I've had my 98 4l XK8 for about 1 year. I have a trip over the Alps into SoF in a few weeks, so I thought I'd better check if the secondary tensioners were type 3's as the car always sounds tappity on start up, followed by a noise like a zip fastener closing, then quiet as a ***** should be. Checked the left bank, half the screws in the rocker cover snapped, but I wont go into that. Left adjuster is all aluminium and secondary chain is tight as should be, so I removed all snapped bits of thread and replaced with new.
The right bank, only one of the centre bolts snapped which was an easy fix with a 3mm drill and a Torx bit gently persuaded into the snapped bit by Mr hammer. Got a nice type 3 tensioner here too, except it's not tensioning the secondary chain which is a loose as a loose thing. Is it worth removing this tensioner and soaking it in kero, see if it's gummed up, or is it a replacement job? The thing has no visible wear on the face at all.

 

I'd replace it if it was mine.

 

Unless the installer forgot to pull the release pin it's bad. My understanding is that there is a ratcheting cam in the tensioner that locks it against the chain when the engine is shut off. There have been a couple of reports of failure.

 

I've ordered a new one from British Parts UK. I'm very surprised to see this go. I was told by previous owner that the all ali tensioners were fitted, but it sounded so much like death rattle, I thought I'd better check, rocker cover gaskets were leaking oil and bolts were snapped, so my faith in the 'Independent Jaguar specialist' who'd regularly serviced it was low. (It really was a known Jaguar specialist too! All stamps in the book) I think I may qualify for the 'Dodged a bullet' club

 

Some advice would be appreciated. I've reassembled the left rocker cover, as explained, the right hand secondary chain seemed alarmingly loose. I turned the motor clockwise to line up the cam lobes before starting to change the tensioner, the chain tensions up straight away. I expect some slack when turning it counter clockwise allowing for clearance between teeth and rollers, but this chain becomes quite loose when you turn the crank back just a touch. Should the tensioner be holding the chain tight regardless of the direction you turn the crank or is it normal for it to slacken off so? I'm concerned now because I only tried the left bank in an as it was state (didn't try turning crank anti clockwise) as I was only in to check what tensioners were fitted and to cure oil leaks.

 

The type 3 should not allow a lot of slack, but turning ccw will loosen chain. There is a warning in the manual about turning ccw may damage the bearings, but I'm not sure how serious it really is for a small movement.

 

I only took the pressure of drive off, in much the same way as the pressure of the cam lobes and valve springs would at certain points when you shut down. I'm surprised at the amount of chain slack above the tensioner this procedure produced. I don't think it's right, I would say something in the tensioner has failed but wonder if any other experienced mechanics/owners can advise. With a small anti-clockwise movement, it's possible to lift the secondary chain right out of the grooves in the tensioner top heel.

 

The tensioner was fine, I replaced it with the new one anyway as I was in there. There is no ratchet in the tensioner, just a light spring and oil pressure, so probably normal for it to go slack when not under tension (turned anti clockwise) One tip I would pass on; I read other peoples experiences when doing right hand bank secondary tensioners with zip ties, many experienced problems lifting out the camshaft. Very important point; turn the crankshaft clockwise to line up the two flat machining's on the front of the cams (as if you would be using the lock down tools) then loosen the cam bearing caps nearest the chain first, easing back the bolts on all the caps leaving the furthest two from the chain until last loosen these last four evenly whilst gently lifting the chain end to keep the pressure even. This prevents the castings adjacent the bearing on the first cap next to the cog from becoming stuck (they are a clearance fit and must not be lifted at an angle) This may not make immediate sense but if you follow this tip, there is almost zero risk of snapping the camshaft.
My efforts were in vain as the engine still makes the same noise as before, a faint tapping until you raise the revs a little, then a zipping noise followed by quiet. I'm going to try a comprehensive oil flush followed by an oil change, if that doesn't help, I might remove the VVT modules, see if they are sticking as it's been suggested that these may also cause a rattle on start up. Any other thoughts would be appreciated. I didn't go into the timing chest to check the guides and main adjusters, but what I could see looked good and there was no slack in the chains so I'm sort of comfortable with that. Many of the rocker cover bolts snapped as previous 'specialist' must have been a little heavy handed, but I found pulling out the spacers from the cover gave good clearance to drill into the studs with a 3mm drill, just enough to hammer in a small Torx, then you could easily undo them as they are not under stress. (leaving the cover on prevents swarf getting inside the engine, a small magnet removes it before you take the cover off. Hope some of this advice helps others.

 

Nope, no ratcheting cam in the tensioner, just a light spring and oil pressure.

 

I think the thick rubber gasket on the valve (and other covers) somehow gives a false sense of tightness (or lack thereof) when you don't use a torque wrench. I haven't snapped any bolts on the valve cover, but have snapped a couple on the timing chain cover at the front of the motor. I feel your pain !

 

Following a post about VVT rattles, I found a youtube video of a guy operating the VVT solenoid with a 12v battery remotely. That's exactly the noise my right bank makes, followed by that exact same ratcheting noise when he manually operates the VVT solenoid. I'm going to do an engine flush (something I normally loath) My motor is quite gummy with orange/red oil deposit over much of the internals (I think it had a head gasket go once) so the VVT may be gummed up a bit. If the oil flush doesn't help, I'm going to ignore the rattle now I know what it is, I can tackle the VVT's next year when I change the cam chains.

 

It's a real gut wrenching moment of despair! At least they aren't seized in the head though. I think if the previous clown hadn't so over-tightened them, they wouldn't normally become seized in.