The issue or worry of chain noise and potential failure has come up on several threads, even on other cars that have the same engine like RR/LR. And there seems to be no unified opinion. Many of these are engines with only 30,000 miles. Some have had it serviced for $3K, others have done it under warranty, some say to ignore it. Regardless there seems to be no specificity as to the cause. Also there is a TB on the RR 5.0 for this thing- which btw is the exact same engine. Weird.

I reached out to one of the top technical minds in the country on modern engine design- one of my closest friends. Described the problem, chain noise during first 10 seconds of startup. He said easy- hydraulic tensioner. Wait it gets better. So I look it up in the training guide and Jaguar specifies that they use hydraulic tensioner and that they are doing something special to PROLONG chain life!!

QUESTION: Are they intentionally lowering tension during startup? The training manual also states that the oil pressure at idle is 2bar, compared to 6 bar at 1500rpm.

BTW- the Training Guide is the best piece of literature I have read to date on the 5.0 engine. It answers hundreds of questions that I see folks arguing blindly about on forums. Such as 'what does the reading on the electronic dipstick mean' 'how is it measuring is it compensating for incline- why the 10 minute wait- all explained.
http://www.jagrepair.com/images/Trai...%204-15-09.pdf

Thank you in advance

 

From post 15 in this thread : 5.0l cam chain tensioner problem - Page 2

 

Yes the question is- is this by design, i.e to keep the chain loose during startup. The problem is quite prevalent one of our members just turned down a purchase fearing further expenses.

Notably the chain rattle occurs only during initial 5 to 10 seconds, even when you simply restart a already warm engine.

Now, what is this technology they are speaking of that prolongs chain life; is it removing tension during startup? Which makes some sense.

Incidentally guys at the RR forums have done the service only to find the problem prevails.

Again there seem to be a lot of grey matter around this issue, at least officially.

 

I have heard the startup ticking noise on my XK with 49k miles. It seems to have quieted down after the last oil change. I also have a Subaru, so I am a bit deaf to chain/injector/heat shield noise.

As far as the "extended life" stuff, from the manual you posted : "Timing chain with oil pressure-controlled hydraulic tensioners avoids requirement for costly belt replacement" just means a chain last longer than a belt.

 

Around 25,000 miles my XKR started having a startup chatter. Ended up being a bad hydraulic Chain Tensioner. About 28,000 miles the car would start fine but then a Tick would set in. Ended up being one of the 4 actuators. 3 times the engine got dropped. Also the hydraulic chain tensioners failed again (twice). Eventually in the last year I got a brand new timing chain, 4 brand new actuators, and the entire hydraulic tensioners replaced again. It sounds perfect now. Alot of the BAD NOISES these jags make come from this chain, its tensioners, and as I found out the actuators. I was told there was an update to the timing chain used and the tensioners used about the 2013 model year. My XKRS got the new equipment based off VIN number, my XKR got the new equipment after the original failed. I kept sound bites for everything if anyone wants to hear what the startup chatter sounds like (bad hydraulic timing chain tensioner) or the engine ticking (bad actuator).

Loth

 

SeanU, Thanks a bunch mate. I really appreciate you pointing out that it was bit of clever marketing speak.

 

Yes please mate! you dont hold stuff like this back.

 

Loth,
What service shop did you use- it might pay to have my car sent there. there is no substitute for competency.

 

Service shop was Byers Imports in Columbus, OH. What is your email and I will send clips off my computer later tonight.

Loth

 

The timing chain was changed to a different brand sometime between the 2012 model year in the US and the 2013 model year in the US. Apperently the 5.0 engine does a great job at eating the chain and causing problems. It was best they do so after having so many awful noises to have my chain, chain guides/tensioners, and all 4 actuators replaced at the same time after the previous attempt. Thats alot of changing to moving/noisy parts and it is no wonder now with all that changed out that my Jag sounds BRAND NEW up front. I also had the supercharger problem with it eating itself in the last year that was completely replaced as well..... engine dropped 3 times, taken apart 4... hopefully I can get her to 100,000 miles from 30,000 miles clean and dandy

Loth

 

Yeah, that's me you're quoting. I don't claim to have any 'inside knowledge' of the tensioner issues. However, I know from the manuals that the 5.0 hydraulic tensioner uses a ratchet mechanism to maintain a level of tension (probably not full tension) when there's no oil pressure, specifically in order to avoid rattle on startup. I'm pretty sure that Lothar's problem was just a busted ratchet, so that one of his timing chains was under-tensioned and rattled until the oil got through to it.

But if the tensioner is always loose on startup, I can imagine that there's additional chain wear and the possibility of the chain jumping, particularly as it will naturally stretch over time and the slackness will increase (which is why we have tensioners). And that will cause serious engine fornication.

 

Cheers,
You have simmered it down. The ratchet mechanism is whats failing if its sole purpose is to provide tension till the oil pressure comes up. Precisely why the noise is going away.

Apparently its not a question of if it will fail, its when. Loads have had the same trouble and may not listen as carefully. Hard to do when the problem only last a very short time when the engine is at its loudest.

I dont know if the ratchet device can cause total meltdown. I found it incredible that the bloke from the other forum was able to drive a car 150degs out of time, and he said it ran fine. Did not make sense.

 

Well, when the tensioners failed on the 4.0 engine, it was a complete failure - they were spring-based, not hydraulic, so the chain would lose all tension regardless of RPM. At that point, if the chain was a bit stretched, it could come adrift - and then the cam stops and valves meet pistons.

With the hydraulic tensioners, if the ratchet fails you're only exposed at relatively low revs during startup - obviously it's possible that the whole tensioner might be failing on some engines, but I haven't seen that reported. Most people have just noticed a rattle on startup that then goes away, which is a bit disturbing but less of a worry than if the rattle carries on. While it's not ideal, I think it's considerably less likely to lead to engine damage than the 4.0 tensioner failures.

 

All of this makes me so glad that my XK has the trouble-free 4.2 litre engine, which is plenty fast, smooth and makes all the right noises and none of the bad ones. I have to agree that the issue with the 5 litre engine is not nearly as serious as the tensioner problem in the old 4 litre V8.

 

I would say the jury is still out until I see the data on how many fails there are. As we all know these form usually bring out discussions on reliability because some of the users experience them. We on the other hand are a small percentage of owners so I would like to see the data on any of these issues. As an example I asked the service manager last time I was in on how many 5.0L waterpumps were replaced at their dealership. He said he only remembered 2.

 

And all engines have their weak spots, it's just some have more/worse than others. The valley pipe on the 4.2 being an example, so it's not entirely immune. The 4.0 was a particular lemon in original form, with the Nikasil bore coating and too much use of plastic components that weren't sufficiently thermo-stable in the long term (tensioner bodies and water-pump impeller, to name the worst offenders). The 4.2 is just a development from that, with most of the bugs squashed. What is impressive about the 5.0 is how few issues there have been, considering it was a completely new design like the 4.0 was.

 

Timing chain at 50k was common sense maintenance on most hi-perf cars. On Maserati you could set your calendar by the fact that it was going to slip at 40k and miraculously it was a full interference engine, valves and pistons was their biggest selling item. The upshot to the 5.0 JLR engine far outweighs the niggles. I would be pissed if that was a repair on a less exciting engine. In fact, its the desire to keep it in top form that lead to this inquiry. I actually love the high-tech aspect of the AJ133, it makes the ownership feel that of a true supercar.

Enzo Ferrari used to say that you buy the engine and we throw in the car. I feel the same way about the XKR, except its a much better car that Jaguar throws in.

 

Does anyone have a diagram of the said Ratchet device. Or even the whole tensioner.
It behoves us to see what the issue might be. It would be brilliant if we could find a way to take the uncertainty of failure out of it.

did anyone keep their old one?

 

This is what the tensioner looks like:



The sequence shows how to lock the piston down using a 'grenade pin' prior to installation. I assume the ratchet is internal.

 

The picture tells a good story to me. See if I have got this wrong: the procedure for depressing the piston is making sure its fully extended first- which must make the catching clip (ratchet) fall off. Then the clip catches again once the piston starts extending. If its gummed-up its not going to catch properly. It cant be a wear problem that you would get with a spring-loaded ratchet mechanism. Nor can it be a problem of the disengage side of things not working.

Which really makes a good case for using lubricants that wont cake up- I have posted a video many moons ago how the Jaguar castrol oil is infinitely superior in this regard. Also makes a good case for de-gumming the engine- with techron or similar. Any thoughts on this part?

Also somewhat explained is that Jaguar could have avoided the startup slack problem by simply decreasing the lower limit of the piston. But they did not, they went an extra mile, so why? Food for discussion.