This may be a stupid question but here goes. Before parking the car for the winter last weekend I got an oil change
and radiator flush as part of the cars winterization program. I then took it for a 250km drive before I put her to sleep.
On the way back the temperature gauge started to drop and went to the bottom quarter section of the gauge. I was
pretty close to home so I slowed down to the city speed limit and the temperature started climbing back up towards
the middle of the gauge and by the time got home it was back near the middle. The temperature outside was just
above zero and I was going fairly fast. Would this indicate a problem, either coolant or thermostat? I've been looking
through the forum but haven't found much. Thanks.

 

There's NEVER a stupid question about cooling on the Jaguar V8.

Your forum search will probably have found many threads discussing:

1. the gauge is useless
2. the usual failure is not indicating overheating before it's too late

The only solution to this is to monitor actual coolant temperature and one of the best ways to do this is JagWrangler's RealGauge.
XK8 / XKR / XJ RealGauge - TheJagWrangler

Possible causes of the issue you experienced:

1. faulty temperature sensor
2. faulty gauge
3. sticking thermostat (most likely open as closed would tend towards overheating)

A failing water pump or low coolant would both produce overheating and neither would be temporary in the way you describe.

Graham

 

An affordable option is the Autool X-60


while not as elegant as the real gauge trio, the X-60 can be configured to display many of the engines activities, including coolant temperature, oil temperature (my favorite), battery voltage, MAF g/s, fuel trims, etc. The list is very extensive.

I’ve had mine a little over a year, can’t imagine doing without it now.

Z

 

Hi GGG and zray. Thanks for your responses. I was wondering if this was a sensor or thermostat issue. After reading a few posts about the
Jaguar gauges I have been thinking of getting the JagWrangler real gauges. I would like to keep the car looking as original as I can so this seems
like the best option. The instructions on the website look pretty straight forward and I've opened up the instrument panels to replace the light bulbs
so that part should be fairly easy. I'm coming up to my winter layoff and I've decided to take a basic mechanics course at the collage so I can do
some of the maintenance work myself and I'll add this to my winter to do list.

 

+1 to GGG,

Ozbot - You're right to be concerned. Overheating an AJ-V8 engine is a car killer as the low market value of our X100 cars, makes engine repair/replacement not cost efficient.

There have been reports that the car temp sensor can sometimes be "in the air" if coolant levels are low in the sensor/pipe connection and so the temp sensor isn't immersed in coolant. So, as I'm a big fan of zero dollar fixes, I would check your coolant level is full in the reservoir, and that the tank cap is tight. You may even have a leak somewhere.

 

Hi David. Thanks for the suggestion. I just had the rad flushed and refilled with -40 antifreeze for winter storage so maybe there was
an air lock or bubble somewhere in the system that came loose on the drive. I'm replacing the hood / bonnet support struts tomorrow
morning so I'll check it then. As for blowing the engine being a car killer, at this point in the game I would probably buy a wrecked one
with a good engine and swap it, using the rest as a parts car. Something for me putter with / learn on when I'm not working. Maybe
something like the cheaters.