As with all car engines, serious overheating problems can be very frustrating and distressing, especially in hot weather and slow traffic. If not resolved, it can potentially be very expensive! It is critical to ensure that the parts of your XK8 cooling system are in the best order for your peace of mind. In the worst case, there are severe overheating scenarios; Burnt head gaskets, damaged cylinder heads, and 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.
Before 2003 and the introduction of the 4.2 XK engines, previous cars suffered from using 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 on the XK8 engine are cooling fans that stay on for extended periods regardless of temperature and / or one of the upper hoses blowing.
Before making the effort to remove / replace the water pump, with the engine cold, remove the filler cap from the expansion tank and then have someone run the engine for you at 1200 rpm. If the pump is working properly, the water should be circulating / swirling well in the tank. If there is a problem, there will be very little eddy and therefore it will indicate 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 parts from the XK8, including the water pump and other cooling system parts.
Cars prior to 2003 also suffered failure of other plastic parts of the cooling system. These relate to the thermostat housing that rises out of the block and the bridge tube that connects the cylinder heads in naturally aspirated cars (the XKR has an alloy tube). The thermostat housings are now available in alloy and we hope it will follow the pipe from the bridge. The Jaguar part number for the water pump is: AJ8008912 and all subsequent water pumps supersede this part number.
If the problem from the above is to be taken up, we recommend that you change the thermostat and check / replace all hoses as needed.