my 140y was overheating 2 days ago, above the high mark of the car, not sure wats causing it, as the radiator is full off water, had my radiator recorded about 2 months ago to a 3 core, taking my water capacity up from just over 2 litres to over 4 litres, surely there is enough water, almost half gets lost, i see no leaks, I believe my thermostat has been removed also, I'm thinking its the waterpump that has the problem. Also when I filled the water up and ran the engine, bubbles appeared big ones and also small ones making a bit of a frothy look. Any ideas?

sounds like head gasket gone

It's very possible, I'm meaning to change all the gaskets on my engine.
But its only gotten this bad the last week, what could have caused the problem in the first place?

I would say definitely head gasket

BUT WHAT COULD HAVE CAUSED THE HEAD GASKET TO GO?

they just go after a while...no real reason most times its just one of those things, but you should have a thermostat on anyway. but if you have it in bits check the head for corrosion and check the water pump and see if the it works

As above!

Have you checked under your oil filler cap? If it looks like a cappachino under the cap then probly head gasket is leaking or head needs needs some work.

WILL HAVE A LOOK, BUT NOTHING LAST TIME I CHECKED

When was the last time the head gasket was re-torqued? Datsun owners manual says to do it every 12 months or 12000 miles.