Radiator overflow tank

[mach92bill]

Hi, I'm running a 261 6 behind a stock '54 GMC radiator on a 1954. After running, the coolant gets low, probably through the overflow tube. I figure if I run a piece of tubing from the overflow pipe to a tank should solve the problem. Am I on the right track?

Any help appreciated. Thanks

[xaircav]

Originally Posted by mach92bill

Hi, I'm running a 261 6 behind a stock '54 GMC radiator on a 1954. After running, the coolant gets low, probably through the overflow tube. I figure if I run a piece of tubing from the overflow pipe to a tank should solve the problem. Am I on the right track?

Any help appreciated. Thanks

A generic auto parts store tank works for me.

[mr48chev]

I bought a shiny one off Ebay a while back for 16 bucks for mine A guy could make one pretty easily out of steel tubing

I'm not sure if the stock cap will let the coolant draw back in when the engine and radiator cool off though. It should as it needs to vent to the inside so the cooling system doesn't get a vacuum created in it.

[bosco]

Originally Posted by mach92bill

Hi, I'm running a 261 6 behind a stock '54 GMC radiator on a 1954. After running, the coolant gets low, probably through the overflow tube. I figure if I run a piece of tubing from the overflow pipe to a tank should solve the problem. Am I on the right track?

Any help appreciated. Thanks

I was running into the same issue. Tank was only 22oz expansion before it would puke. Went with a larger 53oz, problem solved. Fluid level has not changed.

[xaircav]

Originally Posted by bosco

I was running into the same issue. Tank was only 22oz expansion before it would puke. Went with a larger 53oz, problem solved. Fluid level has not changed.

I tried one of the metal cylinder ones too. Not enough capacity. Got the one in the pic and it works fine. Coolant level can be checked visually. The other issue with the tank was the hose from the Champion radiator was 5/16" and the tank had a 1/4' fitting. My plastic tank works fine and keeps air out of the system. I'm using the cap that came with the Champion.

[mach92bill]

Did you have to change the radiator cap?

[roger55]

Overflow tanks for down-flow type radiators are completely unnecessary and a waste of money and space. If your radiator is spilling over when at running temperature, it is being over-filled.
Down-flow radiators are designed to be run with the coolant level about an inch from the top to allow room for expansion.

Tanks are necessary with cross-flow type radiators. They are correctly referred to as coolant recovery tanks.

[Killer Bee]

Roger's right about that air gap.. fill 'em up close and run them up to temp with a pan under overflow hose..

they'll let go of the excess coolant on the first hot run and that'll be about the end of it..

track cars have to by most rules but even the most environmentally conscientious folks can manage to keep the asphalt clean without it..

[mr48chev]

I got caught up in the moment there but as Roger55 and Killer Bee said, you have to leave room for expansion in the tank on the radiator. That may mean that as long as the top of the core is covered when it is cold you are good to go. Once it has puked I'd check to see that I had coolant above the core and go again and check again when it was cold again until I figured out the level that it wants to run at. Yes when thinking about it I have been there, done that more than once.

[dsraven]

down flow rads are made with a large upper tank that also acts as a reservoir for extra coolant. they don't use a recovery tank unless on a newer vehicle that is required to recover any spillage. those systems also use a different rad cap with 2 rubber seals, one just under the cap that seals against the uppermost part of the rad filler neck in order to complete a seal with the recovery tank and one on the bottom end of the rad cap that seals the pressure in up until the point where the preset pressure is reached. theory says the system comes up to pressure and pukes out the excess into a recovery tank, then, when the system cools off and is looking to get some of that fluid back through a lower pressure inside the rad (from contraction of the previously heated coolant) it can draw back from the recovery tank. with a normal single seal cap, like these trucks came with, that would be hard to do because there would be air leaks where the larger rubber seal is missing from the cap. if you run a recovery tank then you have to replace the rad cap with a dual seal style cap.
first, check the rad cap to make sure it is good and blowing off at the correct pressure. this will require a pressure tester with a rad cap adapter. check the rubber on the under side, looking for hard rubber, a divet ring where it has sealed against the raised ring section of the filler neck, cracks or damage in general. next check down inside the neck to make sure it isn't damaged or distorted, this goes for the lock tabs on the neck as well. while looking in the rad check for blossoming on the ends of the core tubes as well and for the general condition of the rad and coolant.
next, on a cold engine, top it up with room temp coolant. then use a pressure tester to check the whole system for leaks. run the tester up to whatever pressure the system is rated for (it usually says a pressure on the rad cap but ensure it is the proper rated pressure for the sytem design). let it sit for 15-20 minutes and ensure it holds pressure. it is a good time to check the hoses , water pump seal, rad core and tank seams as well as the heater core and frost plugs for leaks. if that is all good let the system pressure out slowly and remove the tester.
next install the rad cap and run the engine up to temp. it will puke out what it doesn't need until it finds it's level so be ready for a bit of a mess. this is usually some point above the core end tubes if you happen to look in the rad when it is cooled off. now let it sit until cold again and recheck the level. after this it should not puke any more coolant out unless it gets really hot, like overheated. if you want to install a recovery tank try to get one that is from a system of approx the same amount of coolant capacity and you will also need to replace the rad cap to be a dual seal style.

[mach92bill]

Trouble is that with the design of the GMC filler you can't see down to the core.

[dsraven]

forgot to mention, water, although it will act as a coolant, is not the best thing to use in a cooling system that contains ferrous metals. metal rusts and scales the inside of the cooling system over time. rust is a good insulator and a badly rusted/scaled cooling system can give no end of trouble because the engine can't get rid of the heat it builds so the engine becomes prone to running hot and/or overheating under load. also, water has a fixed boiling point. coolant is designed to raise the boiling point, provide freeze protection and also contains corrosion inhibitors to slow down the rusting process. it is better than plain water but that doesn't mean it will last forever. the regular green coolant will last a couple of years and the long life pink or orange is rated for 5 yrs.
one other point, thermostats also don't last forever and if the system is giving trouble it may very well be a bad thermostat. I have taken many thermostats out and they have marks on the sides of the stat where one part rubs against the other part when the stat opens/closes and this can cause slow operation or failure due to sticking open or closed. I also will not replace a stat with anything but an OEM part, too many bad aftermarket thermostats that require me to do the job twice due to failure. if the stat has a little hole in it the hole goes to the top to assist with purging air past the stat.

[dsraven]

mach92, what rad do you have? my old 57 has the filler ight in the middle and the core is easily seen with the cap off, I think. it's been awhile.

[_Ogre]

i agree with roger, the top tank shouldn't be full, that is the expansion area
it worked the 1st 63 years of your trucks life, it should work for the next 63 yrs
probably should be filled until you see fluid in the neck

@dsraven i believe the 54 tank/filler neck looks like this from the top

[dsraven]

hmm, mine must have had a redo on the rad at some point. I am going from memory but don't remember that elbow in the neck. now I'm gonna hafta dig it out and look, haha

[mr48chev]

If you fill it until you have about 1/4 to 1/2 inch off coolant standing in the bottom of that 90 degree neck you should be good. That would probably be about an inch above the core. Or measure from the top of the core to a spot on the neck that you feel comfortable with an fill to that level. Just keep going back and checking when it is cold until you figure out that the level stays at that spot every time and you are good.

[mach92bill]

Yes, the pic that Ogre posted is about what I have. It's a GMC, which is a little different from a Chev which has the filler on top.

Based on all the replies, I'll leave it as is.

Still haven't figured out how to post pics yet.

[dsraven]

I see you're in Airdrie. if you need a pressure tester let me know. am in Calgary.

[MiraclePieCo]

An overflow tank can help compensate for a marginal cooling system by adding to the available coolant capacity. IOW fill the radiator to the brim and you've gained a couple of quarts of capacity, then let the recovery tank catch the expansion overflow.

[roger55]

Originally Posted by MiraclePieCo

An overflow tank can help compensate for a marginal cooling system by adding to the available coolant capacity. IOW fill the radiator to the brim and you've gained a couple of quarts of capacity, then let the recovery tank catch the expansion overflow.

Any coolant over the level of the core tubes will not add cooling capacity to the system.
That extra coolant will not be cooled by the radiator during the time it's over the core tubes.

[_Ogre]

if your looking for an overflow tank anyway...
i made mine out a 12'' piece of 3'' ss exhaust tubing

[bosco]

I agree, in the 70s my trucks were filled a couple of inches below the top and no expansion tank. My 96 tahoe was filled to the top with an expansion tank, with a low cold mark and a high hot mark. Never had to check it. Currently my 56 has a 98 sbc so we treated as a closed system with an expansion tank. Works great for my application.