As with all auto engines, severe overheating problems can be very frustrating and nerve racking especially in hot weather and slow moving traffic. If not resolved it can be potentially very expensive! It’s critical to ensure your XK8 cooling system parts are in tip top order for piece of mind. Worse case severe overheating scenarios are; blown head gaskets, damaged cylinder heads and potentially a deterioration in engine lubrication quality. The latter can then affect the longevity of crankshaft bearings and the general life of the XK8 engine.
Prior to 2003 and the introduction of the 4.2 XK engines, earlier cars suffered from using poor quality parts in the form of lightweight materials. Relating to the water pump, this manifests itself in the disintegration / breaking up of the plastic impellor within the water pump. This then leads to reduced coolant flow, localised heating and the worst case problems mentioned above. Indicative signs of a cooling problem on the XK8 engine are the cooling fans staying on for long periods regardless of temperature and / or one of the top hoses blowing off.
Before going to the effort of removing / replacing the water pump, with a cold engine, take the filler cap off the expansion tank and then ask someone to run the engine for you at 1200 rpm. Should the pump be working correctly, water should be circulating / swirling well in the tank. If there is a problem, then there will be very little swirl and therefore indicative of a problem with the water pump. If you are going to the effort of checking it then it’s worth replacing with the latest XK8 parts including water pump and other cooling system parts.
Pre 2003 cars also suffered from breakdown of other plastic cooling system parts. These relate to the thermostat housing rising out of the block and the bridge pipe linking the cylinder heads on naturally aspirated cars (the XKR has an alloy pipe). The thermostat housings are now available in alloy and we hope that the bridge pipe will follow. The Jaguar Part number for the water pump is – AJ8008912 and all later water pumps supersede to this part number.
If you are going to the trouble of the above then we recommend you change the thermostat and check / replace all hoses as required.