Theres more than a half way decent chance the sensor was bad out of the box.

 

That's true, and I wouldn't be surprised, but I've also been told that the gauge light should come on during start up whether theres a good/bad, plugged in/unplugged sensor. It's only come on that one time and I don't think it was overheating but now I'm paranoid.

 

So I just checked my '96 with the gauge cluster and also checked the owner's manual. Only 3 lights in my cluster come on with the key in the on position. Seat belt,check engine,and generator warning. Manual doesn't say that the coolant warning light in your cluster comes on when starting the engine.

 

Thank you. Do you have the idiot lights or full gauges?

 

I have the full gauge cluster. It had the idiot light cluster when I first bought it but my first mod to the vehicle was to replace it. The coolant warning light in the original cluster did come on one time when ascending a 5mi 9% grade road but replacing the fan clutch fixed it.

 

Well, I lost my records of my part-out in a hard drive stupidity. However, my son thinks we still have it. According to my part out thread, I still have it. It's from a 94, but I believe they are the same. (Someone chime in if you know otherwise.) A 97 and later would not work for you.

I'll start digging tomorrow and see if I can find it, and post a pic or two.

 

I would've been interested in all the badges off your old jeep but I see you've gotten rid of it, oh well

 

Any luck with that cluster, BlueRidgeMark?

 

Yeah, sorry, I lost this thread. I checked, and it's gone. My son remembers shipping it to some guy in Alaska. Sorry!

 

The scan tool is reporting the official engine temperature that the PCM uses. The sensor is the Coolant Temperature Sensor.
In a related thread I explore why everyone seems to think it's ok to exceed 195F in the xj, when that is what the correct T stat is, 195.
I do believe the cooling system is supposed to maintain 195 if that's what the T stat is.

 

It's all good, I appreciate you looking.

 

That's not the designed running temperature. That's just the temp at which the T-stat begins to open.

 

This is a topic of some debate apparently but it always seemed crystal clear to me. My position is that the thermostat is the component of the system that controls the running temp, all other things working right. If the thermostat does not regulate the coolant temp, then what pray tell does? The weather? Whether you run the AC or not? A long steep graded hill? What makes you think it BEGINS to open at 195 and not RUN ant 195? My zj sits at 194-195. This is what the fsm says.
THERMOSTAT
A pellet type thermostat controls the operating temperature of the engine by controlling the amount of coolant flow to the radiator.

Apparently, however, especially it seems in the case of the xj, the thermostat is often not able to control the operating temperature, and they added the electric fan.

 

Automobiles get rid of heat in three basic ways: the coolant system, the heater core, and the exhaust. Some have oil coolers also but I'm only dealing with the basics here. Have you checked the cat converter and the muffler for any restrictions or blockage? Is there a leak in the exhaust manifold or piping that is redirecting exhaust gas back onto the engine? If the radiator is not new have you had it cleaned by a shop to insure there is absolutely no blockage? Have you inspected the water pump to insure all the internal splines are still there? Is the fan running at full speed under the hottest conditions? Are the spark plugs the correct ones for that engine? Is the air intake system providing enough combustion air to the engine?
I'm just throwing this all out there because sometimes we have to go back and start at the basics.

 

Yes, because too many people do not have a basic understanding of thermodynamics and the design of vehicular cooling systems. They cobble together ideas based on bits of information and ideas gleaned from various sources, some of which are incorrect. The Internet has enabled the sharing of errors on a mass scale never seen before.


Well, your position is incorrect.


There are a host of factors, of which the thermostat is only one. It is a complex dance of heat loss and gain.


A basic understanding of the correct operation of a vehicle cooling system, as learned in school, lo, these many decades ago. This is not a debatable subject, in the sense that nobody really knows and it's up to a personal interpretation. This is basic stuff. YOu can probably find a good textbook on the subject if you like.

Oh, and you can test it yourself, which I have done many times.


Fine. XJs sit at 210. With a 195 T-stat.

It controls the flow of coolant, yes, and thus affects the engine temperature, but that does not mean that "thermostat temperature rating" = "engine running temperature". It's not nearly that simple.


Thank you. That one sentence demonstrates that you do not understand how a vehicle cooling system works. It's completely wrong.