406 V6 clunk or knock mystery

When I start to accelerate, either from a standstill or after
deceleration, there is a quiet, but obvious soft single 'clunk' or
knock from the suspension or possibly drive gear. It can repeat as the
gear box changes down during lower speed braking. It doesn't appear to
be an engine noise. It never varies in loudness or number of 'clunks',
always one, and always at initial acceleration (whether gentle or
otherwise) as well as when I take my foot off the gas. I am wondering
if it could be a suspension/engine mount or a drive gear issue. The
performance of the car is not affected. It's not loud enough for
passengers to say 'what's that?'
Anyone experienced this? Any ideas?

 

This is possibly way off but when the Cat on mine split at the front end
a few weeks back, what you describe is exactly how I would describe my
experience. It was jarring one way or the other with the sudden change
in engine speed. It eventually fell right off. I bunny-hopped around a
car park to have a friend diagnose the problem as the clunk was the only
thing I was sure about - the increased noise the problem caused I tend
to think is in my head.

 

I have a v6 and have had the same problem - or very similar. On seeing
your post I jacked up my vehicle - the whole exhaust sytem seems to be
firmly intact. Nothing seems about to fall off.

So the mystery remains - assuming my and Anvil's problems are the same.
But it was nice to have a possibility to check out.

The vehicel was in for service a few days ago and I did not mention the
problem but it is still present.

 

You're probably lucky its not that - it wasn't cheap to fix at that end.
Still half as cheap as Kwik Fit originally quoted me, although once
they'd had their poke around it only took another 4 miles or so to fall
off so its not like they did nothing for me...

 

One of the engine mounts often goes on the V6 406 - I can't remember which
one though ! It's fairly cheap and easy to replace. I seem to remember the
break can be pretty hard to spot !

 

Thanks guys/girls (must not assume anything...)
When I had the deaf mechanic from the dealership listen for the
'clunk', he did mention that they could book the car in to check the
engine mounts. That's exactly what it sounds like - the noise caused by
a rocking motion , subtle and consistent. The service manager naturally
couldn't hear a thing....... Interesting to read the other replies.
Since my car is under warranty, I'll get it looked at and let you know
what is found.