Antifreeze smell
Sometimes the hose from the radiator to the tank will deteriorate and leak, especially if the battery leaks and corrodes the hose, as it runs right under the battery.
1 of 12 possible anwers, LOL.
HTH,
GWJ
the likeliest culprit; the engine temp will be above
boiling and burp coolant into the recovery tank
once the engine quits running and the heads
unload the rest of their "pipelined" heat to the
water jacket (now stagnant).

