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Re: Hot Water Heater Leaking Coolant
On cooling systems with an atmospheric catch tank, the radiator cap has two seals. The top one, which seals to the body of the expansion tank, and a lower one, which opens at 14 PSI. The excess coolant then runs into the catch tank.
On cool down, this is where a small sprung plate in the base of the cap comes in. It opens and allows coolant to be drawn back into the expansion tank.
Things that can and do go wrong are :
A kink or collapse in the hose between expansion and catch tanks, so water goes one way but not the other.
A bad spring or seal in the "coo down" valve in the radiator cap.
A bad seal on the radiator cap top seal
NB : all hose and other connections should be able to hold the lift pressure of the radiator cap. If not, either the connections, or the cap, are faulty. Ability to hold pressure is essential to proper cooling system function, as otherwise you can get localised boiling at hot spots in the engine, and generation of lots of gas.
I don't believe the exact height of the catch tank with reference to the expansion tank is important, as the system will generate plenty of suction on cool down. The expansion tank should be the highest point of the cooling system, though.
Bristol 31.1, San Francisco Bay
Last edited by MarkSF; 11-26-2013 at 02:26 AM.