98 Classic

Bought it last night on kinda a spur of the moment thing but didn't get far before the temperature gauge flew to the right side. It was in the center when I watched it just jump straight to the side and "Check Gauges" light came on. I don't have any steam coming off it, over flow isn't even dripping, puzzled though because the top hose has hardly any pressure.

I am here asking this simple question because I don't have a lot of experience with closed cooling systems like this one. Any idea other than standard thermostat, water pump, temp sender that I may be missing?

Thanks yall

 

start with the thermostat.

 

I'd say lets start with the basics. Did you check to make sure the coolant level is correct? If it's low, just add some original green and then check for leaks. If the coolant level is correct, what color is it? Is it green like it should be or is it red and rusty looking, which indicated a flush badly needed. If the coolant level and color look fine, then I would go ahead and check your thermostat. It's very easy to check. Follow your upper radiator hose from the radiator and where it connects to the engine you will find a couple of bolts. The thermostat is under there. Carefully remove the bolts and pull the thermostat. Make sure to pay attention to how it was in there because if you put it in backwards, you can blow the engine. Get a small pot of water boiling on your stove. When its got a good boil, drop the thermostat in. If it opens up, then your thermostat is good. If it doesn't open completely or at all, then you need to replace the thermostat.

Remember to always let the engine cool before checking any component of the cooling system. Failure to do say can result in anything from minor to major burns.

Good luck and keep us updated.

 

my overheating issue this summer was caused by a bad fan clutch. On highway it was just fine but as soon as I got to the lights, the temperature would start rising. Don't just check the t-stat, replace it. Its 5-10$. radiator cap, this is responsible for metering the overflow and adding or removing overflow, 5-20$. top off the fluids, check if there is rust in the radiator coolant. Check the loose in your fan clutch. if there is alot of loose then its your fan clutch. If not then its your waterpump.

before you do all that, check for leaks...if you haven't checked.

good luck.

If none of that works, then its because the coolant has lost its cooling properties either because its burned out or really dirty. Flush the whole system and put a new mix of water and prestone.

 

Coolant level is just fine, we messed with it some last night, I burped some massive air bubbles out of it, guy I bought it off of just had a new radiator put in 3 months ago with new fans. Everything was nice and green. I'm heading out to tow it home in a little bit, ill be able to tear into the thermostat then, I live an hour north of where I bought it and didn't want to risk trying to limp it home only to crack the block or blow the gasket. This XJ is in really good condition mechanically which is why I'm a lil miffed but hell if its just a thermostat or a bad sensor then I can't complain. I'll post back in a little and throw out an update.

 

And were good, Thermostat the last guy put in was rediculous, it was a JDM 215 degree, who the hell puts a thermostat from a mitsubishi, with such a high heat threshold in a jeep? Thanks to all who answered.

 

doesn't make sens to me but people do bizarre things.

 

Wow, that's a first. Nice to have an easy fix. Assume you replaced it with a 195?

 

Interesting, I just had mine overheat tonight and they had a 195 in it, that seems too high too, I think I had a 165 or something in the one XJ and it rarely gets too warm. Time for a new thermostat for this one though.

 

The 195 degree thermostat is what the 4.0 is designed to run with, and is absolutely the best choice for the vast majority of applications.

 

mine runs all the time hot or cold outside at 215, right smack dab in the middle of the gauge. is this too hot? 2001 4.0

 

The "target" temp for the 4.0 is 200-210.

There can be some inaccuracy between the sending unit and the gauge. Because of that, you should really take the time to confirm your coolant temp.

Get an infrared point and shoot thermometer (widely available anywhere). Point it directly at the thermostat housing.

Then you will know exactly what your coolant temp is.