I have 2005 Jaguar x-type 3.0L. The engine run hot when I'm in traffic. As long as I'm driving it is fine the engine gauge never passes the middle mark. What could be the problem and the estimated cost of repair.

It mite not be running hot at all , I replaced a few stepper motors for the temp. gauge inside the instrument cluster . GM products of your year ,have known instrument cluster gauge problems . Best thing is to hook up to a factory scan tool or another type of professional grade scan tool to see what the engine computer is seeing from coolant temp.sensor Do your cooling fans come on ? They should at about 221 degrees . Or you came go to harbor freight an by a temp. inferred gun. point it at the upper radiator hose near the thermostat , an see what the actual temp. is . How to repair GM Instrument Cluster Speedometer Gauge Stepper

the first thing to check is to feel if the radiator is hot, if the radiator feels hot and the engine is also hot the coolant is circulating ok then the problem is more than likely electrical, the temp gauge gets its signal from the engine control module the coolant temp sensor sends coolant temp signal to engine control module for engine managment purposes then passes it to instument pack/gauge, if the sensor was at fault you would have engine running problems also,with poss fault codes logged, if the engine and rad are cold/only warm after the engine has been run for 15 mins or so it sounds like the thermostat is stuck open but you have changed that. i have had faulty new ones in the past and have had to test them in a pan of boiling water, hope this is some help to you.

any engine check light on ?
could be the idle control sensor

For car running hot and overheating issues, I suggest to you go through this help links. Click this link below and go through the troubleshooting procedure to take care of the problems: ----Car runs hot? http://howtobyme.blogspot.com/2011/11/car-runs-hot-in-traffic.html
-----------All types of car overheating problems and troubleshooting?

http://technoanswers.blogspot.com/2011/11/all-types-of-car-overheating-problems.html
Car freeze overnight and started overheating while driving?http://technoanswers.blogspot.com/2012/01/car-freeze-overnight-and-started.html-----------Engine Overheats and heater blowing cold?

http://howtobyme.blogspot.com/2011/11/engine-overheats-and-heater-blowing.html

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Car overheats and Air blows hot at idle?
http://howtobyme.blogspot.com/2011/11/car-overheats-and-air-blows-hot-at-idle.html
--------overheating? http://schematicsdiagram.blogspot.com/2011/12/buick-century-overheating.html
----------Car engine Overheats and transmission starts slipping?http://schematicsdiagram.blogspot.com/2011/12/car-engine-overheats-and-transmission.html
----------This details will help.Thanks.

For car running hot and overheating issues, I suggest to you go through this help links. Click this link below and go through the troubleshooting procedure to take care of the problems: ----Car runs hot? http://howtobyme.blogspot.com/2011/11/car-runs-hot-in-traffic.html
-----------All types of car overheating problems and troubleshooting?

http://technoanswers.blogspot.com/2011/11/all-types-of-car-overheating-problems.html
Car freeze overnight and started overheating while driving?http://technoanswers.blogspot.com/2012/01/car-freeze-overnight-and-started.html-----------Engine Overheats and heater blowing cold?

http://howtobyme.blogspot.com/2011/11/engine-overheats-and-heater-blowing.html

---------------------------
Car overheats and Air blows hot at idle?
http://howtobyme.blogspot.com/2011/11/car-overheats-and-air-blows-hot-at-idle.html
--------overheating? http://schematicsdiagram.blogspot.com/2011/12/buick-century-overheating.html
----------Car engine Overheats and transmission starts slipping?http://schematicsdiagram.blogspot.com/2011/12/car-engine-overheats-and-transmission.html
----------This details will help.Thanks.

For car running hot and overheating issues, I suggest to you go through this help links. Click this link below and go through the troubleshooting procedure to take care of the problems: ----Car runs hot? http://howtobyme.blogspot.com/2011/11/car-runs-hot-in-traffic.html
-----------All types of car overheating problems and troubleshooting?

http://technoanswers.blogspot.com/2011/11/all-types-of-car-overheating-problems.html
Car freeze overnight and started overheating while driving?http://technoanswers.blogspot.com/2012/01/car-freeze-overnight-and-started.html-----------Engine Overheats and heater blowing cold?

http://howtobyme.blogspot.com/2011/11/engine-overheats-and-heater-blowing.html

---------------------------

Car overheats and Air blows hot at idle?
http://howtobyme.blogspot.com/2011/11/car-overheats-and-air-blows-hot-at-idle.html
--------overheating? http://schematicsdiagram.blogspot.com/2011/12/buick-century-overheating.html
----------Car engine Overheats and transmission starts slipping?http://schematicsdiagram.blogspot.com/2011/12/car-engine-overheats-and-transmission.html
----------This details will help.Thanks.

Check the water pump and also check the radiator for blockage, make sure that fluid pours out the bottom of the radiator with the lower hose disconnected

Thermostat got stuck. Replace it. I am surprised a shop couldn't tell that.

the heater control valve is often the cause of this. there are 3 metal lines running down the right fender, if 2 are hot and 1 is not with AC on max the valve has most likely gone bad,

Prob a headgasket leak, I would have a shop preform a leak down test. The test only cost about 99 bucks or so at a indy shop.