VVT / timing chain problems
 

Hi all

I recently had my car checked out by a mechanic I've used a couple of times (not Jag specific, just a local) due to a horrid rattle that sounds like metal being whacked repeatedly on metal for approx 1 second at a rate of about 12 hits in that second - so a real loud RATTLE coming from the engine area.

It only happens when the car is being started after being off for a while (say over 40 mins), if the car was to be turned off after a drive and started again in 5 minutes, you wouldn't hear this rattle.

He came to a couple of conclusions without dismantling the whole thing and costing me an arm and a leg - perhaps something to do with VVT/solenoid or the timing chains + tensioners... Now I am not particular savvy when it gets this mechanical - I just drive the bloody thing and try to take care of it.

He suggested that it wasn't damaging my car/engine in anyway but that eventually it might mean that the only solution would be replacing the whole lot... we're talking thousands of ££.

Has anybody experienced something like this before and can input any wise opinions on what it might be / what I should do?

EDIT: It sounds JUST like this in terms of speed/length of the rattle but far louder and sounds a lot more like metal on metal rather than plastic on metal:
Many thanks
Hayden

I have my own theory, tell me if I'm being an idiot...

does the chain tensioner use spring or hydraulic pressure in the 2007 4.2 XKR?

If hydraulic... could it be that the oil is not filling into the hydraulics quick enough on a cold start and therefore the chain is rattling? However it doesn't happen when the car has been recently used because the oil hasn't drained yet?? Or am I talking our of my arse? I really don't know...

I very recently had the oil flushed out and replaced + a new oil filter and if anything, the rattle was actually slightly more aggressive afterwards and now lasts about 1.5 seconds from cold startup instead of the previous 1 second.

I am curious, do you know if the Oil weight was changed from your previous Oil? Spec used to be 5w-20, but I hear now(not sure how long ago) Jaguar is using 0w-20.

Thanks,

Dave

He used Castrol 5w-30! Just noticed this. But this is what Jaguar recommend? Not 5w-20?

Not absolutely sure about the 4.2, but on my 5.0L it says 5W-20 on oil cap and in manual. But, I am hearing from multiple sources (including Castrol) that Jags new Oil Spec for all is 0w-20 and only Castrol Edge Professional E 0w-20, vs the prior oil recommend being Castrol Professional OE 5w-20

This could all be Jag trying to shed the previous Ford spec WSS-M2C925-A and replacing it with their own proprietary Jaguar spec STJLR.51.5122

In other words they make it very confusing.

Sorry to add to that, LOL

Cheers,

Dave

That's for the 5 litre as the tolerances are much tighter requiring a lower 0W viscosity. For the 4.2, 5W-30 should be fine depending on climate.

Hayden, change your oil filter and go through the x150 service manual looking for a check valve in the oil system. Sounds like you check valve is letting the oil in the passages bleed back into the pan. And yes, the chain tension is oil pressure maintained.

Thank you, will do that.

The timing chain tensioners are hydraulic, but they also have a ratchet mechanism to ensure that the chain is taut on startup before there's sufficient pressure to pump up the piston. The oil pushes the piston out, and the ratchet stops it from returning when the pressure drops. If the ratchet fails, the chain will be slack until the pressure pushes the tensioner into place.

Lothar had this issue on his XKR (5.0, but the tensioners are similar), and it had a nasty rattle on cold start.

I had this problem on my 4.2 XJ for many years. The general conclusion is that its caused by some pin in the VVT system getting stuck (or unstuck) and thus creating a ruckus until sufficient oil pressure has built up. Supposedly it has no negative effects on the engine. My car made that racket for several years and several tens of thousands of miles with no ill effects. I never got it fixed because the operation would've been too big and expensive, as it would require removing the timing cover. I can tell you it was sometimes quite embarrassing starting the car if people were nearby.

I tried all sorts of different filters and oil weights and nothing worked. I wasted a lot of time and money.

Supposedly one of its causes is too-long oil change intervals. I've never gone more than 3-5k miles between oil changes ever since, no matter what anyone says.

Do you think it will hugely effect resell price if I eventually decide to sell the car? OR just slightly?

It's certainly going to 'disturb' a prospective buyer - you can explain what it is, but I suspect it will create a nagging doubt. I would certainly think twice about buying a car with a mechanical issue, even if I was told it wasn't serious - I'd certainly want the price to reflect the fact that I might have to spend money to fix it. But I'm more likely to walk away and buy a car that doesn't have an obvious problem.

Hi all,

Just resurrecting this old thread as I have a 2007 XKR with 96,000km on the clock and is exhibiting the same symptoms now, as that described by Hayden. Loud timing chain rattle on start up that only lasts for 1 to 2 secs.
Have done multiple oil and filter changes, but to no avail.

Any definitive thoughts as to the cause of the problem and recommended fix?

Cheers;

Remove the cam covers and inspect the secondary timing chain tensioners for cracks or broken nylon inserts. I have seen broken secondary chain tensioners on the AJ33/34.

If there is slack in the primary chain(s), the primary tensioners have most likely failed.

I gather that this is a very rare if not unheard of occurance in these later 4.2L cars. So the only way to get to the root of the problem is to undertake major exploratory surgery then? And if the primary tensioner shave failed, would they not rattle consistently?

Cheers;

While uncommon, it does happen with the AJ33/AJ34. With the cam covers removed, use a borescope to inspect the primary tensioners and guides via the timing case.

If there is wear to the components, the rattling may become more consistent, even when the engine is warm.

Are there specific mileages/times when the timing chain's tension should be examined / adjusted / parts changed?

Anyone? :confused:

I always heard the 4.2 was bullet proof according to this forum or at least the people that own these cars. Guess not. Timing chain issues still a problem on all Ford/Jaguar product. Google Ford eco boost timing chain VVT adjuster stretch/ rattle on start up and you will see the problem has been going on for more than a decade. You can see Ford can’t design a cam timing system with DI that actually works for more than 60k miles . Problem is still not fixed and made worst by the clowns that insist no need to use Ford / Jag approved oils and change oil once per year.

If the engine oil is changed frequently and the oil meets Jaguar specification, then the engine should function normally. Bear in mind that while the AJ33/34 and the AJ133 are well designed, there is always the possibility that failures can occur. These failures are not unique to Jaguar designed or Ford engines.