Normally I would think nothing of it but after reading another thread I am now curious.

My 98 XJR always runs its cooling fan for a couple minutes after I shut it off. It is Texas and getting hot but the car will do it even if I just turn on the ignition ket then back off. This morning I noticed I left it outside overnight (by accident) so I just backed it in the garrage and the fan continued to run for apx 2 minutes. Not sure as I havent timed it.

The cooling system is properly filled with no air bubles. Engine does not over heat (verified with LASER temp gun). Outside air temp sensor works.
Since this is my first Jag I was wondering if thats just how the car is or do I have a sensor failing?

 

My 98 XK8 and 99 XJ8 both have their fans run for a minute or two after the car is turned off. It may be based on certain temperature as they do not stay running when its very cold outside. Just think of all of the heat created when the car is run, and then, suddenly turned off. I believe that having the fans on is part of the design.

 

The fans are controlled by two or more sensors, if the sensor(s) is reading the temperature is high enough, it will turn on the fans, regardless if the car is running or not. That is why that little note is there (should be) to "Keep Hands Away".

I never had a car fans come on just pulling it into the gargage, check the sensors with a ohms meter for the resistance, if it out of specs then it time for replacements.

For most owners, reading sensors is like reading Chinese. But once you start to understand it; it will be very useful in repairing your vehicle, specially when it comes to sensors.

Every sensor, relay, wire harness, etc... has a resistance value and it is out of spec, mostly it will be the cause of your problem or within the path.

 

To counteract the increase in engine coolant
temperature that occurs after the engine stops,
at ignition off:

• if the fans are already on, the ECM keeps
them on for 5 minutes, or until the ECT
decreases to a pre-determined value,
whichever occurs first

• if the fans are off, the ECM determines, from
ECT and intake air temperature inputs, if the
fans need to be switched on. If they do, it
switches them on for 5 minutes, or until the
ECT decreases to a pre-determined value,

whichever occurs first.

 

i live down in miami and run the air c all the time in the car...in the hottest of days my fans next to never come on after i turn the car off...the only time they have is when one of my little plastic hoses blew on me and i was losing coolant...you might want to pressure test your coolant system to see if you have a small leak...some leaks won't show up unless the system is under pressure or hot...you can rent a coolant test at advanced auto parts...

 

Thanks all for the input. I will be bringing it back to my shop on Friday and I can hook it up to my Matco scanner and map all the sensors and even manipulate them with the scanner to see if they are working correctly.

As for the cooling leak, the car does not CURRENTLY have one but is right on the verge. I was at a friends house tonight and hes the area Jag mechanic. He was in love with my XJR and since he sees them every day that made me feel better about my purchase. Anyway as we were staring at the engine talking about the fan (he don't think its an issue due to the heat but said it couldn't hurt to scan it) he pointed out the bypass hose that feeds the thermostat housing to the water pump inlet was very swollen. Upon touching it I could feel it was like mush. I do not wish to destroy the car or get stranded so I will have to wait for a new hose to show up. I can not get the hose locally so I ordered from Rock Auto with a rush request so I can enjoy the car this holiday weekend.
My new shocks, blower pulley and CAI have all arrived so I would like to play with my new toys.

 

So I bring her to my shop today to wait for parts and as I had a little spare time I put it on my 3rd bay rack to pull the rotors off and turn them in anticipation of the ceramic pads on the way. While I was in there I poked the swollen hose with my finger and it popped. LOL. Tried to get a parts store 90* 1 3/4" hose to work but its a compound bend and it just wont work to my liking. Unfortunately while removing the old hose I managed to snap the surge tank feed line at the thermostat housing. Yay me. Took forever to locate that hose only to discover whoever priced it must be into hard core pharmaceuticals because $200 is insane. Just made a whole new hose from 1/2" heater hose and barbed couplers. Its not as "sleek" as the tiny hard plastic line but it was $195 cheaper and will prolly last longer.


So thats my fun for today.


Oh yeah, forgot about the dang coolant. Took forever to figure out what was in there, supposed to be in there and whats in there now. I guess since the car is a pre 99 that it does not have the Dexcool based crap and it could have had yellow or green which is both compatible with each other. Makes me feel a little better because the surge tank coolant and neck coolant looked green in the car and almost golden when spilled on the bay floor. Wasn't looking forward to spending $16 a liter on the Jag coolant but since its green I can buy the G05 cheap stuff.

 

Also as a bonus my buddy gave me a cooling fan setup off an 01 XJR for free as a backup if mine ever fail.