Radiator overflow tube leaks water after drive.

[Displayman]

Have a stock 47 Merccury flathead.
We go to cruises couple of times a week.
Temps been between 80 and 97 degrees out.
Every time we park the car after a 20 minute ride,
the overflow tube leaves about a cup or two of water/antifreeze
on the lot. Is this normal? Do I need to put an overflow container
on the car? I have check the antifreeze with a bulb tester and shows
it is good to 250 degrees.
Should I drain and flush the radiator?

Thanks for any input.

Bob-Hampshire, Illinois

[imnezrider]

Not uncommon with flatheads, especially if you are over filling the radiator. The coolant needs room to expand. You probably don't have a problem. Try this...next time(s), let it puke until it stops, same next time. When it finds it's "comfortable" level, it will stop doing it. Just don't let it get below the top of the core. Yes, you can put an overflow container, but it probably won't serve much of a purpose.

[Joe KCMO]

I agree, too much water to start. When watching the temperature range on my flatheads, they go from about 170 when running to almost 200 when turned off. With that is the expansion of water which has to happen with temperature increase. As long as you maintain the minimum water above the fins that is the way it is designed. I took the overflow tank off my car and vent to the ground. It spit up a couple times and now I dont even pay attention any more.

[paul2748]

You can install a coolant recovery tank. The hot rodders have nice stainless ones which install easily, look good and can be painted (flat black?)to make them look less noticeable.

I had the same problem with my 48 Ford with a 302. Always spit out water. I installed one of the tanks mentioned and it never did it again. And I know I didn't overfill it.

[G.M.]

Bob if the coolant temperature don't get much over 200 with a 4 Lb pressure cap you should lose NO WATER at all. If you do you have a pressure cap that is not working or a compression leak in the heads or block allowing compression pressure in the coolant which will open the pressure cap. A lot of pressure caps do not seat down on the seat about 1" down in the filler neck. You should feel about 1/8" of spring pressure as you push the cap down past the locking openings on the out side of the neck at the top. The rubber end on the cap must go down and hit that seat at the bottom of the neck before the under side of the top of the cap hits it's seat on top of the neck. For some reason over 75% of the caps I have seen don't hit the bottom seat and require a thin round gasket about 1/8" thick that sits down on that bottom seat. The water should be filled right up into the neck. it is a 22 quart system not 18 quarts. More water equals better cooling and no air in the system. Water with no air cools better than water with air mixed in it. The hoses will take the small amount of expansion below 200 degrees. I drove my 39 from FL. to Pa. 4 weeks ago in 2 days and it was between 100 and 110 both days and never lost a spoon full of water. It never go's down 1/2" in 6 months of hot weather driveing. My other old Fords are the same as well as my friends cars. G.M.

[296 V8]

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He didn’t mention having a pressurized system. I don’t think they are in 47, are they?
If unpresserized there is no presser cap and a recovery tank can sit there forever and never work….sep to catch what comes out…..non will get sucked back in.

[jimTN]

G.M. is correct. Also Preasured systems have been in Fords since 37 in one form or another. Another desirable addition would be to add one of Skip Haney's overflow tube pressure regulators. Have one on my 32 and one on a 29 Packard. They work great.

[G.M.]

I'm not sure what year they put the 4 lb caps on, maybe 42 ? A lot of radiators had the seat down in the neck but the over flow came off the top of the radiator tank so a pressure cap will not seal. On the 39 I mentioned above I pluged the tube at the top of the tank and brought the over flow out of the neck as it had the seat down in the neck. A lot of people have the idea pressurizing the cap is to raise the boiling point of the coolant so it don't boil over at say 212 degrees. This is NOT the purpose on the old Fords, it is to keep the water from backing out the over flow due to the back pressure caused by the restriction of flow through the radiator caused by the size, length and dirt in the 144 tubes. The pressure cap or Skips 3 lb valve ONLY holds the water from excapeing. Skips valve is only to be used on older radiators that a pressure cap won't work on. These engines should never get over 200 degrees, the pressure at 200 degrees is less then 2 lbs. As Jim found out keeping ALL of the coolant in the system keeps the engine much cooler. G.M.

[Displayman]

Many thanks for all the replies!
I will try driving several times without
refilling after these minor overflows
and see how car responds.
I am also going to check on the radiator cap.

Thanks,

Bob- Hampshire, Illinois

[gmc1941]

If you been on a long drive and pull in at the house and shut the engine off, you have alot of residual heat in that cast iron block with those ambient temperatures. GM is correct also...

[G.M.]

I mentioned above about making a gasket 1/8" thick down in the neck but I would start with one a 1/16" thick or less. If the gasket is to thick it will raise the pressure the cap opens. We don't want the pressure to get over 4 lbs before opening. If the end of the cap hits the bottom seat don't add any gasket. G.M.

[lotsagas4u]

G.M., checked my cap today, and it was not touching the bottom of neck. I bought one the O'reillys overflow tanks, it came with a section of clear tubing. I installed the tubing on my overflow nipple, attached other end to tank. I started the engine (cold), immediately coolant slowly started down the hose into overflow tank. I made a 1/8 red rubber gasket for the neck bottom, installed 4lb cap, started the engine and no more coolant flow. I drove the car 10 miles, temp was around 185 or so. I just removed the radiator cap, and you could hear pressure released when opened. I may need a thinner gasket. Car has a set of Shewmans 180 stats in also. This is a new Brassworks radiator, Thanks for the tip.

[G.M.]

Added pictures 5/27/17 for adding pressure cap on 39 Ford.
Also cut off and plugged overflow pipe at top of radiator. G.M.