Ok so I have a problem....
First things first. I have a 99 cherokee with the 4.0 and auto tranny. Before I state the problem here is what I have done:
-Change the thermostat
-Back flush the system
-Replace the fan clutch
-New fan shroud (old one was broke)
Ok so heres my problem. If I drive for more than, oh, lets say 35 minutes or so on the highway at around 80 the jeep will over heat. Not just a climbing temperture overheat, It jumps from about 210-215 al the way to 250-260 in less than a second. Sometimes it goes back to operating temp. in a few seconds sometimes it doesnt go away untill I pull over and turn it off. Now this only happens when I am going down the highway(75+mph). This normally doesnt affect me cause I drive about 25 minutes to work (all highway), but I have noticed that once it happens, it is more likey to continue happening on the same trip. But if I shut off the car for five minutes I can drive another 15 to 30 minutes before it happens again. I drove from Nashville to Louisville and it did it about 6 or 7 times on the way up (during the heat of the day) but only did it once on the way back. But it is truly overheating, coming out of the overflow and all. I took the jeep to the stealership and they wanted to back-flush the system put in a new radiator and therostat. Bump that.
Ok I have 3 theories:
(1) My lower radiator hose is collapsing under the pressure of the water pump. Thus the reason speed (RPM=Pressure) and heat (Making the rubber Hoses softer) play an important part. Also, where the hose connects to the water pump feels really soft.I dont know if that would cause the super-sudden jump in tempature, but it would explain why its fine for a little while if I shut it off and then turn it back on.
First things first. I have a 99 cherokee with the 4.0 and auto tranny. Before I state the problem here is what I have done:
-Change the thermostat
-Back flush the system
-Replace the fan clutch
-New fan shroud (old one was broke)
Ok so heres my problem. If I drive for more than, oh, lets say 35 minutes or so on the highway at around 80 the jeep will over heat. Not just a climbing temperture overheat, It jumps from about 210-215 al the way to 250-260 in less than a second. Sometimes it goes back to operating temp. in a few seconds sometimes it doesnt go away untill I pull over and turn it off. Now this only happens when I am going down the highway(75+mph). This normally doesnt affect me cause I drive about 25 minutes to work (all highway), but I have noticed that once it happens, it is more likey to continue happening on the same trip. But if I shut off the car for five minutes I can drive another 15 to 30 minutes before it happens again. I drove from Nashville to Louisville and it did it about 6 or 7 times on the way up (during the heat of the day) but only did it once on the way back. But it is truly overheating, coming out of the overflow and all. I took the jeep to the stealership and they wanted to back-flush the system put in a new radiator and therostat. Bump that.
Ok I have 3 theories:
(1) My lower radiator hose is collapsing under the pressure of the water pump. Thus the reason speed (RPM=Pressure) and heat (Making the rubber Hoses softer) play an important part. Also, where the hose connects to the water pump feels really soft.I dont know if that would cause the super-sudden jump in tempature, but it would explain why its fine for a little while if I shut it off and then turn it back on.