The AJ133 is a great engine. No doubt about that in my mind. A Jaguar UK design with no Ford engine components. But it has received some criticism for problems that have raised their ugly heads relating to the camshaft timing chains and associated components. I have personally fixed and rebuilt 4 of these engines, working on the fifth now and felt I needed to document and share what I had learnt as, as is usual with Internet related stuff, there seems to be a lot of misinformation out there.

Basically there are two distinct designs of timing components. One is based on the Tsubaki timing chains and one on the INA chains. The chains look very different. The pitch of the chains is even different, the Tsubaki having a pitch of 6.35mm (¼”) and the INA 8mm. Most people seem to assume these dimensions are the width but they are in fact the pitch. The Tsubaki chain is actually quite a bit wider as can be seen in the photo below:


INA chain top (Part # C2Z22078), Tsubaki bottom (Part # AJ811429).

Tsubaki System

As far as I know the Tsubaki system was only used on early Jaguar variants of the 5.0 fitted to the XF and XK, mine was certainly that way but I have no way of confirming that. All Range Rover variants that I have worked on had the (later) INA system.

I was told by various people that the design was changed to the thinner INA system because the Tsubaki chains were found to be stretching, I can’t see that myself have held both in my hands. I think the change was cost cutting, Ford influence, but who knows.

Everything is different about the two systems, the chains, tensioners and guides. So let’s look at the Tsubaki system first……

Here is a moveable guide (Part # AJ811499) :





Notice the plastic insert for the tensioner to push against.

Here is a tensioner (Part # AJ811499) :



Notice the ratchet teeth.

And here is what the installation looks like:


I put new fixed guides in this 120K engine as they had some slight cracking, everything else, including the chains, appeared fine, so went back in, as I was concerned the engine was toast for other reasons. It wasn’t and still runs strong.

I believe this is the first design and was only fitted for a year or two, again Jags only.

INA system

For whatever reason the design was changed to the much cheaper looking (in my eye) INA system. Where the plastic insert was in the moveable guide of the Tsubaki system there was no insert on the INA system. The tensioner plunger just contacted on the aluminium (I’m British) of the guide.

This turned out to be a problem as the steel plunger of the tensioner bored a hole in the aluminium in time.



This caused the system to run out of adjustment and the chains to go slack, this allowed the chains to eventually slip and the timing to go out with potentially catastrophic results when the pistons hit the valves, as displayed by this engine I dismantled:



This problem I believe has caused most of the failures and caused the bad reputation.

At some stage soon after the initial redesign, around 2012, the design was further modified. A steel rivet (for want of a better description) was incorporated into the moveable guide for the plunger to push against so that steel rubbed on steel. I’m not sure why they didn’t go back to plastic but I’m sure they had their reasons.

Here is the modified guide alongside the original :



There have also been at least two designs of INA tensioner, with differing upper mounting hole locations, thus changing the rotation of the tensioner as shown below:



Upper Part # FX23-6k254-AA, lower 8W93-6K254-CA

Plunger location and design is also different:



I don't have any old parts to inspect currently but it looks as if the FX23 variant had a single ratcheting hydraulic piston and the 8W93 had inner and outer pistons, one ratcheting and one hydraulic, I need to get hold of some and check that.

I noticed on one of the engines I dismantled (crank seized due to lack of oil - why no oil pressure sensor on this engine - crazy) that the 8W93 version was fitted and the plunger angle relating to the guide did not look correct, not pushing square to the guide:




So when I rebuilt this engine I fitted the FX23 variant which looked much more correct:





The casting hole was moved to alter the angle at some stage. Or had incorrect tensioners been fitted at some stage? Both part numbers seem to be advertised as suitable for the AJ133 engine.

Summary

The two systems do have different variators because of the chain differences:



And they do fail:




Having looked at all the components carefully it seems to me that the Tsubaki system is the better engineered. I suspect the design was updated to save money. Not sure what the deal is with the two types of tensioner, maybe some engine blocks have mounting holes in different positions. That’s all I know for now, comments and factual corrections/additions welcome !

 

Admin, can you make all the photographs smaller ? I couldn't edit the size.

 

Excellent review. Very informative.
Would this also apply to the AJ126 V6 SC engine? or was that engine always with INA chains?

 

Good question.
My understanding is that the AJ126 got the INA chain/system from the get-go (mid 2012 I think), all I know for sure is the AJ126 in my Oct 2014 build F-Type definitely has the INA chain.

 

Awesome write up - since you've done 4 of these jobs, how would you estimate the time it takes? Asking for a friend who has a V6 and V8 who might end up doin this to them one day

 

All the engines I have worked on have been removed from the vehicle.

 

Great info, thanks.

My research yields the following for engines with the INA chain set:

Timing Chain Tensioner AJ813898 / LR095472
Timing Chain Blade C2Z28431 / LR051013

I’m very curious about the 2 different tensioners that you highlighted, with the different mounting positions. In the parts information that I have, all previous versions of tensioners are superseded to the numbers I quoted above, i.e. only a single model, not 2 models with different mounting positions.

 

I have been told that you would get a CEL for cam disagree before catastrophic failure. ?
The class action settlement covers 2012-2014 motors. I think I read that they made a change to 2015 and up timing chains. ?

 

There is no class action case/settlement. Plenty of other threads relating to failures, please keep comments specific to parts and modifications, trying to collect factual info on this one. Thanks.

 

Thanks kansanbrit great explanation and pictures!
One question about the early setup as it looks like the tensioner plunger acts directly on the rubber/plastic part on the back of the guide shoe?
Surprised that held up since the steel pin wore into the Aluminum part?
.
.
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Yes, correct, and I saw very little wear so can only assume the very slippery surface of the lubricated plastic prevented chaffing.

 

I suspect that the tensioner part # 8W93-6K254-CA is for the Tsubaki chain system, not the INA. The jaguar part # for the Tsubaki tensioner is AJ811487, and doesn't have any supersessions. Web searches on these part numbers don't yield anything conclusive. It's possible that the engine you show in the pics above with the 8W93-6K254-CA tensioners, somehow had the Tusbaki tensioners with the INA chain system.

 

A question for you kansanbrit:
That little plate I can see on the outside/front of the tensioner (not sure what it is for, my best guess is that it held the grenade pin in place) is not there in later versions, and that plate sure looks like it could potentially rattle a fair bit. Could that be the main source of "rattling timing chains" in the early AJ133???

 

the new design is terrible. hell i had a 15 wallet rover autobiography jump time just idling in the shop


you stick the 90 degree down the fill hole and if it flops around somebody’s wallet got lighter

 

That plate will rotate to release the ratchet to to push the piston back in, also holds piston in with the pin during assembly. It can't rattle around. Similar tensioners were used on the 4.2L like this one:

 

I have some more info to add regarding the design of the INA hydraulic tensioners. I recently completed the tensioner/guide replacement on my 2013 XJ 5.0 SC which was exhibiting unusual engine noises. I have done many of these jobs so it has no surprises for me - apart from this one.

I always assumed that there were only 2 designs for the tensioners on the INA system. But I discovered a third intermediate design on my car as can be seen in my photos and the suffix on the part number confirms that it is a different variant. (the third photo is the latest design).The plunger on this intermediate design is the same as the plunger on the latest design but the body of the tensioner is of the original design. The motor has definitely not been opened before so its not as if its a DIY work around for the original poor design. The guide rail appears to be identical to the old design.

Has anyone encountered this before?

 

Here goes my thread down the toilet. Keep on topic PLEASE.

 

Kansanbrit - very sorry about that. I have messaged a mod (GGG) and asked that my posts and the one above be moved to a separate section to keep info here tidy.

 

I've removed RobThe**** 's series of posts which leaves the thread topic on track.

Graham

 

I pulled some of those CB variant out of a 2012 XKR engine I am working on currently and they had drilled a nice recess in the older design guides.