806 Common Rail Diesel Leak problems - HELP!!!

Right, I`m at my wits ends with this car - 1999 Peugeot 806 TDI!! I
have now had the pipe from the pump to the rail tighten that many
times, each time being told by the garage that it won`t leak again but
it does!! The last time it was "fixed" was about 2 months ago, 4 prior
to that and about the same before that. Each time, the leak occurs at
the common rail end (as opposed to the pump end) and have had a new
pipe fitted twice. The pipe has been put on properly (by a diesel
specialist!) and tightened correctly!! I really don`t see an end to
this unless it`s welded on at that end!! Why should it suddendly start
leakinf after x number of months. There`s no real excess amount of
vibration. Is there ant type of diesel "locking" thread compound or
similar? I appreciate there`s a lot of pressure in these pumps and
wondered if this is a commom problem in these cars.I really don`t
think the leak`s from the common rail itself as it "appears" to be
leaking at the union with the pipe. HELP PLEASE!!!

 

Sounds like the sealing ring at the end of the pipe is giving the
problem,may be there is some one out there that has had this problem
and got it sorted a easy way. and not put it in to a garage and get
charged pounds and pounds, for just a small job,

 

I do not think this is a common problem. My 1999 406 HDI has done 124,000
miles and never leaked and I have two friends with HDIs who likewise have
had no problems. I do have a recollection of a recall early on to do with
a possibility of a diesel leak but cannot be sure whether that was the 406
or my previous car which was a non turbo 405. A recall is likely to apply
to all HDIs I would have thought, so it might be worth checking if there was
one for this problem and, if so, whether yours was ever done.

Other than that, Chris's suggestion sounds good or is there a possibility of
a hairline crack?