• NAXJA is having its 18th annual March Membership Drive!!!
    Everyone who joins or renews during March will be entered into a drawing!
    More Information - Join/Renew
  • Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.

Temp Gauge acting screwy

RedJeepXJ

NAXJA Forum User
Location
Portsmouth, VA
Two days ago my Check gauges light came on, and I noticed the temp gauge was at 260, I started slowing down to pull over and it jumped back to normal operating temp. The same thing happened today, the check gauges light came on and the temp gauge jumped to 260, about 10 seconds later it dropped back to normal operating temp. Any idea what might be wrong.
 
If your senders are in good shape, make sure that you have enough coolant. When the senders get uncovered by water, and are in air/vapor, the temp will apparently skyrocket.

I do suspect that you're low on coolant, and you've got a bubble in the head.
 
I checked the coolant in the radiator and it was full to the cap, the overflow was also between the add and full mark. What's the best way to check for an air bubble in the head?
 
The problem is that the passage in the head is above the radiator and that's where the bubble naturally migrates to.

Think about "burping" your cooling system (yes, this gets discussed on a pretty regular basis.) There are several methods.

One is to jack up the rear end so that the engine now sits nose down, rather than nose-high. Remove the temp sender/sensor from the rear of the head (single wire hookup, driver's side by the valve cover) and fill there.

I played games with the head on my XJ last fall, replaced a head gasket the day before I left for Moab. I watched the temp gauge bounce around driving across IL, and half way across IA before the bubble in the head finally got pushed through the thermostat and into the radiator where it could escape through the cap into the overflow. Yes, it took several hours of hard running.
 
The temperature sensor on my Jeep is located on the thermostat housing, is the procedure for burping the same as if it was on the back of the motor?
 
RedJeepXJ said:
The temperature sensor on my Jeep is located on the thermostat housing...

I could be wrong, but I think that's just the sensor for the PCM. The sending unit for teh guage is still at the rear of the head, drivers side. Looks like a bolt with one wire stuck to the top of it.

Sequoia
 
I just went out and checked and didn't see any wires coming from the back driver or passenger side of the head, I know my old Jeep had one back there, but I don't see one on this one.
 
The sensor that WAS screwed into the back part of the head on the passenger side was discontinued several years back. On the 97+ 4.0L there is ONLY one sensor and it screws into the t-stat housing. This does double duty as a sensor for the PCM to control the electric cooling fan and send a signal to the temperature gauge.
I think I would check loose wires, grounded wires from the sensor. When was the last time the t-stat was serviced ??? There is a possibility that the t-stat my have a problem (ie. not opening or being obstructed).
 
Back
Top