I have a 2007 XK base model does it have metal or plastic timing chain guides

 

Metal. The 4.2 litre engine has no issues in this regard...in fact almost no issues at all (apart from the thermostat housing with the integral thermostat. It should be changed as a matter of normal servicing, approximately when the transmission fluid is changed - every 50,000 miles).

 

Thanks, I have already had to change the water pump and housing part of the impeller blade broken. (plastic)

 

What was the trigger to change the pump?
loosing coolant?
Overheating?