Try these suggestions;

Make sure the radiator is properly flushed out and check for any cold spots. (i.e. blocked core).

Fit a separate fan switch giving you more control when approaching traffic.

If possible fit a 78 or 82-degree thermostat with a couple of hole’s drill in it.

Try fitting a 4x4 Sapphire fan switch it’s the same thread as the Rs turbos. This switch cuts in at 86 degrees and cuts out at 77 degrees.

Make sure the fans rotating in the right direction

Make sure the header tank cap is sealing properly, if not the pressure will drop causing the car to over heat.

It’s advised to have the car set up on the rolling road to optimise all settings (i.e. boost pressure, fuelling & ignition). If your cars running a weak mixture can also cause the car to run high temps


Hope the above info helps in some way