www.jec.org.uk

we all know the problems with 3.2 and 4.0 top chain tensioners, and the work around to cure the problem, fit the 4.2 alloy version and upgraded bolts, job done, no more problems

or is it, recently I was asked to look at a poorly 4.2V8 with a distinct rattle, the owner took the car to a well known local garage who removed the cam covers, to find a loose chain on the right hand bank

on strip down the bottom of the tensioner had parted company, a luck escape for this owner, its the first failure I have seen

pictures attached with broken 308 items to compare and a new alloy unit as it should be

The first issue I`ve heard of Rob. Rather a concern, I think. I really thought we had seen the last of this type of problem.

What mileage was on the engine? Had a good oil change record been maintained?

Of course there will always be occasional problems with manufacturing quality with many parts. This may just be one of them....or may be not. There could be other issues with this particular engine which may have placed an excessively high spike load on the drive train which has lead to this unit failing. Ideally, the missing slipper plate needs to be recovered to see what type of failure has taken place.

These secondary tensioners have a hard life. The two plane V layout and V block angle of 90 degrees lead for difficult and uneven valve opening sequences and spike loading of the camshaft gear. It isn`t an even running train by any means. Hence the stress reversals which cause these dreadful problems. Will this issue be shown to Jaguar for comment? I think it needs to happen.

Mike

Mike

car is a 2005 Supercharger with 150K ish miles, good history, car is not back with owner yet, so work to replace is in progress, will ask for the slipper parts when retrieved

Rob,

With the mileages that some of us have done on these 4.2 engines, you'd have to assume at this stage that it's a really rare manufacturing defect that has caused this, rather than a worrying failure trend. As Mike says, the orientation puts quite a load on the tensioner but we also know that many cars will not have had the disciplined oil maintenance regime and yet we've still not heard of a failure. It's unfortunate for the owner and would be interesting to hear your views when you've seen it, but I think (and hope!) it's really a one-off.

Paul