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98 ZJ 5.9 cooling system question

13K views 14 replies 7 participants last post by  LipschitzWrath 
#1 ·
OK so i have the display in my 98 zj 5.9 right in front of the shifter that pretty much tells you anything wrong with the jeep. Its flashing coolant sensor bad. Now when i look around under the hood i see at least 2 sensors. One in the upper hose and one in the lower hose. Im told that there are 2 more someplace? I haven't really searched for others. Just took a quick look. Temp gauge works so what sensor is bad? Any ideas? Thanks guys.
 
#2 ·
My 94 shows that sometimes.

I usually just pat the dash a little and tell it I love it, and it will go away for a few months. Honestly.

But then again my old Jeep is haunted. It had a radiator leak and I told it I was sorry and poured in some stop leak, and it never leaked again. The radio only works when I am the only one in the Jeep. If I have my wife or son, or friends in the Jeep it won't work. The light switch on the driver door sticks and I pat the door and it will go off. The rear wiper sticks and I talk to it and it will wipe. I have a Jeep like Christine.
 
#3 · (Edited)
lol yea you got some gremlins. the cooling system on the 5.9 is a bit different though. It seems that one of the sensors is for the gauge and one is for the electric fan. The 5.9 doesnt have a clutch fan only electric. Just curious what OTHER sensors are under there. The gauge works and the electric fan works. Whats causing this message?
 
#4 ·
This could possibly be a false alarm. The VIC (vehicle info center) could be bad. The wire that is connected to the sensor may need to be re-soldered to the circuit board. Its a common problem.
 
#7 · (Edited)
OK i checked for sensors. One in the upper hose, one in the lower hose, one in the manifold next to the water neck and one in the over flow bottle. Reason i dont think it's a wire is because it's not always on. Ill check the wire anyway just to be sure though. Where is this wire located? Right behind the display on the dash?

OK well after doing some homework i have learned a few things. Both sensors in the hoses are for the electric fan. One is for the low speed setting one is for the high speed setting. That makes be want to say the sensor in the intake manifold is for the gauge and the one in the tank for a fluid level sensor. Now like i said above, the gauge works as does the electric fan. I think its safe to say the sensor in the tank is causing the problem if it's not the broken wire. What do you guys think?
 
#12 ·
Yes it did, worked perfectly. The VIC is a little tricky to get apart if you rnot good with this stuff and you should use a soldering iron with a point tip. You will need to add solder. As soon as you heat the factory solder it pretty much just disapears. I think the problem is they just didnt use enough to begin with.
 
#14 ·
VIC= Vehicle Information Center. It's the display that is under the heater controls that displays the time and date and has the pic of the jeep on it.
 
#15 ·
The coolant sensor it is referring to is the one in the overflow bottle. It's a common problem with these Jeeps. Comes and goes, really not that big of a deal.

Now, to explain what the other sensors are for. The sensor near the thermostat housing is the sender for the gauge. The one in the upper hose activates "low" speed on the fan when it reaches a preset temperature. Similarly, the sensor in the lower hose activates the "high" speed on the fan when it reaches its preset temperature. Interestingly enough, the sensors are the exact same, and these turn on temperatures are the same. The lower hose should always be cooler than the upper hose though, which is how the system works.

Also, your electric fan will kick on anytime the A/C is engaged.
 
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