I have been enjoying my 1999 XJ8 trouble-free so far, reading here and learning much.

With 76kmi. on the clock, I am thinking about timing chains. It is my understanding that if the tensioners go, there is noise to warn that they need to be replaced. I have this from the Christopher's Foreign Autoparts website, as well as posts I've read here. Apparently, the chains themselves rarely fail catastrophically. Is this correct? Should I replace my tensioners as preventative maintenance, or wait for the rattling noise? I hate taking stuff apart when it is working perfectly.

I have seen the tools needed to fix the cams and crank during the replacement procedure because "there are no timing marks". I have changed timing chains on other engines with similar design that do have timing marks, and it is very easy to line everything up. Without addressing how these marks would be made, why wouldn't simply adding timing marks work on the Jag engine as it does on other engines of this type? What am I missing here?

Thanks for your replies in advance.

 

The timing marks you use on timing chain replacement are the missing tooth on the crankshaft timing target gear teeth and a mark inside the valve cover on the cam gears themselves ( 4 ) . Looks to be the flats as a tool is placed over them . You can eyeball the cam marks without the special tool as one tooth off on cam gears will be visually obvious . Yours I believe does not have VVT

 

"Apparently, the chains themselves rarely fail catastrophically. Is this correct?"

In a sense, yes. The secondary chains just jump the teeth on their sprockets, allowing the exhaust valves to fail catastrophically as the pistons smash into them. The chain itself usually remains fine in this scenario (but not always). My 2nd-generation plastic secondary tensioners were severely cracked but made no noise before I replaced them, which is how the 2nd generation tensioners are designed (the internal spring allows no chain rattle, even if the tensioner is 99% of the way towards total failure).

I would not use noise as a guide. Replace your tensioners.

 

Instead of timing marks Jaguar use a service position on these and current units. The correct tool-set includes a dummy crankshaft sensor to lock the bottom end in position at 45 degrees after TDC. Also included are the two cam locking tools, once these three items are in place the guides and tensioners can be replaced without issue.

Along with this preventative work consider the trans-go valve kit for your transmission and research the service procedure. These 2 jobs will be wallet/stress savers.

 

The reason the Secondary Cam Chains fail 'catastrophically' is that the plastic 'shoe' or 'slipper' dislodges from the failed tensioner and gets caught between the chain and sprocket. The diameter is increased and stretches the chain to the breaking point.

Sometimes the chain wraps around the intake cam sprocket and pushes a section of the cylinder head OUT!!!!!

Sometimes the exhaust cam stops in a BAD PLACE and the valves get BENT.

Sometimes the exhaust cam stops in a HAPPY PLACE and all that is required is to install new chains.

I have seen ALL 3 of these scenarios.

Good luck.

bob

 

I'm not a big believer in luck when it comes to cars. I come here for the voice of experience and I always find it. I'll order my chain tensioners and change them over the Christmas break.

So there is no reason to use the locking tools, as long as you establish a reference for the positions of the crank and cams. I saw no way that this could not be the case.

 

I've never done the job , just my advice . Before changing it over get the shop manual to ensure that you have the setting point of the crankshaft position with reference to the camshaft as you don't want to be wrong on this for valve / piston interference . The crankshaft only rotating at half the speed of the crankshaft you can be one rotation off and have catastrophic results if referencing the external observed angles only .

 

The secondary tensioners can be replaced using the 'ZIP-TIE' method.
Much info on the internet and this forum for that.

bob

 

Yes, I've watched the zip tie method videos. Looks great. Of course, that's just half the job though. I've read conflicting advice regarding replacement of the lower chains and guides, although I don't really need the advice. I'm just looking for justification for my laziness. I think we all know that the only way to do it right is to replace the whole mess and be (hopefully) done with it.

I'll just get the whole kit and do it right.

How is the quality of the parts sold by Christopher's Foreign Autoparts? I've seen nothing but good reviews on his stuff. It's supposed to be the same parts you'll get from Jaguar, but ?? Anyone seen them side by side?

And Lady P. - yes, absolutely. I'll get my references before I take things apart, so I know the timing is right and I'll be able to see if anything moves. I think the fixing tools are for speed and security, not really necessary tho.

 

I was searching E-bay for the timing chains/tensioners kit and came across a listing for two secondary tensioners with chains for $9.95. They are aluminum. I ordered them on a lark - just to see what they look like. I'll report my findings when I get them and compare them to the parts I get for the car.

 

The major task with new tensioners/chains is getting the crankshaft pulley off. You have to deal with 360 - 380 Nm in a fairly tight space. When you're done with the bolt the pulley still waits for you. You can't get that off without the special tool IMO.
Don't underestimate.

 

Don't go cheap on something this critical . A relay maybe .

 

Thanks.

I had case no. 2 with two unlucky exhaust valves snapped in half after the slipper (LHB) went through the sprocket and the chain snapped.


LH secondary tensioner slipper after going through the sprocket.




RH secondary tensioner doesn't look much better. Already lost part of it's slipper and is severely cracked.

Taken both heads off, had the two valves replaced and now looking to get all necessary gaskets & some head bolts as I had to drill out a few stubborn ones.

I'll post a full report once it's all back in.