As with all car engines, serious overheating problems can be very frustrating and stressful, especially in hot weather and slow traffic. If not resolved, it can potentially be very expensive! It is essential to ensure that the parts of the cooling system of your XK8 are in perfect condition for your peace of mind. In the worst case scenarios of severe overheating are; burnt head gaskets, damaged cylinder heads and a possible deterioration in the quality of engine lubrication. The latter can affect the longevity of the crankshaft bearings and the overall life of the XK8 engine.
Prior to 2003 and the introduction of the 4.2 XK engines, earlier cars suffered from the use of poor quality parts in the form of lightweight materials. In relation to the water pump, this manifests itself in the disintegration/breakage of the plastic impeller inside the water pump. This then leads to reduced coolant flow, localized heating and the worst problems mentioned above. Indicative signs of a cooling problem with the XK8 engine are cooling fans that stay on for extended periods regardless of temperature and/or one of the overhead hoses going out.
Before making the effort to remove/replace the water pump, with a cold engine, remove the expansion tank filler cap, then have someone run the engine for you at 1200rpm. If the pump is working properly, the water should be circulating or swirling well in the tank. If there is a problem, there will be very little eddy and therefore indicates a problem with the water pump. If you’re going to make the effort to check it out, then it’s worth replacing with the latest XK8 parts, including the water pump and other cooling system parts.
Cars prior to 2003 also suffered failures in other plastic parts of the cooling system. These relate to the thermostat housing that protrudes from the block and the bridge tube that joins the cylinder heads on naturally aspirated cars (the XKR has an alloy tube). Thermostat housings are now available in alloy and we expect bridge tubing to follow. The Jaguar part number for the water pump is – AJ8008912 and all subsequent water pumps supersede this part number.
If you are going to bother with the above, we recommend that you change the thermostat and check/replace all hoses as necessary.
