[pairodice]

The overflow tank is up to the full line with antifreeze, the hose looks to be in good shape but the cap is spewing excess when I filled the tank two days ago.  If I completely fill the tank up (I pushed a finger in so the cap had some room) should the cap allow antifreeze to escape once the tank heats up?  The unit is heating up over 200 degrees but we can smell antifreeze from where it is escaping from the cap.  Should I replace the cap?  Is this something I can get at NAPA?  Anyone got a part number please?

[Trainer]

The heater tank should be full to the filler neck. Radiator cap is 13 lb at all auto part stores. The overflow system, filler neck, radiator cap, overflow hose barb and overflow hose with 2 clamps should be air tight -- NO leaks.

The level in the overflow tank should go up as the heater heats up and down as the heater tank cools.