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Hey everyone I'm for some help!

I have a 1993 Isuzu Bighorn with a diesel 3.1L 4 cylinder 4JG2 engine, it's an indirect injection sleeved engine. I have posted on a few Isuzu forums and haven't had much luck, looking for some general engine advice from y'all.

I was on a road trip when my coolant hose exploded, took me a min to see/smell the car was overheating. The hose for the oil cooler coolant gave out and I noticed the thermostat was clogged and the hose was just old and brittle. Replaced it with some new hose and got rid of the thermostat. After fixing everything I noticed the car would leak a lot of coolant from the radiator cap/overflow and I would have to refill the coolant a lot.

Exhaust in the coolant lead me to think I had a blown head gasket. Got one in and got everting apart, had cracks in between each of the cylinders valves. Had to reassemble everything with the broken heads. Also had the oil tested, no water, diesel, or high metals.

Ordered a brand new head kit. Got everything fixed up. Drove the car to work and the temp jumped up, almost hit the red. Pulled over and let the car cool off, filled up the coolant. Assumed I forgot to fully fill it up and when on my way. Happened again on the way home, lot of pressure in the coolant system.

Thought, maybe the exhaust going through the turbo was leaking into the turbo coolant, looped it off, and still getting pressure. So then I figured I had a cracked sleeve causing the exhaust to get in the coolant. Did a compression check and they are all at 380 psi +- 5 psi. That makes me think the head and cylinders are good. A friend said maybe I have a warped block.

Also, a friend said maybe I have a warped block. The pressure in the coolant builds up a lot faster with the new head compared to the old head so I could see the block or head potentially being warped. But at the same time, the compression for all the cylinders being +- 5 psi makes me think it could also be fine?

Where else could this be coming from? I'm so lost and out of ideas!

Automotive parking light Automotive side marker light Tire Car Wheel

Gray is the broken one, Green is the nicer replacement!
 

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I am not familiar with this engine at all. Having combustion gases going into the cooling system seems like it would have to be head gasket related but I agree that the high compression doesn't reinforce that theory. Exhaust gases after they have left the combustion chamber wouldn't have enough pressure to force into the cooling system, and this train of thought puts me right back to the head gasket. The engine block may have to be decked to get everything flat to hold a gasket. Sorry I couldn't be more help.
 
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