1998 Cherokee 4L jumps from 210 to 260 very fast

[rpfelder69]

After I installed a new radiator in my 1998 Cherokee 4L I blew the head.

It sat up for about 10 months. I installed a rebuilt head, changed out the thermostat and radiator cap, and had the radiator flushed out.

The engine runs for awhile at 210 or just above it for a few miles and then sky rockets up to 260. I noticed that all of the hoses have very high pressures and almost immediately after cranking the engine that antifreeze is pushed into the overflow bottle.

What could possibly cause this to happen?

 

[Evan]

Maybe the head gasket was installed backwards. Is that possible? It could potentially cause the symptoms you're seeing.

 

[Saurian]

For reference, I was informed that the gauge on the XJs is not quite right... It sits there, innocently just slightly above 210, and you think all is well, till it blasts up to 260. The engine is not just suddenly going up 50 degrees, for some reason, the gauge does not register that range; instead of sweeping up, it hangs at 210 till it gets past the overheat mark.

As far as initial cause, I can't help you there; it's been four years or so since I sank mine in the mud, and it's still running a teeny bit warmer than I would like it to be... Then again, my radiator is 8 years old...

 

[rpfelder69]

That makes sense. I actually got the engine running one mark below 210 now. I took the bottom and top radiator hoses off and stuck a garden hose in the radiator and flushed it out. Then I covered the bottom hose to make the water flush out of the top hose. I flushed the block out too. I also flushed the heater coil out with the engine off and heater blowing. I had a ton of junk in the cooling system causing me to have little to no circulation.

Once I did that I've had it running below 210, except on very hot days then it runs just above 210 but not past the next mark.

For reference, I was informed that the gauge on the XJs is not quite right... It sits there, innocently just slightly above 210, and you think all is well, till it blasts up to 260. The engine is not just suddenly going up 50 degrees, for some reason, the gauge does not register that range; instead of sweeping up, it hangs at 210 till it gets past the overheat mark.

As far as initial cause, I can't help you there; it's been four years or so since I sank mine in the mud, and it's still running a teeny bit warmer than I would like it to be... Then again, my radiator is 8 years old...