Recently my wifes 92 has developed some issues. I noticed the other day that there was air in the coolant system because I heard a gurgling sound in the dash (like a water fall). Coolant was low but no signs of fluids mixing. I know in my supra un-purgable air in the system is a sign of a bad head gasket. This explorer has 194k miles on it and a fresh rebuild on the A4LD, like 1 yr ago, about 5k miles. It has a bad lifter as well. I am going to do a block test and a compression test this weekend. How strong is the bottom end on this motor? It does not burn much oil. If I fix the top end will the bottom end blow up? Are head gaskets a common issue? Should I just replace the gaskets and leave it at that? Should I drop a used motor in it? Its my wifes and she does not drive it much, but it needs to be reliable for my kid. What would you do? Thanks