Are the first and second stage cooling fans working ?
To check the second stage cooling fan is working if you turn on your AC while the engine is running the fan should cut in after a little bit to cool the AC rad.
To check the first stage disconnect the black plug for the rad fan there are there wires ( plug located near bonnet latch on chassis leg rh as you look at the car)
Go between the brown wire and one of the red wires you looking for continuity if it ok good do the same with the other red wire if this is ok good.
If one of the wires has no continuity you need to have a look at the fan resistor.
If the fan does not cut in when you turn your AC on look at your fuses and relays in the engine bay fuse box.
If all of this is ok test your water temp sender you can do a resistance verses temp test. your fist stage fan should cut in at 105 deg c coolant temp.
Make shore your supercharger belt is ok you should have one hole visible on the locking tang if not it needs changing as you know if the belt is slipping it will not drive the sc which drives your water pump.
Failing all that you need to pull off your water pump and check the oil in the water pump drive end of the super charger the seals fail in the sc and then the oil is drawn in to the sc and then the gears run dry and wear out and cause cooling problems
Have a look at this link post 304 http://www.northamericanmotoring.com...r-pump-13.html
Hope this helps