magpulcherokee44

I have a 99 cherokee sport that is having issues with its temp gauge. It will stay at about 210 most of the time, then creep up to 220 and all of a sudden shoot up to 260. But after a few minutes it will return back to 210-220 range. It obviously can't be really overheating if i don't need to turn it off, or even stop to have it cool off and correct itself. Just started doing it recently, so if anyone could help i would appreciate it!

CCKen

It may be actually getting that hot, or the engine Coolant Temperature Sensor is out of calibration. The PCM will turn on the radiator electric fan when the coolant temp gets to around 218*F +. It looks like your electric fan is kicking on and cooling down the coolant enough to return the temp to a lower reading...which is a good thing.

Next time your situation arises, open the hood and see if the electric fan is operating (engine running).

When is the last time you did a coolant change/flush, or changed your water pump?

Edit: Or changed your thermostat?

magpulcherokee44

I have done the fluids they're okay. I really don't think an electric fan is gonna cool it from 260 to 220 at the snap of a finger though, that seems highly unlikely. I really can't imagine any engine on this earth overheating, then cooling that instantly, the materials that make an engine block hold heat longer than that. So i still think its electrical. My water pump has never been replaced either so that might be going, possibly why it gets a crazy fluctuation in temp, the pressure might not be staying consistent. It could just be the temp sensor. I've just been spending too much money lately on this piece of ****, and more time under it than in it lol. I know thats the way jeeps go, but i have never had a vehicle be so temperamental for 6 months straight. Fix one thing, something else breaks. Anyone want a jeep?

djb383

Not a whole lot of parts to the cooling system of any vehicle, but if u replace/chase problems 1 part at a time, u eventually get there, just takes a while. Eventually the guess list gets short. Is there a 14 year old vehicle out there that doesn't require frequent TLC in order to remain a reliable DD? To me draining/re-filling coolant is slow and a hassle. Only way to do it once is to replace several parts at once. Who knows, when one starts the maintenance process, maybe a bad electrical connection/ground will just jump out at ya.

OnTheOffRoad

Check your electrical grounds could be the a little flaky and causing the gauges to not ready correctly, or the temp sender.
Backup reading of temperature when the gauge reads high would be good, handheld IR gun if you have or can get one.

My 89 does the exact same thing with huge quick temp changes, but not always. Yes it does run hot but has never 'over heated' in a classic sense; full meltdown, steam expolsion, power loss or head gasket snafu.
My guess (guess) is either the electrical conditions are changing causing the gauge to swing, or the thermostat is sticky causing the temp to rise, then it opens allowing a rush of cooler water into the 'system'. Scenario 2 would be bad, thermal stress on the block and head not a good thing.

magpulcherokee44

I appreciate all that but i don't have any more time/money for guessing. I just spent $3000 in the past 6 months, i would like to not add anymore to that tab unless its a sure thing. Water pumps aren't cheap, and neither are sensors.

Bbasso

if you don't want to guess or throw money out the window then invest in an affordable water temp guage and mount it OR the other option is pick up a scanguage which works in any 1996+ vehicle that is OBD2

djb383

I understand money is tight but a DD requires maintenance/TLC or else u r walking. The entire cooling system of the XJ can be replaced for <$250, including the radiator.......and 3-4 hrs in the driveway gits 'er done. I don't know of a cooling system out there that can be replaced for less money/in less time than the XJ......unless we're talking a air cooled motor.

magpulcherokee44

Lol that is true, then again i have a car too so i won't be walking if this jeep messes up. If you can find me the components for under $250 you are awesome. I looked on a site, they charge 80 for water pump, 200 for radiator, already over 250 for a couple parts. If you can repost the website you can get all that for under 250 i would appreciate it

CCKen

An Engine Coolant Temperature sensor is $20 at Advance Auto Parts for your Heep.

If it doesn't break your back, or bank, try one. But first make sure the pin sockets in the ECT sensor connector are clean and free from corrosion.

If your gauge is reading that high I'll bet your electric fan is running, regardless of if you think it is not lowering the coolant temp.

The same signals from the ECT sensor to the PCM that provides temp readout through the CCD Data Bus, turns the electric fan on and off. If you see over 220*F on the temp gauge so does the PCM.

magpulcherokee44

Never said the fan wasn't running, just saying its hard to lower 40 when something is at 260 thats all. i'll try that out it might be all it is

djb383

Have u looked at O'Reilly, Autozone, Advance, NAPA, Carquest, Pep Boys, etc.? Should be able to get the rad +/-$100, both the water pump and fan clutch for +/-$80 total, t-sat less than $10, rad hoses +/-$20, coolant/antifreeze +/-$20.....nuff money left over for pizza and beer. Maybe Santa will bring u a ScanGauge......we don't leave home without it.

Bbasso

I redid my entire cooling system with nearly all autozone parts, one from the Jeep dealer and the new radiator from the previous owner.
I did all of it with my own labor for less then $200.

It can be done. BUT BEFORE you do, get a proper temp guage.

djb383

If one shops really savy, I'd think <$400 would buy a total new XJ cooling system AND a ScanGauge. However, it would take an extra 30 seconds to install the ScanGauge.

magpulcherokee44

Ended up being a bad water pump, which i picked up for $30! The impeller was paper thin and barely had two fins left on it! The fact it was creating any pressure and didn't start overheating until now is truly amazing! Got a new coolant temp sensor, thermostat, radiator cap and flushed the system out. Everything runs beautifully now no overheating anymore. My electric fan actually never was working, unlike what some people had thought. But for now it will do, it isn't getting more than 40 degrees out during the day so the system never really exceeds 210, even in 4 Lo wheeling slowly with no airflow. Thanks guys for all your help!