Land Rover Repair: Ranger rover Se Misfire after driving for 15-20min and lose power, exhaust gases, combustion chamber

Question
Hi John I have a Range Rover Se 4.0 1998 and while i was driving on freeway 70mile/hour i felt the car was losing power so i pushed the gas little more but it was not picking up. I was hearing noice on exhaust misfire and was in 2000 rpm and 55 miles/hour Temperature was in middle as usual and as soon as i get off free way and stop the car dies. So i have to restarted and fast push the gas and drive and was no power what so ever So i get home park it and next day i started everything run smoothly but and get back in freeway and after 15 min driving it starts again. I know is not the gasket cuz no smoke coming at all I changed recently the wires and spark plugs. When is over heated i open the hood and i hear a click sound something i never heard b4 But only when car is been rinnung for more then 20min
Please help me with my problem
thank you for your time
sincerely
Claudio

Answer
Hi Claudio,

it sure sounds like a blown headgasket; misfires, loss of power especially when the engine is warm or hot.  The clicking noise is disturbing and could be either a bearing or (gag) indication that a cylinder sleeve has dropped.  No smoke does not mean that their is no gasket damage or that coolant is not leaking into your combustion chamber.  Blown headgaskets are common for these engines and they can either push air into the coolant and/or leak coolant into the cylinders.

Best to have local garage analyse the exhaust gases for the existence of coolant fumes.  An independent LR shop should be able to do the exhaust testing and then determine if its a headgasket or sleeve problem.  Headgasket replacement is about $2000 or so, liner drop means engine is ruined.  I hope its just a headgasket!!

Best of luck,
JohnMc