Ive been very careful with oil changes but recently
The 2010 XK has started intermittent timing chain rattle
on startup on the US drivers side of the engine.
im aware of the tensioner issues ( slow return of tensioner )
as well as the guide button wearing.

the other day at a stop light the car started running rough
and misfiring, restricted performance came on the display
and I had pending misfire in the drivers side bank for
cylinders 2, 4, and 8. After about 30 seconds and a few shifts
It went away and all was back to normal..

Did my engine jump timing intermittently??!

anyone with timing chain experience please chime in.

I really dont have the funds to do a chain and tensioner job.
hoping I can clean the tensioner with additive and change the oil.

The rattle on startup is quiet and intermittent.
The codes dissappeared shortly after.
No CEL 69k miles

 

I've done the chain/tensioner job on the 4L, not on the 5L yet but the basics are the same. If it skips a tooth forward, then I cannot imagine any way that it could skip a tooth back. The engine only ever turns one way. I believe you'd have a consistent/persistent error (if not a complete failure) once a chain has skipped.

 

The timing chain definitely cannot slip back once it has gone over but I suspect that your timing chain is the problem.

It could be getting so loose due to the button wear that it is almost jumping a tooth sufficiently to trigger a warning but not enough to actually push the chain over the top of the teeth. I think that you need to either get the chain looked at or stop driving the car as there is no simple "fix" possible. If you continue to use the car it is virtually inevitable that it will permanently slip and that could well then damage the pistons and valves requiring a far bigger expenditure. As it is, it's not a difficult job as the heads will not need to come off.

Richard

 

Thank you for the replies.

I'm changing my valve cover gasket soon so I will check the chain by hand
and see if it is loose when I get the valve covers off. I will snap some pics too
and update this thread.

 

UPDATE: When I did the passenger side valve cover I checked the chain for slack and there was very very little movement
for example if you try to move it, it will not make any noise just slightly flex.
Today I checked in the oil cap for the drivers side chain with a screwdriver and my hand for any looseness or noise,
and same deal no noise or rattle.

Is there anything else that would cause a very metallic high frequency/pitched rattle on cold start that follows the engine speed
and goes away shortly after? I will try record it next time but it really sounds almost exactly like the spokes of a bicycle while
coasting but less consistant.

 

Just to confirm, the tensioner problem is with the primary (lower) chain tensioner not the secondary (upper) chain. I'm not sure that you can properly check the primary chain unless you remove the front cover.

Richard

 

Maybe you really hear the supercharger isolator making noise? They are a known wear part and not a horribly expensive repair.

 

Cee Jay, I don't have an XKR, i wish!

My understanding is the tensioners are driven by oil pressure through a tiny hole on the side
of the tensioners. If this hole becomes blocked with sludge, (its pencil tip sized) the tensioners
will not push on the guides to keep the chain taught.

I'm going to do a oil flush with Liqui Moli engine flush before I change my oil and see if it goes away.
the noise is intermittent at this point.

 

Going off the pic looks like there is only the one chain per head unlike the 4.0/4.2/4.3 & 4.7 which have the upper and lower chains or am I missing something ??

 

Ah, could be. I thought the configuration was basically the same as my 4.2.

Richard

 

Correct, one chain per head.

is there lower tensioners?

 

Hi pressure fuel pump(s)?

This is what my '10 XKR sounds like from cold. Once the revs drop you can hear the noise from the pumps pulsing in and out.


This is what is sounds like once warm:


I can hear the noise from within the car if I drive it from cold with the windows up and it goes away after a minute or two.

 

Thank you for posting the videos, unfortunately this is not the sound i'm hearing.
As the revs drop it sounds more random like rattling and as it idles it goes away.
almost like small nails

 

As promised, I checked my timing chain tension from the top of the engine
while I did the valve cover gasket on the drivers side. I'm not sure if this is
an accurate way to mention chain tension.

could anyone chime in if my chain tension looks acceptable or problematic?

Thank you

Oddly enough my 2010 XK chain looks more robust then
the ones in other videos...

 

Heres a video of a loose chain that may have
skipped a tooth, but this doesnt give reference to the
status of the tensioner..

 

That looks OK to me so perhaps the start-up rattle is something else or it might be the other bank, I suppose. The only way to be sure would be to remove the other cover although I would be surprised if one chain was so much worse than the other.

Richard

 

Ive changed the cover on the other side and the timing chain is the same, so I might be hearing things..

 

JLR changed the chain design later on so yes there’s a difference.

 

I suspect the earlier design was better..

 

Someone in here posted comparison pictures, but I don't remember who did it.
I do believe the 'new' one is wider but wimpier. The old one was narrower but way beefy. IF I remember correctly.