Thermo check
 

In several threads I have seen reference to "checking the thermostat is opening correctly". Is there a method for doing this without taking it out of the car? Also, whilst preparing for test yesterday, I managed to break the bleed pipe that runs from the header tank to the thermostat housing. I was able to repair it with a small length of narrow gauge rubber hose but obviously lost an amount of coolant. I topped this up with clean water as I didn't have any orange antifreeze available.
Following the test ( which the car passed ) whilst driving to shopping centre, I noticed warm air coming from some vents, not a thing that normally happens as I have a heater problem, so on stopping I lifted the bonnet, (hood) to see if heater pump was running and found main rad fan running, and quite fast. I have not known this fan to be needed or seen it running in the 2 months since I bought the car, and wondered if the engine could be overheating.
Have recently changed the thermo housing for the metal type, and a new thermo was put in, but being new doesn't guarantee it 's working.
So all in all, what could have caused the rad fan to suddenly start running "out of the blue" when I don't believe it has previously? Unfortunately, the nice "centre only" jaguar temp gauge doesn't help one bit. Suggestions pls guys !!

Further to above, the coolant has been topped up with water twice recently, and one thread I read stated (or suggested) that weak antifreeze mix was a possible cause of overheating. I can't remember whose thread it was, but can this really be correct?

I'll be trialing one of WhiteXKR's digital "Realgauge" conversions shortly, I'd recommend fitting this as it'll remove all doubts.
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There's been a long running thread on how useless the factory temp one is, with engines having overheated before the display runs into the red. Being a 2000 car does it have the later upgraded water pump fitted?

The coolant mix should be a 50/50 mix - you can check this for free at a local motorfactors, they'll have a hygrometer you can test the mix ratio of the coolant.

I watched countless mot tests, they keep the car at fast idle for what seems an age until the readings pass the emissions - I wonder if the car suffered a bit of heat sink as your drove it, not getting enough cooling air through the system?

Ditto what Sean said. My car overheated a couple of times and the temp guage didn't show any problem until the idiot light came on and steam was coming from under the hood. Also, ditto on the water pump. If you don't have any record of it being changed, I would replace it. Not too expensive or difficult and the peace of mind is worth it. There are a lot of threads on this. I replaced mine with a metal vaned water pump, but there is some controversy about that as to whether you should get a metal aftermarket pump or the upgraded Jaguar one, but either way ...

Hi guys. I really do not know if an upgraded pump has been fitted, but as the car was first registered in December 2000, I honestly believed it had. I don't know how to go about finding out but if it helps, the vin number and engine numbers are available.
Sean, the test I referred to isn't the UK MOT test, but the Jersey pre registration test for imported vehicles, to ensure road worthiness. Sorry, I should have explained more fully. If the info re upgrade is not forthcoming from the engine number, is there a way to find out easily (ie without the use of a set of spanners etc.) I have registered with Jagwrangler Sean, and look forward to their updates.
Thanks so very much for your help guys. I do so want to get this car absolutely right. It deserves it.

Water Pump TSB
 

Richy, attached is the Jaguar TSB on the water pump. Maybe this will help. Cheers.

Hi Jimmy. Thank you so very much for that TSB. My VIN is well within the range for white poly phenol sulphide, not the nylon 66 that needs replacement. It also lists pump part numbers, which I shall check just to be sure. You have helped return this old guys nervous system to a normal state of relaxation. I shall now have a coffee to help me chill further. Cheers my friend.