I was told by the Jaguar Dealership, that my '98 XJ8L 4.0 needed replacement of my tensioner. This was due to engine clatter that goes away once warmed up. I bought the tensioner online and had my own mechanic open up the crankshaft only to find out there is already a third generation tensioner that needs NOT to be replaced. My mechanic suggested that I replace the entire primary timing chain assembly. However, he is not a certified Jaguar mechanic. So he too may be blowing smoke up my you know what. So my question is, instead of replacing the primary chains, can't they just be adjusted? Or perhaps, I can live with a little bit of rattling.

 

The people on this forum probably have no idea what you are talking about.
You have an X308 car and need to post this on the correct forum.

That being said, The primary tensioners are plastic body like the secondary units that fail and the lower chains rattle just like the upper chains. The early model primary tensioners are hydraulic only and when the 'O'ring and/or the lower piston fails and leaks, then the tensioner blade 'RATTLES'. The newer metal body tensioners are of the 'RATCHET' type and once extetended, they will NOT RETRACT unless the unlocking mechanism is operated manually. The original chain guides and blades are probably broken/cracked so a complete teardown is the only way to know how many components need replacement.

bob gauff

 

Moved off to the proper forum

 

Your mechanic is giving you good advice. Be safe...replace all 4 tensioners and guides now. If/when a tensioner fails, it usually is catastropic; i.e., valves make contact with pistons...engine is trashed.