Try using a Nissan oil filter next oil change. Some of the aftermarket
oil filters don't have an anti-drainback valve appropriate for Nissans.
That valve prevents oil from completely draining back to the pan when
the car's sitting overnight. This will cause the funny noise when
starting up.

CD

OK, thanks.  The noise does occur everytime the engine is started, hot
or cold no difference though the sound may abruptly end a tad sooner if
the engine is hot.  I don't yet have a Factory Service Manual for this
Sentra so I'm guessing on this one.  My 1987 Sentra has a belt which
I've changed multiple times.  Thanks again.  Al

I wouldn't get too excited about it...

Thanks for the helpful comments.  The car has 99,000 miles on it.  I've
just noticed the sound but I've only owned the car a few weeks.  It
appears to happen just for a second or two when starting the car when
cold.  I will make a point of determining if it occurs when the engine
is hot.  It sounds like a mild scraping sound.  It certainly would be
consistent with a hydraulic tensioner just before getting oil pressure.
It end abruptly as the engine starts.

Am I correct that there should be no such noise whatsover if the
tensioner is operating correctly?  Thanks again to all.

  Al

*usually* you won't hear a chain going bad, (unless you have links
that snapped, which is highly unlikely), more often the tensioners
wear out and you get slop in the chain which, eventually can make
the chain jump a tooth and throw your timing off.

I guess the slop could be bad enough that you could hear the chain
slopping around but that would be *after* the engine warms up, not
just when it's cold.

Can you describe more about the sound?  Any idea from what part
of the engine it's coming from?  Does it happen when you start the
engine after it's been driven?  Does it happen all of the time?  Have
you opened the hood and listened while someone else started the
car?

I just bought a 1999 1.6L Sentra.  Runs great, engine smooth and quiet.
I do occasionaly hear a slight metallic sound for a second or two
during start-up on a cold engine.  Can anyone describe the
symptoms/sounds associated with a timing chain going bad?  Thanks.