was the head removed? for a gasket replacement?

Is so you should have checked it for straightness, with a straightedge and a feeler guage. also, it wouldn't have been a bad idea to have it pressure tested (for cracks) and vaccum tested (checking seats).
most auto machine shops can perform these services for you for a resonable fee.

you need to determine wheather you are losing coolant or not. does the system build pressure? carefully check the rad cap after a run in which you reach full operating temp.

if it blows white smoke under load, then you probably are burning coolant. a comp test doesnt reach the same pressure as combustion.

the car isnt the problem.