Michael,

The reason I was running with 100% antifreeze was because I had been running the trooper in the winter with a failing head gasket. I could tell that the gasket was leaking from the white smoke out of the exhaust. The freeze plug popped out AFTER the gasket had already started to fail. Who ever had the trooper before me had changed out one of the freeze plugs with an "aftermarket" freeze plug. The kind that are rubber and that expand when you tighten the bolt.

That freeze plug is the one that popped out on the freeway. I found it sitting on the motor mount after having the trooper towed home. When I replaced the freeze plug that had popped out I ordered the "factory" (metal) freeze plug from Isuzu and installed it in the engine block. I tapped it in with a socket and a hammer. I suspect that when the freeze plug popped out it killed the head gasket and more than likely cracked the head.

I only hear the "poping" when I am checking the compression. It is at "starter" speed. I only hear the poping when I have the compression gauge screwed into the spark plug hole of each cylinder. If I unscrew the compression gauge and have all the spark plugs out of the engine and then "spin" the engine I hear nothing wrong. Just the normal "spinning noise" of the engine.

The "poping" noise that I am hearing is like a loud "passing gas" sound or like a balloon poping. It is in rhythm with the turning of the engine.

I ran the trooper after I replaced the freeze plug for about 2 months before I had to take it off the road. The "smoke screen" that the trooper was creating was getting too bad to drive the trooper safely.

What are the symptoms of a cracked engine block???? Would loosing the freeze plug on the freeway cause the engine block to crack?????

I chased out the head bolt threads in the block with a tap. I even ordered new factory head bolts from Isuzu.
What could be possible causes for this problem????
Thanks for the help.

Mike