2000 Cherokee overheating issue
 

I have replaced the thermostat now already and still doing the same thing. Also I have checked the coolant fluid level and thats okay.

After 10-15 minutes of running its sitting right around 210-215 without issue. Then out of no where it just shoots up to 250 and the the warning light comes on. I do not have any leaks either.

What could be causing this? Sensor?

Could have a cracked head, 00-01 are known for it. Is coolant disappearing? Milky oil? Oily coolant?

coolant is not going away. staying level.

The first 2 times this happened I was not in a spot to stop and 15-25 seconds after the light came on the warning light went off and everything was fine. 3rd time its been sitting since. I just replaced the thermostat today

sure the water pump is good? they tend to corrode away. my son had that issue.

E-fan coming on at 210 ?

yes fan is coming on.

I have not considered the water pump. I have never had one go bad that I know of without the plug going bad and leaking.

The infamous 0331 head cracks in the 2000-2001 years typically do not cause overheating. They cause coolant to go into the oil which will wipe your bearings if left unchecked.

Typically overheating like this will cause coolant to pour out of the coolant reservoir. The sensor could theoretically be bad, but its not common. A sticking thermostat, air in the system, or problems with the water pump, radiator, or radiator cap are all more common. The head could be warped or the head gasket blown (or both).

I will say that you probably do need a new head at this point or will shortly. Factory original 0331 heads do not tolerate overheating and are much more likely to crack after just one overheating episode. Remove the oil filler cap and look straight down. That is where the common crack occurs. You will see raw coolant, a crack, or "tan lines" if the head is cracked there. Keep an eye on it even if you fix this problem without pulling the head. And if you do pull the head, replace it with something from Clearwater or a remanufactured TUPY.

I had considered the head, but I have not lost or gained any fluids on any end.

I am going to try to bleed air out.

What gets me is when the warning light kicks on. I can shut it off and restart within 1 minute and it will run another 10 minutes before it suddenly shoots to 250

The easiest way to do that is to take the upper radiator hose off at the thermostat housing. As a point of reference, if you drain the radiator from the petcock or by removing the lower hose, it should take about 6 quarts, then add about two quarts to the jug (to FULL). After a couple of hot/cool cycles it should drop to ADD.

I use only dealer thermostats because they always work and have the jiggle pin.

Do yourself & your engine a favor and keep checking that head by removing the oil filler cap though. These heads are notorious for problems and if one is on the edge a single overhead can crack it.

Before jumping to too many conclusions, grab an IR thermometer and see what the actual temperature is, particularly if you aren't getting other overheat symptoms.

The gauges in later years are screwed with by the PCM. At a certain temperature the PCM trips and slams the temp gauge needle full-right to get your attention. All bets are off on what the actual temperature is.

It could be a clogged or bad heater core it could be the radiator or water pump or even the fans clutch.

2000 jeep cherokee sport 4d 4x4
 

I have the same issue ive change the head,waterpump,radiator,rcap,thermostat, i dont have a shroud over the fan clutch but i would get off the highway and it would overheat so i figured its either the shroud or fn clutch .today i just took fan clutch off and screwed two self tapping screws threw it on each side so its still balanced the screws keep it engaged all the time just so i can see if it was the fan clutch gradually going out .picknpull tommorow for shroud and i have the bank 1 sensor 2 sensor to replace hopefully its just the sensor. We will see if i start to overheat or not.

Does anyone no if theres any way air can be sucked into the coolant system through anywhere i think it would spray out but u never no i might just be impatient when waiting for the bubbles to stop coming out of the radiator.?

Before i replaced the head it never overheated but the head was cracked 6different places only between the cylinders so there wasnt. Much compression my new head is thicker were its known to crack.

the impeller was wasted on my sons 4.0 twice. the pump didn't leak either time... first time it ran cool all summer long and it was a hot summer.. then winter came and it started over heating in 20* weather.. after some reading on the different forums and seeing that youtube video i figured it was worth a try to look a the water pump.. sure enough the impeller was flat just like that video.. not sure why but these motors really seem to eat water pump impellers if you do not use distilled water..

I have run the truck again this morning and the upper hose was warm. would not say that hot but not very firm. I could easily pinch the hose.

I can not remember if that should be super firm or not.