4.0 zj coolant issue

NCJeeplover

NCJeeplover

Well-Known Member
Joined
Jul 25, 2009
Location
Claremont, NC
A little backstory on the jeep. I bought a 1998 2wd 4.0 Jeep Grand Cherokee for my wife as a beater. I picked it up cheap because it had a coolant leak. Turns out the freeze plug in the back of the head had a pinhole in it. Pulled the head and replaced the plug. The coolant seemed really dirty and parts are cheap, so I replaced everything water touches except the heater core (all hoses, radiator, water pump, thermostat and housing, everything!). Jeep ran good and we have put probably 30k miles on it over 5 years or so.

Fast forward to the end of last year. I started to notice a small wet spot under it on the driveway when parked. Checked it out and it was coolant. Pressure tested the system and it held 15psi for 30 minutes. Did some more digging and turns out the radiator cap was leaking. Picked up a new cap and the leak continued. Thought maybe the cheap parts store cap was bad. Bought a good cap to replace it. Still leaked. Then it started to run a little warmer than normal (215-220). Then it started to run rough and when you turned it off bubbled pressure in the reservoir.

I pulled the plugs and did a compression check thinking maybe the headgasket was bad leaking compression into a coolant passage.

Cylinder 1 - 135
Cylinder 2 - 125
Cylinder 3 - 110
Cylinder 4 - 140
Cylinder 5 - 150
Cylinder 6 - 150

Now I'm really confused. Compression seems to be all over the place and no obvious "dead" hole. I'm not sure how to proceed. I was truly expecting a dead hole and to put a gasket on it. What would be the next thing to check?
 
One more thing to note, when I would release the pressure from the coolant pressure checker it would blast coolant everywhere. I've never had one do that. Even if I tried to just barely bleed pressure off coolant would come through the pump.
 
just bring it and a case of beer over to the house....I'll watch you replace the head gasket .
 
1stgenxxx said:
just bring it and a case of beer over to the house....I'll watch you replace the head gasket .
Click to expand...

I was gonna say, Ill bring mine and some beer over to his house, and can replace them both at the same time.
 
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