Ye olde ‘Coolant Low’ warning

[MaxTheDog]

Hello All,
Apologies if this post seems a bit of a waste of memory space and server use, but yesterday I got the ‘Coolant Low’ warning. I was about 5 miles from home. I switched the engine off and restarted and didn’t see it again. Looking in the manual at checking the level it mentions an upper and lower level. However, on my black opaque tank I cannot see any level marks, not that they’d be of much use! When I’ve taken off the filler cap (cold engine!) the level is about 1.5 inches below the top of the tank ( not the top of the filler).
Assuming the sensor hasn’t got stuck, for future reference where is the correct level and why use an opaque tank?
Car is a 2000 XK8 coupe.
No leaks seen under the car or anywhere in the engine bay.
Thanks,
Michael.

[Lucky]

I was told to fill up to the base of the filler cap.

It could be your thermostat housing has a crack in it, in which case the liquid would evaporate from the heat of the engine before you could see it drip anywhere. Look at the front of the engine 'V' and you may see something. If your thermostat housing is plastic then it is probably the original and in need of replacement. The later ones were aluminium.

[MaxTheDog]

Thanks Lucky will check that. A replacement ‘stat housing is on the list!
M.

[Lucky]

I would top it up first and then keep an eye on it. If you are still losing coolant then get it checked over by someone who knows what they are doing. Replacing the thermostat housing isn't a cheap job.

[MaxTheDog]

Thanks again, Lucky.
It’s going to my Jagman on Thursday for the two front ABS rotors changing so I’ll mention it to him then.

[Astromorg]

I thought those front rotors that double as nuts to hold the front hub in place were virtually indestructible in service. What happened to need their replacement They're not cheap

[aaj]

Michael
There are no upper & lower level marks on the Coolant Expansion Tank. The Coolant Level should be level with the bottom of the Filler Neck.
All the various plastic parts of the cooling system are known to fail due the heat in the engine bay (they get brittle). The various pipes (particularly the ones in the 'V') soften with the heat & age. Also look for signs of a leak around the Radiator Pipe Stub welds.
AllanJ

[MaxTheDog]

Thanks to all for your respective replies.
Astromorg, apologies for the late reply. I had several ABS/Traction warnings and after finding the negative terminal on the battery loose and tightening it up they were still there. I’m a very new owner of this Jag and I’m erring on the side of caution. They were both changed and it’s not happened since.
As a continuation of the original subject, I’ve just driven from home to Moreton-in-Marsh(150 miles) mostly with the ‘Low Coolant’ warning on. So it’ll be topped up again tomorrow and further searching will be done when I’m back home. Hopefully under my own steam and not on a wagon….
Cheers,
Michael.