i have owned a 2005 XJR for weeks now without a similar issue,, the coolant temprature slightly got higher than normal and needle reached the third quarter while stuck in traffic,, didn't reach red zone,, and it got bacj to dead center once car in motion,,

coolant level is correct and no warning lights,,

any ideas?

 

Lazy thermostat? Mechanics recommend replacing thermostats periodically.

 

any other ford car uses the same thermostat?
just in case i couldn't find a jaguar part,,

 

I don't know about Jaguars, but a lot of cars have thermostats that "misread" the temperature believe it or not. Engines always warm up in stop-and-go traffic but drivers freak out if they see their temperature gauges going up so they display the temperature in a non-linear fashion to avoid the "freak-out" factor. At least that's what someone told me.

It makes sense. My old BMW reads the "actual" temperature and it is constantly moving left to right depending on driving conditions. It never gets in the red, thankfully, but if it does I know it's for real!

 

Let the car sit there and idle. Does the fan come on???

Thermostats don't really open and close often when an engine is running.

The point of a thermostat is to allow the engine to get to normal operating temperature for proper fuel efficiency quickly, by restricting the flow of coolant, until the engine warms up. Once the engine is warmed up, it never really cools off below the threshold of a 180 or 160 degree thermostat. As we have all seen in fact without cooling, engines overheat.

So... what you are describing to me doesn't sound like a thermostat.

Thermostats fail in one of two ways. First they get stuck closed. No matter what you do, or where you are the car overheats... quickly. Coolant doesn't flow. Second option. Stuck open. The car never gets to operating temp. You don't really have any heat through the hvac system etc.

What you are decribing sounds much more like a fan problem. The fan is designed to kick on when the car is in slow or stangnat traffic, so it forces air over the radiator to dissipate heat. If it fails you get exactly what you saw. Once the car is in motion, there is sufficient airflow through the radiator, so the car cools back down.

Don't forget the Jaguar's gauge isn't really a "temp" gauge. It's more of an idiot gauge. Dead center is any temp that is deemed acceptable for operation. Not just a fixed number - say 200 or 210 degrees. The needle only moves when it's cold, or very hot.

Take care,

George

 

thank you George for the great info,, my problem now takes another direction,, let me explain it with more details,,

i left the car parked where the problem first happened,, i paid her a visit last night and ran the engine to observe,, coolant level was right,, both fan speeds kicked right,, the upper coolant hose got hot when the engine warmed up,, i guess that tells the thermostat got open for coolant flow back to radiator,, the car idles great without an issue,,

the issue appeared when i reved the engine up (car stand still) up to 3k rpm,, the temp needle jumped rapidly high,, shut down the engine but kept the key in ignition to monitor temp,, the needle shortly and rapidly jumped back to normal,,

please,, help,,

 

Bleed the coolant. That car has an air pocket in it blocking coolant flow...

There's plenty on here about bleeding. Remember heat on high while ur doing this.

Take care,

George

 

can you please tell how to do it,, a link will also be useful,,

 

where are bleeding screw located in an 05 XJR?

 

On the coolant expansion tank.

It looks like a little Phillips head plug on the top part in the black plastic part.


Be very gentle the plastic is brittle.

Take care,

George

 

you were absolutely right George,,
system bleeded and its fine now,,

thanks,,