Need opinions for using a Moon style Aluminum fuel tank as a radiator expansion tank mounted low in front of the grille. I want one for my street legal 36 Chevy g***er and rather than just sticking it out there for looks I thought about making it functional as a radiator expansion tank. Of course it will be much lower than the radiator cap and the one I'm looking at has a vented cap so that would have to go. What say you all ?
It may have been done before, but that doesn't make it a good idea, IMO. I'm not a fan of Moon tanks on street cars to begin with, using it for a radiator catch tank seems kind of along the same lines as sticking Cadillac or Oldsmobile valve covers on a SBC; or multiple carbs with only 1 of them actually functioning, or a fake quick change cover. JMO.....
Use a radiator cap designed for a recovery tank. Run a line from the Over flow to the bottom of the Moon Tank. Leave the top hose on the Moon Tank open to act as a vent for the water coming in at bottom. You can hide it on the back of the Moon tank. Works Great. I have used the Moon Tank for a recovery tank on several cars. Jerry from North Carolina.
It doesn't matter if the cap is vented. But a Moon tank mounted low in front will only work as a catch can, not like a normal coolant recovery tank. So every so often you'll need to top off your radiator, and drain the coolant that overflows into the tank. I put a small pet**** on the bottom of mine to make draining it easy. Just check the radiator as you would on any vehicle that doesn't have a recovery tank.
If you plumb it as I said It works just like a normal coolant recovery tank. You MUST use the proper radiator cap for a recovery system.
If the overflow tank cap ain’t vented, it will pressure up to radiator pressure. If that little Moon tank ain’t rated for the pressure, a kablooie will soon follow. For a recovery system (or non-recovery fir that matter) the overflow tank can be as low as you like in a car. As long as the hose tip is in the recovery tank bottom, it will draw fluid. The cooling engine/radiator contents draw a mild vacuum to “recover” the “expanded” fluid back from the recovery tank, uphill into the radiator. To make it too low, you would need it to **** about 14 metres uphill. At that point, you need so much vacuum that the water boils at room temp, and won’t draw back. (my 14m may be out by a metre or too… my fizziks is getting rusty). Cheers, Harv
Mooneyes makes several styles of radiator-related Moon tanks. From their website: https://www.mooneyesusa.com/product-p/mp1007w.htm https://www.mooneyesusa.com/product-p/mp1008s.htm https://www.mooneyesusa.com/product-p/mp1008w.htm
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