Is the thermostat housing cover one of those plastic parts that can crack and leak? I am not sure if I have a leak from the hose or the hose connector. (if plastic)


I hate wasting money but in this case it might be worth buying both if the part is plastic.

 

I bought a metal one just to have it in case. Unbelievable the amount of junk plastic in these cars.

 

True that! Plastic timing chain tensioners for a start. Junk for sure.

Many of these original high failure parts have been replaced by metal ones; as even Jaguar acknowledged that plastic was a poor choice to begin with.

 

The plastic thermostat housing is indeed susceptible to warping, cracking, and leaking. The leak in my wife's XK8 exactly one year ago resulted from a warped thermostat housing. I nailed it down with a pressure test kit loaned from Advance Auto Parts. After doing the research on the XK8 forum and getting good advice from other 4.2 engine owners, I opted to replace the entire black plastic cooling outlet duct assembly and be done with it. No issues since....

 

Thanks Jon89 for the info on doing a pressure test. Is the thermostat outlet removed from the car and then tested?

 

No. You utilize the appropriate cone-shaped adapter from the pressure test kit that fits snugly down into the coolant reservoir (after removing the reservoir cap) and pump it up using the kit's hand pump. Your leak will become obvious (and usually enlarges) pretty quickly, so park the car where you plan to effect the necessary repairs before you perform the pressure test. Once you've done the pressure test, it's a good idea NOT to crank the engine again until you have completed the repairs....