38convsedan]

Barners—thank you for you thoughtful and informative input.
I will check with previous owner regarding thermostats.
Spoke with Skip Haney—after describing symptoms he suggested updating gasket at base of radiator cap and using one of his overflow hose check valves (ordered-check’s in the mail).

[Gene1949]

My reasoning for an overflow tank is quite simple
Take a water glass and pour the water from that glass into a another glass. In the receptacle glass you have air bubbles. You are doing the exact same thing when the upper tank has air in it. Air would become part of the coolant.
To me it stands to reason air in the cooling system has 2 detrimental effects.
(1) corrosion.
(2) air doesn't cool very well compared to a liquid.

[38convsedan]

Another consideration…Did 1950 8BA engines have pressurized cooling systems?
I’m running a 1950 8BA on a 1938 unpressurized cooling system… Are 8BA water pumps and coolant flow same as stock ‘38 flathead pumps/coolant flow?
Curious if this is a relevant variable…

[pistonbroke]

Yes the 8ba's were pressurized systems. I don't know for sure about the output volumes of the two different pump styles, but I would be surprised if it was significant. Good thought though. Tim

[chap52]

Anyone remember those glass jars clamped in the engine compartment that were used for an overflow tank? Flash backs... I hope this was a real thing... lol Chap

[38convsedan]

So I ran engine with rad cap off to observe. Ran engine at idle and at higher speed at times, temp came up to about 160-170 and held steady. When revving engine, noticed foaming when held at higher speed after warmed up, then foam would dissipate when rpm’s dropped. The foaming was not significant, ie it never became super viscous nor did it ever over flow filler neck. It would dissipate when returning to slower running speed. At no time did coolant overflow the cap area. To start, coolant was filled above cores, just above base of filler neck.
Again, no oil in coolant and no coolant in oil.
Hoping Skip’s check valve and new rad cap will solve issue of coolant overflowing.

[38convsedan]

Engine does not have thermostats according to PO.