I've got a perplexing issue in my 1951 F1. Now that things have warmed up here in northern Arizona, my radiator is spewing coolant out the filler neck. Water temp is running 190* whether driven hard or in traffic. If the fluid level is 2" below the top of the radiator, it won't spew out if driven easy. Driven 70+ MPH for a couple of minutes, and it pukes all over the fenders.
Replaced the radiator cap, flushed the system..... same results. I do have small aluminum overflow tank.
Friend says I have gas entering the system through a bad head gasket, warped head, or crack in the head/block. I can't see any bubbles with the motor running, but obviously can't look at the coolant at high speed when hot. Motor runs just fine.
Should I get a radiator shop to do a test? How conclusive is a test for HC? If gases are present, how does one pinpoint where to start?

 

I can't relate specifically to your setup, but my stock '69 Mercury has the original 429 engine and I don't believe it has ever been out of the car. It will puke coolant all over the place when I stop it after filling it to the top of the radiator tank. I keep it at about 3" below and it's fine. I've owned it for over 14 years and it's never been a problem. Some of the local old school mechanics around town concur that this is normal for some setups.

 

If you are running a recovery tank are you running the correct style radiator cap to work with it? If so then the cap is not sealing correctly to the radiator. Coolant should overflow into the tank and the tank should have its own overflow hose in case it gets overfull. Under pressure the coolant will go into the tank and then at shutdown the vacuum will pull the coolant back into the radiator.
If you are not overheating or blowing white smoke I would not suspect a blown head gasket.

 

If you are running a stock powered truck at 70 MPH with stock gearing, that is expecting quite a bit of it. So far as combustion gas getting into the system, many parts houses loan the test tool. All you have to buy is the test media.
Edit: I now see in the header, you're running a 460. So, what radiator are you running. I tried the original 226 CID six radiator with a SBC and could not keep the coolant in when running the 4 PSI cap. High speed, it would throw out the coolant. I went to a different radiator.

 

lots of pressure in the radiator usually means blown head gasket or cracked head.

If not lots of pressure... get a new radiator cap.

 

Thanks for the comments.
Looks like I'll get a shop to test for the presence of HC (hydrocarbons) and if the test is negative, look for a larger radiator. The current radiator is a 3 row unit that looks pretty good, but no idea it's internal condition. Perhaps the radiator can't handle the volume, although I would think the engine temp would climb in that case.

 

How sure are you that your gauge is working correctly?

 

Yes if the radiator is inadequate it would raise the temp.

I think the radiator is plenty for your engine, I have a 3 core with no shroud and I don't get that issue at all with my 460. The engine had a 190 t-stat in it when I bought the truck. Long story short.
It never puked with a 190 in it and temps showing 230~
No puke tank here though. I keep my fluid level 2" down in the tank as well
maybe a little more it's hard to judge by eye exactly.
Of course my issue was it getting too hot idling, never going down the road.

 

Gauge is accurate.
Just checked fluid level - looks to be around 2" below top of tank. I will take it out today and run it at freeway speeds to see what happens. Maybe I have the fluid level too high.
Doesn't get hot in traffic, nor at higher speed. I think the highest temp I recall is 200* but normally sits right at 190*.

 

While it appears the engine is running just a little warm (by 10 degrees), this can easily be because of the climate you are in. But, I agree- I doubt you have any system leak issue (including head gasket, etc.), but I would ensure you are using the correct radiator cap....one that should not have a lever "vent", etc.

With regards to the "spillage". One of the greatest impactors that has come to be are the "high-flow" replacement water pumps that were introduced (and still here) in the late 70's......although 99% of it is a better impellor design, it did increase the flow rate of coolant in the system.....Now originally, the increased flow was 3% IIRR which still gave a good amount of time for the coolant to absorb the heat and expel it at the radiator but over the years & especially in the mid 80's the engineers upped the design again and well, that's when we all starting to see our engines running warmer (you also have to remember at the time these same style water pumps were still in use on the new vehicles- which were designed for the increased flow).

On our Mustang the flow was so great that it would cause the radiator cap seal to "lift" under higher rpm causing fluid to expel, which we addressed with an overflow/recovery tank (had to home-build that one at the time), which today is a common standard so to speak.....you just may (very likely) have to increase the size of the overflow tank......1 qt + capacity for an overflow is really not that unusual.

 

If all else fails you could bring it over to my house and we might be able to come up with a solution, should be here most of the day. My Mustang has a 466 in it you might get some ideas on how to keep it cool.

 

Many thanks - in Bakersfield CA at the moment (birth of 3rd grandson!) but back on Monday. Will give you a call and see if we can meet during the week.

 

Follow-up on topic.
Driven 300 miles at all speeds in hot and cold weather - no spewing of coolant from the radiator. Apparently need to run the fluid level at least 2" below top of tank. Apparently this is how it's done on a big block ford.
Thanks for the replies and guidance.