Went out to start my truck today and nothing but a "thunk". I was unable to turn the motor over by hand, however it would turn backwards. I heard from a friend that the 1997 4.2 was notorious for leaking head gaskets. Can anyone give me some info on this subject and what is the best fix?

 

The first thing I would check is your oil. If it has a milkish look, it has water in it.

Also, you can run your plugs out and see if it will turn over. Based on your description, it almost sounds like a cylinder was full of something which would not compress, which would account for the thunk as the cylinder was comming up on compression, and also it would allow you to turn the engine backward as you would be moving back into the exhaust cycle.

Best of luck

Larry

 

Were you able to get her to crank after backing it up? If so, did it sound like a blacksmith was under your hood with a hammer? I personally know two people that have had connecting rods fail on their 4.2. With a leaking cylinder head, you should still be able to crank it, but if it's a rod, cranking it will score the engine beyond repair

 

Was able to crank it after turning it backwards, but it stopped at the original turning point.

 

If it's a 4.2L: www.leakingfords.com

Don't try to start the engine again while it's hydro-locked and you may get away with just replacing the gaskets, rather than the entire engine.