Please see attached photo which shows the upper passenger side tensioner which appears to be completely missing the orange nylon parts. The bottom tensioner's nylon is intact, but has cracks. The very top of the chain looks to have been micro polished, but not deforemed or abraded away from contact with the top tensioner now exposed metal.

I was getting a light metal rattling sound from this area which persisted after removing the super charger belt and serpentine belt, so I pulled the valve cover and had a look at the primary tensioners. I upgraded the secondary tensioners when I bought the car last summer.

My question is how I should proceed.

My thoughts are to do things in this order:

Drop the lower oil pan and look for chunks of the missing orange nylon guides for absolute and obvious confirmation.

Then order the primary tensioners (can anyone tell me a good source for these?)
Then remove the front clip, radiator/fans, then the required accessories, then timing cover.

If the chains look as good as they do in the photo, my plan is to only change the tensioners themselves and thereby not risk messing up the timing, making this a much safer operation. The car only has 56K miles and has always had synthetic oils changed at least every 5K miles.

Can anyone give me advice if this is how you think I should proceed?

 

Your picture shows the chain guide, not a tensioner. I would replace the guides and tensioners, but I've never heard of trying to do it with the chains still on. What state are the upper tensioners in?

 

Ah, yes, the upper is a guide, and not a "tensioner" since it is not applying any tension. My mistake in vocabulary.
I replaced the upper tensioners last summer when I bought this car.

Can you confirm that you think the nylon/plastic portion appears to be missing?

Also, can you recommend a good source for the guides and lower tensioners?

 

It looks similar to mine, with cracks and bits missing. I just went and looked at my pictures, and I'd say you probably cannot get the guides out without removing the chains, since there is a lip on the back side. See here-

Actually, the more I look at my pictures, the more I think it may work.



I bought my parts from Christophers Foreign car Parts.

 

In this shot, the RH bank has a ton of slack, since the primary tensioner had failed. So if you unbolt the actual tensioners first, you should have lots of slack to then unbolt the guides.

I don't know if you've ever done headgaskets on yours, but you must know the XJR is famous for blowing those. So be forewarned, you may to do all this work again to pull the heads.

 

"you may to do all this work again to pull the heads"<---- I've got my fingers in my ears and am saying "LA LA LA LA LA I CAN"T HEAR YOU!!L AAALAALLAAA"

That, and I'm now running a solid 18 and sometimes 19 lbs of boost!

 

My buddy Buck had a great idea!

Instead of dropping the oil pan, I could just look at the filter, something is bound to be in there.

This is only a 10 minute job...

 

On second thought, all the chunks could very well be larger than the screen before the oil pump, so I might as well drop the oil pan anyways since i'll want to remove all the pieces.

Having had a look under the car, I am pleased to see there is no cross member or anything under the pan, so it appears to be very easy and straightforward.

 

you could use a borescope through the drainplug hole

 

That was too simple and good an idea for me to think of it.

 

Here's my advice- you obviously drive the car hard, so just cut to the chase and replace the lower guides and tensioners. You'll have peace of mind then.

 

Agreed.
I ordered the parts & gasket sets from Christophers this morning.

 

Update,

I took off the oil pan and found nothing but a perfectly clean oil pan with zero particles and the screen to the oil pump was also without a single particle.

Worthy of note, I noticed that if I stand on the brakes and press the gas some, the volume of the noise goes to almost nothing.

Also worthy of note, this noise only begins after the car has been running 5 minutes.

I'm a little confused as to what the problem is. I have ordered the parts to swap the primary tensioners and will swap them out when they arrive in 1 week.

I'm guessing there are large pieces of tensioner material that are too large to make it down to the lower pan.

Either way I think it would be wise at this point to open her up and have a better look. Even if there is something else going on, I would feel better knowing the primaries have been changed. The rest of the car is too close to showroom condition.

 

1st vs 3rd gen primary tensioners.

 

So I pulled off the lower crank pulley reasonably easily with the help of a $12.99 pulley puller from harbor freight.

The upper passenger tensioner guide rail was cracked, but it was not missing any pieces. It appears that the entire rail is covered in nylon. See pic of new vs old. There is some wear on it but no pieces are missing. The other 3 rails looked almost new. This car has had top quality synthetic oils since day 2, and has lived in a temp controlled garage until I bought it. Quite the garage queen as they say. I was surprised at how good the other rails looked.

I suspect that the tensioner itself has failed as it was not applying any tension to the lower tensioner rail. I will be replacing it with a new one.

 

The tensioner that has no piston showing has failed. There is a check valve in that that traps the oil and tensions the chain. Exactly what I had in mine.

 

Thank you for that info.

3 of the 4 rails looked very new with very little wear. This car has always had top of the line synthetic oils since new, and only has 56K miles on it now.

I changed just the rail that was cracked and showing moderate to major wear and changed both primary tensioners. I'm guessing the noise was the chain slapping the upper passenger side rail and cracked it while doing so. Hopefully after it is back up and running that noise does not come back.

Given, the other rails were in almost new condition, and it took me less than two hours to take everything apart the first time, I thought it best to not "fix" what was not more than say 30% worn. If I need to do this again, I know it is not that much hassle to get the front timing chain cover off again.

 

Didn't you order all the guide rails?

 

I did, but only one looked more than 20-30% worn...

And the tensioner side had the nylon protruding out the side, so the head of the bolt gets lost down there and the ratchet had nothing left to grab on to, so I put the original, almost new one back on.

Did yours do this, or did yours come with a washer or different bolt?... mine did not come with bolts.

see pic

 

Go here,( to reply #71) and see how the rails fit. I used all the original bolts. You are nuts not to replace all the guides while you are in there.
https://www.jaguarforums.com/forum/x...r-97146/page4/

Look at reply 74 while you're there, in fact, read up on all the various threads on tensioner replacements, there's lots of good info out there.