As said in the article, the only way to find out what tensioners are fitted in your engine is to remove one of the cam covers. There is no other way of seeing them. I would have thought it very unlikely that an engine that had tensioners fitted in 2006 would have the ali units fitted unless the fitter was knowledgeable that the ali types were then available.
I don`t think the new ali tensioners were fitted to 4.2 units until MY52. So the ali units would have been on the shelves in 2006 but whether they were fitted in 2006 to your car is the big question which only inspection will reveal. Perhaps another member can remember just when the ali tensioners first came to our notice.
As regards the primary tensioner and the two plastic slipper guides is concerned, although the slippers do crack, they do not suffer from regular and known failure be able to the same monotonous degree that the secondary or top tensioners exhibit. They are under vastly less stress than the secondary units and despite the odd crack are known to be good in most instances for well over 150,000miles. However there may be the odd exception to the rule.
- Cracked V8 primary chain guide 162k miles.jpg (53.77KiB)Viewed 2619 times
There is only one plastic primary tensioner and four long plastic slipper guide arms in the primary timing gear. The tensioner survives without issues at quite high mileages. Although as just said, the slippers can crack and still survive to seemingly high mileages. Neville Anderson at North East Jag Spares has developed an aluminium based kit as an option for when high mileage engines need overhaul. If that mileage is ever reached with your car at that mileage, then you might consider replacing the tensioner and slippers with his kit.
It is very unlikely that on a V8 with only 70k miles run, that you would need to replace the primary tensioner and slippers at such a low mileage. My S has covered 77k miles and I have no intention of opening up my engine for at least another 77k miles before replacing the primary parts. I think you too can sleep easy on that score.
Finally just reverting to BB`s article in the July 2012 magazine once again, my comment at the conclusion is worth revisiting once again. A quiet front end on a 4 litre V8 means little unless fitment of the third generation secondary tensioner type is known. Plastic tensioners on even a quiet engine can fail in a split second and wreck an engine in the same time. There are often no early warning signs that such a disaster is about to occur although some owners have been fortunate and had some indication that something was not as it should have been.
Sadly, it is a case of bite the bullet and find out just what secondary tensioners are in your engine. If they are plastic then best advice is to replace with the aluminium units at the earliest opportunity. Again Neville can supply those items at good prices.
Mike
