Engine Cooling problem
1998 Citroen Saxo 4 cyl Two Wheel Drive Manual 140000 miles

hi there basically when driving normal engine temp is fine sits dead in the middle no prob. when i drop a gear and accelerate hard the engine temp goes up from the middle mark but does not reach the red quite. then as soon as i stop accelerating hard the temp comes back down quite quickly to normal. its only under hard acceleration the level is fine and doesnt leak or need topping up the thermostat is brand new as is engine headgasket and also had a new water pump. any ideas thanks