This is for a 93 subaru legacy coupe, automatic. AMA (against MY advice, i.e., I am the (so-called “wise” (interfering), “experienced” (know-it-all, pompous) (you pick the correct adjectives) father; the impatients are my son & his girlfriend, both early 30s), they decided to buy this car for a 1-time-only cross-country trip (~4-5 K miles) in 3-4 wks. rather than rent a car & pay the higher fees to leave it “there” (end of the trip, which ain’t here), & sell car for some bucks back at end of trip. They decided to save further $$ by not paying the extra $50 or so for the shop to add a compression test to the checkup of the car, & declined for me to test it (yes, I rebuilt my cars for 14 yrs. or so in my own foolish youth, & still have all the tools/scars to prove it). So within 20 miles, after they bought the car, it checking out ok, including radiator, oil & electronics, it blew up literally – a blown head gasket, which AAA (yes, I bought it for them as a parting gift/warning) tow person said the pre-buy check could not have foreseen.
I think that while a compression check only sees low compression per se, it might have spotted this problem. But I’ve never thought about the direct connection much. I never had a blown head gasket on my cars, replacing whenever I opened the engines. I know uneven compression may indicate an already failed head gasket, but what about a compression test foreseeing a head gasket failure that has not yet happened? I also know that uneven compression is of course in general a very bad sign & if I had seen it I would have said “no” to the car. But what if the readings were low but even, as specifically regards head gasket? (I did look thru a few pgs. here before posting, but didn’t see a direct answer.) Thank you.
FYI, they did rent a car after, & continued happily enroute.