Well my jeep wont stay cool.
CF Veteran
Joined: Feb 2016
Posts: 3,683
Likes: 8
From: Northern New Mexico
Year: 1999
Model: Cherokee
Engine: 4.0
Ok a little more testing before i returned the tools. Left the pressure tester on the cold engine and it held 15-16 psi for over an hour. Next I ran the engine with the pressure tester connected. Pressure on tester got up to 12 psi but my gauge read 240 degrees and i felt like my hoses were way too tight so i shut it off and removed the tool. Never found any leaks with pressure test.
So after the test i fired it back up with the rad cap off in hopes of maybe some more air burping free. At this point it has been idling for 30+ mins. Hooked up my obd2 scanner for live data and shows 210 degree coolant gauge showing 240. replaced cap. Decided to drive it some, about 4-5 miles and gauge got up to around 240 again. Oddly my obd scanner had dropped to 150 degrees.
Decided to bring out the infared reader and this is what i recorded at idle after the above.
Gauge
OBD live data
Infared temp at sensor in thermo housing
Infared temp at thermo housing
Infared temp at Rad cap
Infared temp at radiator core by lower hose
All these pics are take back to back while idling
I think its odd my obd scanner jumped from 210 to 160 on a 5 mile drive, then again this was at night not during the day when its 95+ degrees outside. But it hasn't registered a temp that low since ive started all this. All in all my readings seem all over. The aux fan comes on with ac but hasnt gotten hot enough to turn on by itself but once during a day test drive and then my obd scanner was reading 223 degrees. Im stumped.
So after the test i fired it back up with the rad cap off in hopes of maybe some more air burping free. At this point it has been idling for 30+ mins. Hooked up my obd2 scanner for live data and shows 210 degree coolant gauge showing 240. replaced cap. Decided to drive it some, about 4-5 miles and gauge got up to around 240 again. Oddly my obd scanner had dropped to 150 degrees.
Decided to bring out the infared reader and this is what i recorded at idle after the above.
Gauge
OBD live data
Infared temp at sensor in thermo housing
Infared temp at thermo housing
Infared temp at Rad cap
Infared temp at radiator core by lower hose
All these pics are take back to back while idling
I think its odd my obd scanner jumped from 210 to 160 on a 5 mile drive, then again this was at night not during the day when its 95+ degrees outside. But it hasn't registered a temp that low since ive started all this. All in all my readings seem all over. The aux fan comes on with ac but hasnt gotten hot enough to turn on by itself but once during a day test drive and then my obd scanner was reading 223 degrees. Im stumped.
Thread Starter
Junior Member
Joined: Jul 2016
Posts: 36
Likes: 0
From: Glennville,GA
Model: Cherokee
Ive changed the Sensor in the head with a new one from autozone. I have not changed the sensor in the thermostat housing. I made sure to get the one for a gauge and not a light. The scanner is OTC brand, hasnt ever given me false info before and stays pretty steady with readings hasnt jumped around much.
Newbie
Joined: Aug 2016
Posts: 3
Likes: 0
Model: Cherokee
Are you 100% sure your water pump is good? My '95 was running about the exact same temperature and it ended up being the water pump. Also, have you visually inspected to see if your AUX fan comes on?
If the guy who owned it before claimed to replace the water pump but your not sure that is the first place I would look.
If the guy who owned it before claimed to replace the water pump but your not sure that is the first place I would look.
Thread Starter
Junior Member
Joined: Jul 2016
Posts: 36
Likes: 0
From: Glennville,GA
Model: Cherokee
I have replaced the water pump with a new parts store unit a few days ago with not much change in cooling. Aux fan will come on with ac and defrost. doesn't seem to get hot enough for the pcm to turn it on unless i really push it.
Thread Starter
Junior Member
Joined: Jul 2016
Posts: 36
Likes: 0
From: Glennville,GA
Model: Cherokee
Did some more testing. Decided to drive it. Drove about 20 miles and it stayed at 240 with the ac on wouldn't really creep up long as i dont sit for too long. Turned off the ac and it would hover right at the red. Got it home and hooked up the obd scanner. Gauge right on the edge of red but my scanner says coolant temp 217 about this time the aux fan kicked on. Never acted very hot or boiled over but the resevoir was filling to the top so i shut it down.
Thread Starter
Junior Member
Joined: Jul 2016
Posts: 36
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From: Glennville,GA
Model: Cherokee
Next morning the overflow is at the add line.
Just ran it again this morning up till 240 degrees. The upper and lower hoses get hot but not like they should. They honestly feel like they are full of air and not really circulating anything. Now the heater hoses get really hot and i can feel fluid going through them. If its air i cant find where its coming from unless its a warped head and in that case the pressure tests and no water in oil isnt showing that.
Just ran it again this morning up till 240 degrees. The upper and lower hoses get hot but not like they should. They honestly feel like they are full of air and not really circulating anything. Now the heater hoses get really hot and i can feel fluid going through them. If its air i cant find where its coming from unless its a warped head and in that case the pressure tests and no water in oil isnt showing that.
Last edited by 96jeeper; Aug 12, 2016 at 10:14 AM.
Senior Member
Joined: Mar 2014
Posts: 952
Likes: 55
From: Eastern Long Island, NY
Year: 1996
Model: Cherokee
Engine: I6 Cyl / 4L
Don't really understand everything that is going on, but it may be your temp gauge in the instrument cluster is acting wacky.
I would keep testing the gauge readings with different interval readings from the infrared temp gun pointing at the thermostat housing at the front of the engine. Make sure you use a good temp gun because I have had some give me bad readings, especially with the heat of the engine bay which can mess with them.
But if the temp gun matches closely to the temperature of the OBD scanner, then I would question the gauge in the instrument cluster.
I would keep testing the gauge readings with different interval readings from the infrared temp gun pointing at the thermostat housing at the front of the engine. Make sure you use a good temp gun because I have had some give me bad readings, especially with the heat of the engine bay which can mess with them.
But if the temp gun matches closely to the temperature of the OBD scanner, then I would question the gauge in the instrument cluster.
Thread Starter
Junior Member
Joined: Jul 2016
Posts: 36
Likes: 0
From: Glennville,GA
Model: Cherokee
My jeep is overheating. Getting up to 250+ degrees in any condition. Idle,driving etc. Have changed every cooling part except the head/block. Symptoms still same as day 1. Checking the temp with the gauge,infared gun, and obd scanner I get 3 diff numbers none close to each other. Doesn't seem to be just a gauge issue as it will cut on my aux fan by itself and the coolant will overflow out of the reservoir if i allow it to get that hot. Running it with ac or heat on seem to help hold it around 230 degrees but will still climb if i sit to long or push it hard.
Senior Member
Joined: Mar 2014
Posts: 952
Likes: 55
From: Eastern Long Island, NY
Year: 1996
Model: Cherokee
Engine: I6 Cyl / 4L
I don't understand why you are getting different temp readings at the same time. If you take a reading at the same time with the temp gun, look at the gauge, and the OBD scanner, they should be close to each other. If not, then you are doing something wrong, or there is something wrong with the diagnostic equipment. You need to figure that out first before moving forward. Borrow different tools then, take it to a garage maybe. Could be there is nothing wrong with the Jeep but the readings.
Thread Starter
Junior Member
Joined: Jul 2016
Posts: 36
Likes: 0
From: Glennville,GA
Model: Cherokee
Ok after your post i decided to test again. On a cold engine i ran it up to temp idling. Gauge got to 240. Scan tool says coolant temp 205. Got my infared and put it about 2-3" from t-stat housing and it was 190-195. I may not have been close enough before.
No overheating symptoms during this test but noticed if i squeeze the upper hose i get some coolant drips from the new radiator cap so i may need to try another one.
No overheating symptoms during this test but noticed if i squeeze the upper hose i get some coolant drips from the new radiator cap so i may need to try another one.
Senior Member
Joined: Mar 2014
Posts: 952
Likes: 55
From: Eastern Long Island, NY
Year: 1996
Model: Cherokee
Engine: I6 Cyl / 4L
You really need to keep testing it with the temp gun pointed at the thermostat housing where the coolant sensor screws into. That will give you a closer reading to what the engine temp is.
Bring it to idle and test. If the temp holds steady at idle (for like 15-20 minutes), take it for a short local drive, stop, leave it idling, and test again. If the temp is steady and within normal operating temp, then you know it is either the sensor, gauge, sensor wiring or PCM (but I doubt PCM since the OBD reading matches the temp gun reading more closely) that is giving you the faulty reading.
Bring it to idle and test. If the temp holds steady at idle (for like 15-20 minutes), take it for a short local drive, stop, leave it idling, and test again. If the temp is steady and within normal operating temp, then you know it is either the sensor, gauge, sensor wiring or PCM (but I doubt PCM since the OBD reading matches the temp gun reading more closely) that is giving you the faulty reading.
CF Veteran
Joined: Dec 2015
Posts: 2,139
Likes: 93
From: Syracuse, NY
Year: 1996
Model: Cherokee (XJ)
Engine: 4.0L
I would recommend getting a FSM for the 96 and reading up on the "Coolant Temperature Gauge" (pg 8E-4).
Here is a nice quote to get the point across:
"The PCM uses input from the coolant temperature sensor AND internal programming to decide what engine cooling temperature message is required. The PCM then sends the proper message to the instrument cluster on the CCD data bus".
Thread Starter
Junior Member
Joined: Jul 2016
Posts: 36
Likes: 0
From: Glennville,GA
Model: Cherokee
So we may be onto a bad gauge/sensor. Hooked up the obd scanner and set live data for coolant temp. Started a trip to the store watched it climb to 160-170 degrees on the scanner even though the gauge inside said 215. By the time i reach the store the gauge says 240 but the scanner says 205 and holding. I then proceeded home. Gauge stayed at 240 and scanner at 205. Hop out pop the hood put the infared on the tstat housing it registers 190-200. Left it running for 15 mins and the numbers remained the same. no leaks or coolant backing into the bottle. Now given this was at night so the outside temp is upper 80s. Will test again tomorrow when its upper 90s.
Could i be looking at a bad temp sensor from autozone or a possible bad gauge?
Could i be looking at a bad temp sensor from autozone or a possible bad gauge?
CF Veteran
Joined: Aug 2009
Posts: 5,676
Likes: 301
From: WV
Year: '96
Model: Cherokee
Might want to buy a MOPAR sensor. I guess you could try one from the JY. I bought a factory one after doing a instrument panel swap and had a temp gauge problem when I used an aftermarket sensor.
Thread Starter
Junior Member
Joined: Jul 2016
Posts: 36
Likes: 0
From: Glennville,GA
Model: Cherokee
Yea thats probably my issue. im thinking of just doing away with the factory gauge and running an aftermarket gauge with sensor in the head for a more accurate gauge.
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