So I just noticed that the coolant expansion tank on my 2000 Disco 2 is almost empty. Should the tank have coolant in it or is it an overflow tank? How much should it have in it? I always eagle eye my temp gauge while driving.

On another note I keep hearing a sort of fast ticking sound which doesn't seem to change when accelerating or revving in park. It is very annoying and now and then it will go from tick, tick, tick to a rapid ticking, often returning to the same tick, tick, tick before disappearing altogether . Any ideas.

 

Fill line on side of tank almost at seem. Find your leak
I use an auto stethoscope to find source of noises but a stick or little pipe works

 

x2 fill the tank, purge it, and put a pressure tester on it.

 

I don't actually have any leaks, knock on wood, my tank was just low. Today I was informed by a Rover freak that my head gasket has already been replaced. He has some of the coolest custom Rovers I've ever seen, Including a custom convertible 98 Range Rover HSE.

 

Water just does not get low. It went some ware could be bad or worse , get a ultra gage & see real water temps ,the factory Gage will go from no worries to red allert full melt down in about 3 secs ! Just sayin , blamo

 

It is possible that your expansion tank Let water out the overflow to a certain level below the line, but almost empty is definitely not a result of that.
Then again I am no Rover freak, but I have almost taking the top off my on a couple of occasions

 

If your cap is bad, coolant can leak out of the tank while you're driving down the road. Also, you might want to eyeball the throttle heater plate and anywhere else just to be sure there aren't any leaks. These engines don't like to overheat, and if you run low it's pretty easy.

How old are your hoses? Since summer is coming you might want to replace them all if they are original.