Ok, from my searching online and of this site, I have seen that some people say the expansion tank cap should have a seal on it.

So, as my vrs leaks a little coolant very slowly, I figured my missing seal on my cap would be the problem. So, I ordered a new tank/cap . . . and it arrived today, and yes, it has no seal on the cap either!

Basically, should the cap have a seal or not?

Anyone know for sure what the answer is?

Extra annoyed with it all now, the new cap doesn't even fit like the old one, seems to sit and 'lock' higher up on the thread, leaving a fair gap. And after doing a long run yesterday, my water light came on this morning . . . No obvious leaks under the car either.

I don't think water would come out the cap. Warm the car up and then slowly unscrew the cap a little way. If you start to hear air come out you know it is a water and air tight seal like it should be.

If you can not see any evidence of leak at the end of pipes like coloured corrosion. Or any signs of water in the oil. Or any signs of the heater matrix leaking. Then put some radiator sealing chemical in from Halfords or Tesco. Use the heavy duty stuff designed to fix small head gasket leaks. I would put the old cap on too.

Bearing in mind that the water pump runs at the speed of the engine. So when driving along the flow and pressure of the water increases. The extra pressure may be needed to push the water out the loose pipe. So the leak may not exist when you are looking for it when the car is stationary.