Temp. sender, gauge or thermostat?

[ehall]

On a '96? I thought the last year for that was '91. 1991 was a transition year ... the first year with the HO motor, but still had 2 temp senders.

Yes I'm sure. There was a dedicated sender still there up into 96. They didn't formally consolidate temperature sender into the sensor until 97 gauge cluster swap over with bus. Some 96 may have it but they would be exception.

 

[gba88]

Ok, I found the sensor (sender?) in question. It was definitely right on the back of the head next to the main ground in the same location. It was also covered in dirt/grease so it's no wonder I missed it on a quick visual scan

Anyway, so I pulled the wire (single purple) and did the test ehall mentioned. Disconnected it's pegged left, connected to a ground, it's pegged right. I guess now it's time to find a replacement. Looks like a pretty tight working area, and also looks like it could snap off if you looked at it the wrong way! I don't know if mine was broke or not, but it didn't appear to have any kind of hook or clip that held the connector captive to the sender...just a nub on the sender that a slot on the connector slid down over and sort of snapped on to.

 

[montanaman]

Ok ... glad you found it ... sorry for my mistake. It is normal for the rear sender to have a stud sticking up, and the wire kind of slides down that with a grip.

 

[gba88]

Ok ... glad you found it ... sorry for my mistake. It is normal for the rear sender to have a stud sticking up, and the wire kind of slides down that with a grip.

No problem! I'm just glad I found it because I would have bought the entirely wrong sensor if I went with what I originally thought. I found a LOT of wrong information out there regarding the 95-97 years, so thanks a lot to ehall for verifying

 

[Tim_MN]

The temperature gauge can in fact jump form 210* to the red zone. If your cooling system is weak, your fan clutch is weak, your water pump fins are worn out, or your radiator cap is weak, the cooling system can overheat slightly and a steam pocket will form. The steam either stalls the flow of coolant, or flow through the system and when it hits the temp sensor you see it jump.


Service your cooling system as needed:

-Inspect the radiator for mud/bugs/grass clogging the outside and mineral deposits clogging the inside. Clean or replace as needed.
-Replace the thermostat with a STANT or Robertshaw 195* thermostat. Cheap thermostats are cheap for a reason.
-Replace the radiator cap if your Jeep has one. An old worn out cap will allow boil overs and/or allow the coolant flash over into to steam. You will see the coolant temps suddenly jump from 210* to the Red Zone and back to 210* if your radiator cap is weak.
-Inspect/test or replace the mechanical fan clutch. A worn fan clutch will allow temperature creep at stoplights, in heavy traffic, and on the 4x4 trails. A fan clutch that “looks” OK is not the same as working OK.
-Inspect the electric cooling fan and the fan relay. Apply 12 volts and make sure the fan runs. Exchange the cooling fan relay with one of the others similar relays. Confirm that the e-fan starts when engine temps reach 215-218*. Repair or replace the fan or relay as needed.
-Inspect/test or replace the coolant temperature sensor that activates the e-fan.
-Replace the water pump. The pumping fins can deteriorate over time and the pump will not flow enough coolant to keep the temps under control.


.

 

[gba88]

The temperature gauge can in fact jump form 210* to the red zone. If your cooling system is weak, your fan clutch is weak, your water pump fins are worn out, or your radiator cap is weak, the cooling system can overheat slightly and a steam pocket will form. The steam either stalls the flow of coolant, or flow through the system and when it hits the temp sensor you see it jump.


Service your cooling system as needed:

-Inspect the radiator for mud/bugs/grass clogging the outside and mineral deposits clogging the inside. Clean or replace as needed.
-Replace the thermostat with a STANT or Robertshaw 195* thermostat. Cheap thermostats are cheap for a reason.
-Replace the radiator cap if your Jeep has one. An old worn out cap will allow boil overs and/or allow the coolant flash over into to steam. You will see the coolant temps suddenly jump from 210* to the Red Zone and back to 210* if your radiator cap is weak.
-Inspect/test or replace the mechanical fan clutch. A worn fan clutch will allow temperature creep at stoplights, in heavy traffic, and on the 4x4 trails. A fan clutch that “looks” OK is not the same as working OK.
-Inspect the electric cooling fan and the fan relay. Apply 12 volts and make sure the fan runs. Exchange the cooling fan relay with one of the others similar relays. Confirm that the e-fan starts when engine temps reach 215-218*. Repair or replace the fan or relay as needed.
-Inspect/test or replace the coolant temperature sensor that activates the e-fan.
-Replace the water pump. The pumping fins can deteriorate over time and the pump will not flow enough coolant to keep the temps under control.


.

Dang, and I thought I was gonna get away with just replacing the sensor Just kidding, Thanks for the great info and explanation on how the gauge jump may be explained! Not sure what I'll do now... maybe replace the sensor and the cap since that will be the quickest easiest fix to see if it helps in the short run, and won't cost much. The radiator is most likely due for a flush and at that time, I'd do the thermostat, too. The biggest thing for me is finding the TIME do do this stuff. I was thinking of pulling the hose and flushing the radiator anyway, so now I have all the more reason. I'll post back to this thread once I've made any progress or discoveries Thanks again for all the help!

PS how many miles were on that waterpump!? I can't believe that picture is even real!

 

[gba88]

Please let us know if that fixed it i'm having sort of the same problem

Hey guys,
just a followup. I did 2 things, first I bought the stant radiator cap from a napa store, and then I bought a new sender. I cheaped out and went against logic knowing full well that everyone reported the bad experience with sensors from advance, autozone, etc. Anyway, yeah, it was reading about 20-30 degrees too high.

Interesting note: when i went to take out the old sender, the stem kind of "crumbled" off and the insulating material was the consistency of compacted cardboard...it was just kind of crumbling apart! So after all that I ordered the exact sender from a local dealer for about 20.45. Although I haven't driven in 98 degree weather again, I have had it heated way up and sitting in traffic it's not jumping like it used to. I guess time will tell, but it appears to be ok at the moment.

I wish I could figure out the increments on the gauge though! It starts at 100...then 210 in the middle and 260 at the end. Anyone know what numbers the slashes in between (right and left of middle) are? The increments are surely not equal because if left is 100 then 210 is the middle, the rightmost slash would be 320, not 260! Also, what's the best place to check with an infrared thermometer? I was checking the head back by the sensor and also the theromstat housing. Pretty tough to figure it all out though with the gauge being labeled the way it is.