Jeep “overhearing”

[Swindle]

So new problem with the 4.0 swap. Temp gauge says engine is at 250 (new autometer) engine starts coughing at about 200 and dies at 250. I pulled the thermostat thinking it might be stuck and no better. New water pump and coolant is flowing. After overhearing oil is cold which is odd. All Plugs come out black every time I pull them. No oil in coolant, no coolant in oil. Any ideas?

[calvynandhobbs]

I'm just thinking out loud here. Is it the correct water pump and is it flowing the correct direction.  I don't remember where I heard it, but I have heard of this happening before.  Just can't remember if it was Jeep or another type of car. How quickly is it overheating? Is your oil pump working or is the oil just sitting in the bottom of the pan, which is causing the overheating?

That's all I can think of right now.

[Swindle]

As far as I know it’s the right pump. All bolt ons are for the 96 xj engine. Oil pump is new and I previously had a valve cover leak while running so oil is getting to the top. Based on the short time it takes to “overheat” the theory is that it’s trapped air that is heating up and not the coolant. Eng temp at initial start is over 100f. Approximately 2 min later it climbs to 200f and starts coughing. Approximately 2 minutes later it reaches 230f and coughing increases. At approximately 5 minutes temp reads 250f and eng stalls. Only air can heat up that quick and the gauge temp sensor is inline at the upper radiator hose. Most likely I have a clogged water jacket causing air to get trapped. The engine sat open for a long time and the radiator sat open all winter. Mickey might have opened a new clubhouse in either for all I know. I’m going to try a radiator flush tomorrow night and hope that gets it. Without a thermostat installed it shouldn’t overheat in about 5 minutes of idle time.
Just the latest theory in along list of problems with this conversion....

[Swindle]

I flushed the engine and radiator this morning with a flush kit and nothing came out of it. No rust no deposits. Nothing but clean coolant and water. Ran it for an hour with garden hose attached and it ran fine. 20 minutes of burping and it hit 250 and died. Any suggestions because I’m about ready to call it quits on this engine?