Timing Chain Tensioner Replacement

[J44EAG]

The subject has been debated at length by members in our monthly magazine, in the various Jaguar V8 Forum pages and on the appropriate Forum BB sites.

A stitch in time with V8 tensioner replacement can save the costs of an engine rebuild if replaced in time.

The problem stems from the use of plastic bodied tensioners and the effect of stress reversal loads inparted by the phasing of the camshafts dictated by the design of the engine. Plastic tensioners are a known weak point in the V8 and modified aluminium tensioners are now available as direct replacements for the original units.

If an owner of a V8 cannot find documentary proof that the modifications have been effected, then he is strongly advised to investigate the true status of his engine at the earliest opportunity. Failure is often sudden and without any prior indication that failure is about to take place.

Full pictorial and text details of the work required may be found on the XK8 Bulletin Board under the headings of "Engine" and a post entitled "I changed my timing chain tensioners yesterday". The change proceedure is fully documented and interesting questions and answers accompany the explaination.

Highly recommended reading.

Mike kennedy S-type Co-ordinator.

[willgolledge]

I had the dreaded top tensioner failure recently resulting in a broken exhaust cam chain ! However removing the cam and carrying out exhaustive pressure loss tests all cylinders held high pressure! I reasoned that there was no valve damage and stripped the chains and tensioners. The lower tensioners were also plastic and splitting and the chains stretched considerably. On refitting though my engine has VVt units or cam position actuators as the info calls them. The fitting instructions say they have to be fully retarded before tightening the cam bolt. This makes sense except the special pin tool does not fit the bores! Either the tool is for an earlier version or badly made? Autodata and Sealey merely state refitting these VVT units and make no mention of setting them up. Does anyone have the answer? Are these units retarded by default and oil pressure advances them automatically? I would like the info to be less vague before bolting the beast back together!! Many Thanks

[J44EAG]

Hello Will.

This is what the Jaguar Technicians Overview publication says. Copies available from Derek Boyce at JH for around a tenner.

"With the oil control valve open, oil pressure on the helical drive piston is increased, rotating the cams to the advanced position. When the valve closes, oil pressure reduces and the return spring pushes the piston back to the fully retarded position".

Hope that helps.

Suggest you contact Ian at XJK for professional advice with the tool. Ian`s details can be found on the S-type Forum pages in our magazine.

As previously suggested, there is masses of discussion info on the XK8 and X308 Bulletin Boards. Somewhere on those boards, one of the members, possibly Brake Buster, posted an excellent run of photographs on how to do theses tensioner changes. If only I could find the posting! I`ll keep looking!!

Please let us know what you find out.

Rob V12 - can you help with the tool query or remember where that rake of photographs were posted?

Mike

[willgolledge]

Many thanks for the info; I did indeed read lots of posts and checked out the photos of tensioner/ chain refitting, unfortunately for me and fortunate for them none were fitted with vvt units. There was a suggestion that the o rings should be replaced prior to fitting which is sound advice.
The tech info would seem to confirm that these units are sprung-loaded to the retarded position and therefore do not require interference; presumably why the old VVT tool doesn't fit! The issue could well be academic if my assessment of the exhaust valves is wrong- but I think it worth a go to try and save the engine!