Hi Guys

I have a series 2 rs turbo, within 2 mins of the engine running the temp gauge goes straight pass the red when the water is still cold but does not overheat the car, I have changed the temp sender switch ( white and vilot) , I've tried a uprated thermostat ( 82c ) and uprated fan switch, I have tried 3 different sets of rs turbo dashboard gauges, checked the resistance between temp sender switch and gauge and all is good.
When the car has been run there seems a lot of pressure in my spec r header tank and can hear it boiling in the tank, it has had a new head gasket a month ago

Any help would be very grateful as its making go mad

Cheers Dave