im not a pro., but if u dont understand the purge , what it does and how it works, let me suggest more reading., but to try to answer ur question,
like u said , exhaust solenoid, solenoid is electrical the valve has a seal.,
if seal is compromised , yes i am assuming that air will be pulling in and hopefully pulled back out with the purge.,
., if there is excessive purge, time to find leak.,
isolate chiller.,
adjust water lever in chiller., create a positive pressure.,
tighten all flat gaskets., and if still excessive purge., well , lets see if the true pros add in.,.,
MY QUESTION IS when does someone know it is time to change exhaust valve?