Lower timing chain rattle.

[Kes]

Like a large percentage of jaguar owners, I'm fed up with timing chain rattle. I had the top chain checked by the garage which they say is fine so i can only guess that it's the bottom chain that's making the noise. Is it possible to adjust/replace this without removing the whole engine?
Hope so.
K

[christopher storey]

Yes but it is a major job requiring the head off, the front pulleys etc off , so as to remove the lower front cover. It does surprise me that you say "like a large percentage of Jaguar owners" because in fact lower chain problems are pretty rare, slackness in the top chain being much more common, and a lot of suspected chain noises are in fact tappet noises

[Kes]

That's interesting! Is there a way that I can differentiate between tappet and timing chain noise? I'm only going by the remarks from my local garage so you may well be right. The noise comes on after a few seconds of starting the engine and it's louder at certain revs - and as the revs are decreasing if you blip the throttle. It's definitely a loud 'tap' rather than a 'knock' but it does spoil the lovely sound of the straight six and it's the one thing I notice when I drive other peoples etypes.
Thanks for your advice.

[PeterCrespin]

That's interesting! Is there a way that I can differentiate between tappet and timing chain noise? I'm only going by the remarks from my local garage so you may well be right. The noise comes on after a few seconds of starting the engine and it's louder at certain revs - and as the revs are decreasing if you blip the throttle. It's definitely a loud 'tap' rather than a 'knock' but it does spoil the lovely sound of the straight six and it's the one thing I notice when I drive other peoples etypes.
Thanks for your advice.

I agree with Christopher. Invest in a mechanic's stethoscope - cheap ones are fine, and you'll soon track it down. If there's a lower chain problem it may be either poor rebuild technique or a worn hydraulic tensioner. Eventually the chains need replacing but they last into 6 figure mileages.

Pete

[ALAN COCHRANE]

#2 for a mechanic's stethoscope. I had similar tappety noises and rattles with my 3.8. The rattle turned out to be the upper timing chain which was too loose and the tappety noise was due to incorrect valve clearances. Both sorted and the engine really does now purr like a big cat.
Your timing chain should be one notch back from "dead tight" to avoid any chance of a rattle. The tappety noise can easily be checked and localised with the stethoscope and then a good set of feeler gauges.

Alan

[KingRichard]

Your timing chain should be one notch back from "dead tight" to avoid any chance of a rattle.
Alan

Hi,

You mean one notch on the micro-adjusting plate?. I thought that flexing the chain with a screwdriver and have 1 cm flex is OK.

Richard

[ALAN COCHRANE]

Richard

I found that with that much play my chain rattled especially after the engine fully warmed up. Setting the chain "dead tight" and backing off one or two notches on the eccentric tensioner introduced the required amount of slack without risk of rattling. Unfortunately the manual only states "not dead tight" which isn't the most scientific measure in the world.
I also found that investing in the proper eccentric tensioner tool for the princely sum of ?15, was money very well spent. I had read that long nose pliers would suffice but couldn't take up enough slack using them. The tensioner tool made it a doddle.

Alan