JickRones

*2001 Cherokee Sport, 185K. Yes it does have the inferior 0331 head but I have not seen any signs of a crack.

Just recently purchased this jeep, was driving it a couple weeks ago and noticed when I got back home the coolant was bubbling and hissing out of the radiator and into the overflow. So the next day I pulled it into the garage and let I run from cold and after about 25 mins the temperature had gotten up to about 250 (I was reading the temp live on my scanner) and overheated.

Since I had just bought it and wasn’t entirely sure of the condition of all its parts, I decided to replace everything. New radiator, new water pump, new head gasket (old one looked fine), new hoses, new thermostat and housing, new fan clutch, also I bypassed heater core for now because it seems to have crud in it.

Now that all the cooling components are replaced I filled up the coolant (used spill free funnel, waited for t-stat to open then filled it up more and closed the cap). Figured the best way to test the system is to have it idling in the garage (85 degrees and poor air flow) with AC on full blast with the electric fan disconnected. Using my scanner I read the live temperature and this is the results:

175F after 5 mins
205F after 10 mins
221F after 15 mins
231F after 20 mins

At that point I shut the engine off because I don’t want to keep it running that hot (especially with the 0331 head). Also the hood is off this whole time.

I haven’t taken it out on the road since replacing all the parts, and I’m sure it would be fine driving down the highway or whatever. I know idling in a small garage for 20 minutes isn’t ideal, but I also feel like it should not be getting that hot if everything is working correctly. And the electric fan is unplugged but I also feel like theoretically the fan shouldn’t be needed with everything working correctly. Hoping somebody has some thoughts on this, obviously there’s lots threads online dealing with overheating issues but I’m at a point where I can’t seem to come up with any more ideas. I also am not fully accustomed to this vehicle and all it’s quirks yet.

also one more note, even though my reader device is saying 231 degrees the gauge on the dash only has the needle at about 212.... no sure if that’s just an accuracy problem with the gauge.

bluejeep2001

The 2001 will kick on the fan usually after about 10-15 min of idling if your lucky...its usually faster than that...the clutch fan alone on a non-moving jeep will not keep cooling enough to keep the temps below 225...the fan will come on...sender/ computer turns it on at around 220-225. In 85 degree weather there is no way to keep it cool without the aux fan especially if the ac is on

boxburn

I'd suggest plugging the fan back in and see how your readings go. There are also 2 coolant temperature sensors so you could find a difference in reading between the 2 giving you 2 different temperature numbers.

With the AC on, the electric fan is signalled when the AC needs it, which is also when the engine is under extra load.

dave1123

On the 2000-2001 models, there is only one temp sensor and the computer decides when to turn the e-fan on. It also sends commands to the gauge telling it what to display. Everything displayed on the cluster is sent there by the computer, not from sensors. I suspect even the oil pressure and fuel tank readings are also, but I'm not sure. I DO know the oil pressure sensor has a chip in it because I broke one taking it out.

boxburn

Oh. I'm sure the diagram listed 2 when I looked yesterday.

dave1123

Hey dude, any time I state facts, they are only what I'm reading in my FSM for the XJ. I haven't had eyes on or hands on some of this stuff, but going by my WJ, which I know intimately. It took me quite a while to learn things are hotwired and the computer controls them by switching the ground circuit. It blew my mind when I learned even the gauge displays are from the computer and are not directly connected to the sensors! Also the computer output is either on or off and anything in between is a pulsed output, as in square wave voltage.

I only recently found out how the computer knows which cylinder is #1. The CkPS window in the flexplate is a different size and creates a different pulse. Freaky!


Near as I can tell, there are only 2 temp sensors in the diesels.

bluejeep2001

Dave 1123 is correct post 96 only have 1 sensor in the tstat housing it feeds the computer for fuel scheduling and temp sensor readouts and aux fan control... therefore there is no way to check its accuracy at higher temps directly . In the morning when its sat all night and the engine is the most equalized to ambient, you can take your OBD2 reader scanner and compare air inlet temp to coolant temp..they should be the same within a degree or two, but again that does not confirm accuracy at hot. I don't trust temp scanners that much just because I don't know exactly how they work..I guess if you point at a pot of boiling water and it shows about 212 you can confirm its accurate. I don't have one so I took my sender out and hung it in a pot of boiling water and read its resistance with a Fluke meter..read 675...about center on the printed charts. I then used my decade resistor box and pumped in a 675 reading into the sender connector on the engine side..gauge reads 210..close enough for me..disclaimer...early 96 and earlier have 2 sensors.the cutoff varies to when your jeep was actually built

boxburn

I was right with what I saw, just wrong with how I read it. Coolant temp #2 is on the Diesel page. It's only listed as #2 to differentiate itself on the component list from the gas version.