FAILED 4.2 TOP TENSIONER, IS THIS A FIRST??

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robv12
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Joined: Fri Oct 30, 2009 10:11 am
Location: scottish borders

FAILED 4.2 TOP TENSIONER, IS THIS A FIRST??

Postby robv12 » Sun May 14, 2017 2:38 pm

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
Attachments
350 tensioner new.JPG
350 tensioner 3.jpg
350 tensioner 2.jpg
350 tensioner.jpg
88 3.6 XJ40 EX JDHT
88 3.6 XJ40 SOV
93 XJ40 XJ12
94 XJ40 3.2 Majestic Gold
94 XJ40 Daimler Majestic Insignia
93 XJ40 XJ6 3.2 paint test car
97 XJR 300 Manual
97 XJR 300 Manual EXJDHT
55 XTYPE EST 3.0 SP PREM
62 351 LWB PREM LUX

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J44EAG
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Joined: Sat Oct 20, 2007 9:57 pm
Location: Warlingham Surrey/Faversham Kent

Re: FAILED 4.2 TOP TENSIONER, IS THIS A FIRST??

Postby J44EAG » Sun May 14, 2017 2:52 pm

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
X350 Co-ordinator

2004 XJR

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robv12
Posts: 2052
Joined: Fri Oct 30, 2009 10:11 am
Location: scottish borders

Re: FAILED 4.2 TOP TENSIONER, IS THIS A FIRST??

Postby robv12 » Sun May 14, 2017 2:58 pm

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

ptjs1
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Location: Kent

Re: FAILED 4.2 TOP TENSIONER, IS THIS A FIRST??

Postby ptjs1 » Tue May 16, 2017 11:49 am

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
1995 XJS 4.0 Convertible
1980 XJ-S Pre-HE
Jaguar 4.2 Supercharged engine (but not with a Jaguar body..)


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