Intermittent tappet sound at idle speed?? - Jag V8 4.0 1998

[W5Plumbers]

This sound comes and goes with a blip of the throttle, can anyone advise on how this happens and any way to treat?

Thanks

[Orcadian]

Difficult to diagnose without a bit more info, can you post a sound clip or short video with sound?
Noise from front end of engine? Top end, left bank, right bank?
Any history of chain tensioners having been changed for later type?
Running well on all 8 or injector noise?

Ian

[W5Plumbers]

Hi Ian and thanks for the reply, I can take a video clip when back after the break but in the mean time I can tell you the engine runs perfect, does not miss a beat hot or cold with a silent start up and zero noise chains ( so can only assume that tensioners have not yet split if they are the early type) the noise emanates from the top end left bank, I would say but really need to get a rod to it and to my ear to be 100% from which cylinder, its definitely not injector noise. As mentioned it comes and goes (slowly creeps in after getting warm then cleared with a blip of the throttle) miles are 100k now but years ago I had the same problem on a jag V8 with only 27k miles but sold it so never got to investigate further. Could it be a hydraulic tappet??

Thanks
Aaron

[Orcadian]

Hi Aaron,
No hydraulic tappets to worry about, the AJV8 unit has bucket and shim adjustment. When you say it goes after a blip of the throttle, is that a sharp stab or a prolonged increase in revs before letting it idle again? Best to let more ph folk hear it when you get chance.

Ian

[Jaguar steve]

At 100k with the symptoms you describe it's potentially secondary timing chain rattle or on a n/a 4.0 a VVT unit loosing oil pressure. When was the oil last changed?

Either way I'd get a diagnosis quickly