I have a 1999 Jag XJ8 Vanden Plaus with 83,000 miles on the odometer, but from talking to the original dealer, I found out the engine was replaced with a brand new engine, from Jaguar, at 49,300 miles. This would mean there is only This would mean that the engine in the vehicle only has about 33,000 miles on irt. Unfortunately, the previous owner did vetu poor maintenance, and upon having the engine pulled and torn down, the knocking noise that was coming from the rear of the left rocker arm cover, showed the number eight cylinder connecting rod bearing to be badely worn. The oil was like sludge and the mechanic feels, since the the oil pump is in front, the rear cylinder bearings are the last to get lubrication. The good news is the bearing on the cylinder in front of the # 8, is perfect. Also, the crankshaft is perfect condition, even at #8. The tensioners all appear in good shape. The transmission oil was black and so the transmission is getting a full inspection and maintenance. Also, the water pump is being change to one with metal impellas and the therosatat housing is being upgraded.
My question is since even though the tensioners appear in very good condition (the engine is on a stand) and probably only has 33,000 miles on it. tensioners. is it worth changing only the secondary tensioners, as I have heard theses are primarily responsible for catastrophic failure and the timing chain skipping teeth, where the piston can hit and bend the valves. Secondary tensioners (metal Alloy) would be easy to change at this point, and the cost would be minimal...Thoughts Please

 

Yes, replace the old plastic tensioners with the metal ones. These plastic ones can go at any time. Plus the added strain on them of a poorly maintained engine.
The new plastic impeller water pumps are supposedly quieter and smoother than the metal ones.

 

If it currently has the plastic secondary tensioners, by all means replace them with the metal ones while it's easy to do so. If it already has the metal versions (you didn't state in what year the engine was replaced with new) then they are likely just fine.

The primary tensioners and chains have not been an issue.

 

I am looking for the tensioner where do I find the cheapest? I have been contemplating on replacing the whole system I have leaks from the front of the car so i wonder if gaskets have gone bad 122k is the current mileage I am the 3rd owner. please help? car