Just acquired 94 Explorer, V6 4.0L I think, that has built up too much pressure in the cooling system and blew out the freeze plugs, also has small engine knock. I am a tax accountant, and client who owns repair shop had vehicle come in for repair, he replace freeze plugs and they blew out again, said customer could not afford repairs, so I bought from customer. Mechanic says best thing to do is get another engine from a junk yard. Mechanic is a foriegn car specilist and does not like messing with US cars. I am just wondering if current engine is not salvagable, cheaper than replacing with junk yard engine that you still are not sure what you are getting. Have had people tell me may be clogged radiator, or blown head gasket? I do not have a clue! Oil is low, but does not appear to have any water in the oil. Any diagnostic help would be appreciated.

Thanks / Mark