Dear Jag brothers,

I finally did the passenger side of my jag's secondary timing chain tensioner change with the ziptie method. Much thanks to EZDRIVER who guided all of us with a genius idea.

Here is my video on youtube:

I will be doing the driver side very soon. Been really busy at work lately and get tired when I get home.

question and suggestion are welcome. We are all here to learn and share with each other.

 

How did you replace the primary tensioners?
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So far just the secondary, I will leave it like that. I dont have time to do the whole job right now.

 

Keep a sharp ear out when starting the car. You might be able to catch it before the engine destroys itself.

Some people can hear a rattle at start up but sometimes you don't.
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tbird, that noise you mentioned with start up is for the primaries? wonder how long they last

 

I have found that the primary timing chain tensioner blades and chain guides can become broken or cracked with age causing the chain to rattle. If you did not replace the primary chains and associated parts with the secondary chains and tensioners, you are really on borrowed time.

 

tbird,
I have a question regarding the primaries.

1) If I do decide to change the primary tensioners and guides, without the chains, can I do them without removing the valve covers and special tools besides the crank pulley remover? i think if i unbolt the front two bolts of valve cover I can take the front cover off after removing all bolts holding it?

2) I don't understand why chains have to be replaced and why are these guides prone to failure. Most cars have plastic guides but didn't quite understand why jags are more prone to breakage.

 

Replacing the primary chains and associated parts requires removal of the front timing cover and the use of the special tools to remove the crankshaft pulley and hold the crankshaft from moving. The camshafts must be correctly timed using the tools and the VVT units set up correctly with the new chains.

Use the search function to find threads with photos of the procedures for replacing the primary and secondary chains.

The 4.0 Litre version of the AJ-V8 engine had several shortcomings from a design standpoint, which were corrected in the later 4.2 and 5.0 Litre engines. When replacing the secondary tensioners, use the latest version along with new chain guides and tensioner blades for maximum life. There are several members of this forum with 4.0 Litre engines that have exceeded two hundred thousand miles.

 

Well you are right about the plastic and we generally call them plastic tensioners but even the third generation metal tensioners have plastic in them too.

So it's a matter of degree because all tensioners have some plastic in them.

You can read why Jaguar had all the problems and it comes down to DOHC engines put massive harmonics into the cam drive system. Many DOHC engines use timing belts to help cushion this. We have chains which are much longer lasting but do not absorb shock loads as a rubber belt does.

These harmonics are caused by the unequal loading on the cams from the valves and lobes as they rotate. You can really see this yourself if you ever remove the cam chains. It's hard to turn the cam and then it will jump and be easy to turn. Multiply this hard/soft loading by the RPM of the engine. We are beating the tensioners to death!

For the 4.2L Jaguar not only used the improved 3rd generation metal tensioners but they also upgraded the chains too. This is why you don't see tensioner problems at all on the 4.2L and 5.0L.

Now I have heard of one guy who did have tensioner problems on a SC 5.0L but it is still very rare. Can't get anything except the dealer told him that. So not very strong evidence.
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Tbird,

So that is the reason the secondary tensioners are under a lot of stress but generally the primary tensioners and guides should last as much as any other care with timing chains right? most guides are made of plastic in almost any car with timing chain. Why are primaries still a concern her on this forum. It seems to me that the secondaries need attention asap rather than primary.

 

It's hard to say and I have to follow what Jaguar did to solve the problem.

They upgraded the primary and secondary tensioners as well as the chain. That's a lot of improvement and I don't think any car company would spend the money if they could get by with less.

Remember also that we are now on the third revision of the tensioners so I think they did try to make just the minimum changes needed but found out the problem was worse than originally thought.

Plus numerous people have replaced the secondary tensioners and they were battered and beaten if not in pieces.

Here is one that was run too long!

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wow that one looks horrible. Do you know if they did make any changes to the primary tensioners and guides? I am worried about my car now but I a have been hearing the the primaries give you a warning generally but I am assuming secondaries are more prone to stress due to the fact they open and close valves at a higher speeds and with enormous pressure.

 

That is a good detailed question and I don't know.

Lets hope Abonano jumps in here because he has done the repair himself (and it's no small job!) and is pushing 230K miles on 4.0L which has got to be a record or close to it.

Paging Abonano!!
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The most critical part of the job when replacing the primary and secondary timing chains is making sure the VVT unit on the inlet cams is correctly positioned when installing both new primary chains.

Due to the compact design of the S-Type engine bay, the air conditioning compressor, power steering pump, alternator and all the brackets for those items must be removed to gain access to the timing cover on the front of the engine. There are also several special tools required to correctly do the work and ensure there is no damage to the flex plate and harmonic balancer.

JTIS Workshop Manual also provides guidance as well as the torque values for reassembly.