2nd-ing " Its expensive to fix so start socking away for new transport."
The classic case # numbers wise, I needed $500 rear brakes + $500 front axles + $700 torque converter, just to keep a Subaru on the road, not counting State Inspection or overheating or busted A/C system. But I traded the car in for ~$700 and came out ahead on the deal ; way ahead.
PepBoys and similar, have a complicated but do-able Goo that "repairs head gaskets".
In other words, you might get it to work, and just long enough to unload the car.
Good idea to do full disclosure when selling
= "IDK WTF I tried this stuff it seems to work maybe you can fix it"
... As someone who has had similar problems ...
Yeah I've blown a head gasket too.
figuratively and literally