Hmmm - restricting tensioner movement just limits how much slack it is able to compensate for, so I don't think that's a good concept. I don't know what the ratchet failure mode is, whether it sticks or breaks, so I can't speculate on how to avoid it.

I'm still not convinced that a brief rattle on startup represents a significant threat to engine longevity. As I said earlier, full-blown tensioner failure leaves the chain loose permanently at all revs, getting worse as the chain heats up & expands, and that really is a problem.

 

Lots of new information has surfaced that may make you reconsider.

Apparently its a massive problem across the board. No manufacturer- even those known for ultra-reliability has been spared. Ford, Toyota and Hyundai even, anyone that uses a hydraulic tensioner, and lots do. The problem seems to be 2-fold as Ngarara described, faulty ratchet and stretched chain. Particularly in DI because the chain also does the donkey work of driving the high-pressure injector pumps.

Lets get something out of the way- can it jump timing- absolutely. Watch this guy demonstrate.

Now watch this video, its the exact problem I have heard on several Jags.

here is a great article about the whole matter, which tells us a lot as to why and what.
AGCO Automotive Repair Service - Baton Rouge, LA - Detailed Auto Topics - Timing Chain Problems II

I say 50,000 -60,000 miles- change chain, insurance policy if nothing else.

 

This article is particularly illuminating.

In addition, specific timing chain tensioner designs can present issues.
According to one manufacturer, the timing chain tensioner is the heart of the timing system just as the oil pump is for an engine. Often overlooked, if proper tension isn’t maintained the system will prematurely fail.
Slack in the chain will cause it to ride up on the sprocket teeth and stretch or break the chain. Timing systems using hydraulic chain tensioners are operated by using engine oil and oil pressure.
Variable valve timing is the state of the art, according to industry experts, but even this new technology will be surpassed in the aftermarket. How turbocharging, direct-injection and other future technologies impact ever-smaller timing components will be the next challenge.

One other note for hydraulic tensioners used in the late-model timing systems. Using the correct OE design oil filter with “check valve” along with recommended oil viscosity has become critical on these systems. If there’s a delay in oil pressure on initial startup the system will not have the correct amount of tension on the chain causing it to ride up on the sprocket teeth. The chains have become so long on overhead cam engines that the system will not tolerate slack in the chain(s) for very long without damaging the system.
Installers often don’t realize how these operate and are affected by the overall condition of the engine. It’s critical that the engine is operated using the correct type of oil and oil viscosity.
Oil changes must be done when recommended by the OE manufacturer to keep a clean oil supply. The tensioners have very small oil passages and check valves that can become plugged, reducing the amount of pin pressure being applied to the tensioner arm or chain.
When a timing system fails and it uses hydraulic tensioners, other areas of the engine must be checked before installing new timing components. The overall condition of the engine has to be good. A worn engine will have problems with oil pressure whether cold or hot / idle or while driving and could have sludge and dirt built up inside it. A low oil level can introduce air into the oiling system and cause problems with these tensioners resulting in an intermittent pounding effect on the chain instead of constant steady pressure.
Because clogging of these tensioners and VVT solenoids is such a dangerous threat, some OE manufacturers have started putting internal check valves along with oil screens inside of the tensioners and solenoids to extend life. Others are using what’s called a ratchet design that holds tension on the tensioner pin maintaining tension on the chain when the engine isn’t running.
Engine startup after sitting overnight and cold ambient temperatures can cause a delay in what manufacturers call tensioner “pump up” and can cause a sudden pounding effect on the timing chain causing abnormal wear on the tensioner arms and guides. The arms and guides are normally made of plastic or have a plastic liner for the chain to ride on with an aluminum back/carrier.
The bottom line, experts say, is that you must use the correct type of oil and viscosity. Remind your installer customer to tell their customers that regular oil changes must be done to maintain a clean oil supply.

 

This is what we call a classic 'Runaway" i.e. Slack begets slack which begets new engine.

 

Hmmm, OK, thinking further: the ratchet not only maintains tension at startup when there's no oil pressure, it also maintains tension if the hydraulic element isn't working properly. So, a busted ratchet probably won't cause any harm by itself, but it does present a significant risk if there's a second failure within the tensioner.

Therefore, if you get the startup chatter, it would be a good idea to get the tensioner replaced. And when you do that, may as well replace the chains & guides too, since much of the effort is already expended in just getting to the tensioners.

 

I agree, all 3 things should be changed. The wear on the chain is the real culprit on all these cars. I found the SECRET in a patent that GM filled. They have apparently found a solution they claim, a pressure relief valve, whats important is them acknowledging excessive chain wear with ordinary hydraulic tensioners.

Can this be done without removing the engine, how many hours does the book call for.

 

Here is the patent approved.

Patent US6609987 - Hydraulic timing chain tensioner assembly - Google Patents

 

I have found a way to check the timing belt and make sure it does not have engine destroying slack.

Could some of you also verify.

The timing chain is visible by removing the oil filler cap. I was able to push up against it to see if there was any deflection. (btw, also a place to lube the chain should you be starting it after a month of storage and the chain was bone dry)

I was most impressed to find that the chain had oil on it despite not being run for a week and really thin oil viscosity. Which typically runs down to the pan as fast as it can.

 

Don't know about the hours, but the engine stays in.

 

I brought this subject up over a year ago & it was not taken seriously. The timing chain issue has been a known issue on the 5.0 engine for over 3 years. The original fix was to disassemble the front of the engine & replace the chains & tensioners. The later fix was to replace the tensioners with an updated version. This repair under warranty paid about 12 hours. We had a couple of cars that the chains were so stretched that with new tensioners fitted still made noise. This meant taking it apart again & install new chains as well. The issue was more common with Range Rover as there are far more of them on the road with the 5.0 compared to the Jaguars. The water pump issue was so common we were doing 3-4 a week. It is also a know issue with the 5.0. We would have cars towed in with the intake manifold melted because they had gotten so hot.

 

Wow! Those are seriously engine killing issues. Has there been any recalls issued for either problem on any models of any MY year for these problems?

 

Its a UNIVERSAL issue and not isolated to Jaguar. Every manufacturer has had to deal with it. Big problem with Honda- the highest quality manufacturer.

Because Jaguar has very few cars out there the problem is not well known. There is nothing that Jaguar is doing nothing unconventional.

HOWEVER, it is a bigger problem in Jaguar than Honda because their engine is not worth saving nor expensive and has much less load on the chain than Jaguar.

Noteworthy: GM and Honda have scrambled to come up with improvements to the hydraulic tensioner problem. And because they have taken totally different paths, it tells us that they havent found the problem. GM thinks there is too much force on the chain that leads it to wear, Honda thinks the ratchet mechanism is the culprit.

Below is the only article we ever need to read on the issue
Honda K Series Tensioner - The Truth Behind The Failure - Honda Tuning Magazine

 

I have no question in doubting your observations but without the data from LR & Jaguar it is difficult to determine how significant either one of these and other issues exist. No manufacture wants to own up to having design flaws resulting in expensive repairs so I suspect that is the reasons we don't see TSB or recalls for these problems. Also no manufacture unless it involves law suits wants to release any data of said issues. So I guess we'll have to hope and wait and see if our own cars fall into these problems. It would be nice to get a recall but I won't hold my breath.

 

But its is not a flaw if every single manufacturer has had the problem.
Most importantly no one has solved it. And opinion seems divided, some say the stress put on a chain by DI fuel pumps- you will get chain stretch, no 2 ways about it. The answer seems to be to Invent a new type of chain that has less wear potential.

I deal with this in my work a lot, we call it stackup tolerance. Each link has a 1/1000th of an inch wear. Insignificant. But if the chain has 1000 links, its now larger by a full inch.

 

There may be some legal recourse against Jaguar, they have erroneously trained their techs to believe the chain requires less replacement than a belt. Not true on this car.

BTW here is a tip to get a little more life out of the chain. Turn the silly auto air off. It engages the aircon compressor clutch even in cold weather to rejuvenate the seals. You can do so manually once the car warms up and the chain has more tension on it. Why lug the engine anymore than necessary.

 

If you go back to the first he tells you there is a TSB on this issue. It is a Rover bulletin that came out over 3 years ago. As he states it is the same engine.

 

OK can someone post the TSB and if it were a problem with LR then why wouldn't we see one for Jaguar. Just asking.

 

Subscribed.

 

I don't think they felt the need. Remember the company is Jaguar Land Rover. It is all the same company just different models, same engine.

 

The air-con compressors on the XK are clutchless. Turning off the air-con or putting it in to Econ mode just sets the compressor current to its lowest limit which puts the compressor solenoid valve in the minimum flow position. It does still cycles the compressor though.