Tapping noise from engine on cold start
 

Haven't run the S8 for a few weeks, started it today; fired up almost instantly despite a weak battery. Clear tapping noise from the engine heard all round the car outside though inaudible in the drivers seat.
Stayed for ages while I let it idle - checking/adjusting tyre pressures. Went for a short drive and it had gone on return.

Listening carefully it seemed to be at half the RPM frequency. So idling around 800-900rpm (13-15/sec) it was about 7 taps per second.

Any thoughts on what it is, how to narrow down the source and how significant it is?

I don't know these engines at all yet.
But that sounds like a hydraulic lifter sticking.
Sure someone will be along soon with a more robust solution /reason.
Kind regards

You raised this back in 2018, and MJ responded in post #6:

https://forum.a8parts.co.uk/showpost...97&postcount=6

Any other search result is generally about the startup rattle.

:ROFL: Well remembered, Sean. At my age you forget these things!

The engine has been in MJs expert hands since then so I thought I'd better ask anyway.

My old Rover 800s (I had almost as many of them as IT had S8s!) were very prone to this so I recognise the sound. :o

More like the benefits of Google. I just noticed that donp38 had beaten me to it.

I fired mine up this week after several months and had the exact same noise. I let it idle for a bit and it got quieter but didn’t completely go away. Once I went for a spin around the block it was pretty much gone. That was on Thursday. I fired her up again today and there was no noticeable noise +++