My 1.6tdi octavia is currently overheating when under load when idling will happily sit at 90c with fans running but will jump up and continue to climb when revs are over 1500, any ideas what might cause this? Many thanks in advance.

48 minutes ago, Richardbragg said:

any ideas what might cause this?

Water pump, since some "simply clever" 'sole made it do the job of both a water pump and a thermostat.