I've got a new head on my 2000 XJ due the usual cracked head and overheat problem. Everything done right: good gasket, new bolts torqued properly, etc. But now the motor runs very hot-- way over two-thirds towards the right on the dashboard gauge. Even when things were going bad, the temp indicator rarely went past the vertical halfway point. Any ideas from the group?

Separately, my electric doorlock doesn't work after disconnecting the battery for the cracked head replacement. The dashlight also shows a diagonal line across the key icon. Is there a simple reset? (I'm getting old...)

For what it's worth my Cherokee Sport has only 190,000 mi in a mix of of light routine use, some interstate highway driving, and occasional rough offroad timberland in 4L.

 

What else was done in addition to the cylinder head job? Like water pump, thermostat, ect?

 

I would ensure that the system is filled with coolant thru the radiator so that an hot pocket of air isn't giving you this reading. Is the radiator full, the reservoir? Report those statuses first before checking other things.

 

The temp sensor may be bad from the original overheat when the head cracked and is giving you a false reading. Try using an infrared heat gun on it and see if there's a difference.

 

I'm thinking there is air trapped in they system. I agree with the infrared temp gun idea to find out where the temps jump.

 

it has to be air and yes double check with a temp gun the sensor might be fried or rather boiled did you get your new head trued up skimmed shaved ? I was told when I freshened up my head last year and I did it to run for the first 100/200 klm on fresh water when the engine gets up to temp turn the heater on flush the system and apparently the water helps the gasket bed down before being exposed to the harsh coolant ? old wives tale? did it anyway as I have 390000 klm on the clock after the water flushing I emptied it all and used low pressure air to get all the water out drop bottom rad hose fill up with coolant and run heater on rad cap off until all the bubbles are gone I hope it is only needs Burping!

 

There is a procedure to "Burp" your cooling system. I think it goes something like this. Get a funnel that will make a good seal in the radiator cap opening. Start the jeep. Heat on high. Put the funnel in fill hole. add water filling the funnel. Squeez upper rad. hose, (be careful of fans.) You should see bubbles coming from the funnel, keep adding water/coolant. rev engine, add water as necessary. be careful as the engine heats up thermostat may open and water will come out of the funnel. you should be done before this happens. If it does happen to remove the funnel and replace the cap. Make sure the reservoir is full. You may have to repeat.

 

Okay, here's how I do it. Remove the temp sensor from the thermostat housing and fill the system until it runs out of the sensor hole, install the sensor then continue filling it. After startup, you may have to add a little, but not much. This works with any 4.0 without a heater control valve. The heater core is wide open all the time so coolant will fill it weither the heater is on or off. Fill the reservoir about 1/2" above the full hot mark and any remaining air will drop it to full.

 

Thanks, everybody
I had remaining problems that needed to be solved. First, yup, the system needed to be burped. So my appreciation goes to having it pointed out. Second it needed a new sensor, so again I appreciate the suggestion. The infrared scanner identified something else too: cold and hot spots. Turns out about four years ago when I was out of the country all winter, the expansion plug went at below zero temps. The mechanic with whom I'd left it fixed it and also added a helluva lot of stopleak which eventually -- last week -- clogged the radiator. Repeated flushing kept pushing out more sludge. Eventually I just put in a new radiator. So far, so good.
The test is next week: A full day run on the Interstate to the woods, then miles on a right-of-way across wilderness forest to my own timberland in 4Lo. If I don't overheat I will know I'm good. Watch for a report. Take care.

 

Hey Dude! Where you at? My XJ came from Camden!