New XJ owner.

Had over heating problem' XJ low on fluid.

Flushed cooling system. Burped it.

Changed thermostat, replaced malfunctioning aux fan.

Ran for awhile. Coolant flowed back through radiator cap until... it didn't anymore. Maybe there was more air. Maybe I overfilled it.

Ran between 210 and 220 for a few days.

Today I ran it and "check guages" light came on and temp spiked to 260 in the red. Let it cool. Started it. Check guages light came on temp showed 240, then light went off and temp dropped quickly to 210-220.

Ran it some more and light came back on and guage spiked to 260. No overflow, no bubbling, and coolant cap was not hot to touch.

Any ideas? Thinking about radiator change... then water pump.

 

That part makes it sound like a sticking thermostat. Might also be the water pump.


I've never run the numbers myself, but many on hear have said you can pretty much replace the entire cooling system for around $200. That's not a bad idea.

 

how quick is the gauge spiking to 260? like climbing fast or just it actually jump like the gauge was sticking? if it jumps i would suggest a new coolant temp sensor for the gauge.

if you have a digital thermometer you could verify the actual tempature

is it a clutch fan or electrical fan?

 

Verify temps at the engine coolant temperature sensor housing with an infrared thermometer. I agree with BlueRidgeMark that it might be a stuck thermostat, but I have noticed with my 98 that the sensor gauges will report in the 210-220 range up until at least the 250 mark. I have a scangauge constantly monitoring temperatures as reported by OBD2 and I've seen my jeep get up to 248 while my instrument cluster happily reports I'm a touch over 210. I was able to pull over and verify the 248 was correct with that IR thermometer.

 

That's good to know!

 

I'll second this- gauge acts more like an "idiot light" between 210 and 240.


If it's a quick twitch of the needle you might also look at the wiring for your temperature sender. Maybe it's grounding-out somewhere?

 

Spent some more time on this... don't think it is the temp sensor since boiling in the reservoir persists after flush, burp, and refill.

The thermostat is brand new. Not likely sticking (right?) ... and same symptoms persist.

I plan to replace the radiator... and if that doesn't fix it ... replace the water pump. Lots of info on here about recommendations for rads and water pumps.

I am TRYING to not just "throw parts at the problem".... have a multimeter and an IR sensor now.

Thanks for all of the input... love this vehicle. This is actually my son's XJ. I enjoy fiddling with it so much I think I'm going to buy myself one.

 

What brand t-stat are you using?

 

$8.00 t-stat from AutoZone... can't remember brand... threw away the box. It definitely wasn't MOPAR.

 

That could be part of problem, those cheap t-stats have a decent failure rate. Just about every elder/heavy weight user on this forum will recommend you get a MOPAR stat. They are high quality with a low failure rate. Stant would be a second choice.

 

All,

Based on some input received I checked the temp with my new IR thermometer.

I'm pointing it right at the area where the temp sensor seats. I'm running true temp between 245 and 250. This answers a lot of questions as my gauge has been hanging at 220 and then spiking to 245 for a short time then dipping back to 220...

Conclusion is what many of you already said - gauge swings dramatically when true temp only swings a few degrees.

That said, this is still running hot after I've done the following:
1. Flushed coolant
2. Burped system
3. Installed new t-stat TWICE... currently running a Stant Superstat 195 degree
4. Installed new fan clutch
5. Installed new electric fan
5. Installed new radiator

Next steps unless you guys give me a better idea:
1. Change water pump
2. Check head gasket....

Thanks
Russ

 

checking head gasket with the block tester is not a bad idea and doesnt cost much 30$ for rent and 10$ for the fluid you get the 30$ back.. at least you will know if it is the head gasket or buying a new water pump for 40$

marc

 

What happened? I have the EXACT same experience and I did a block test with no sign of a head leak. Shrugging over here.

 

The OP appears not to have been on the forum since Sept 2019 so I doubt you'll be getting an answer about this....