V6 clatter

[xantia_v6]

the v6 has hydraulic tappets, it is not unusual for one to lose some oil while the engine sits with a valve open, but normally it will refill and quieter down after running a few seconds. I have heard one that was permanently noisy, and suspect that it would require a replacement tappet, which is a cam-out job.

[addo]

Good tappets are not cheap. You can sometimes get used ones refaced by cam grinders; make sure they determine if the surface treatment will sustain a light grinding.

[CitroJim]

Mike, does the rattle cease after a few seconds of running?

You quite often hear a rattle from the tappets immediately after starting a very hot engine when it's idling very slowly. One blip of the throttle sees the engine quieten down...

If the noise is constant and does not go in a few seconds, I'd have a look at the cambelt rollers and tensioner as a first port of call just for peace of mind.

Can you identify if the noise is just coming from one bank. A stethoscope should be able to pinpoint fairly closely the guilty party if the noise is confined to the front bank. The rear bank is a little harder...