VT Overheating Problem

[Eskimo79]

Can anyone help me with my overheating problem?

Recently while ive been driving the temp gauge has been going up.

It will go all the way to maximum on the gauge and display 'HOT' on the display.

After a few minutes, it will go back down if im driving. When I check the radiator and engine they aren't even hot. Im not losing any coolant either and both fans are working ok.

Ive had the thermostat replaced just to be sure but its still got the problem.
Under a pressure test a very small leak was found in the intake manifold gasket.
Could this be the cause of the problem?

Ive taken it to a few mechanics but they seem stumped.
Any help would be greatly appreciated people!

Cheers