Identify the Noise - win.. nothing.

Heres a bit of fun amidst my Sunday afternoon anguish at possibly not
having a car to commute to work in next week.

Take a listen to this clip and see if you can tell me whats wrong with
my car (2.0 HDI Engine - Pug 306 '99)

This morning, whilst cold and idle, it developed a rattling/tapping
sound. It is clearly there throughout the clip but most prominant just
after I lift off after revving.

http://homepages.which.net/~derek.hawley/carnoise.wav

(yes I know, shame I couldn't MP3 it, encoders seem to dislike short wav
files)

Help appreciated.

Cheers,
Tom.

 

Timing a notch out

 

Oh. Does this mean piston/valve damage?.. What can cause this to shift?
Worn cambelt? I was coming up to replacing it within the next 5-6k
miles. If no damage, would I be right in thinking that this would be a
good course of action to rectify the problem as a whole?

 

If that was the problem, it wouldn't.

 

If as in "he's wrong" or if as in "its ridiculous to assume thats the
problem based on a 20 second audio clip"? I'm not assuming anything,
merely trying to work out what the problem is.

Still, comforting to know that i'm not (yet) looking at an engine
rebuild, so thanks.

 

No, as in if the timing is a tooth out, you'll not have the pistons
hitting the valves. For that to occur, we're talking 50+ degrees out,
not a handful which a notch out would be.

What he is referring to, I think, is the pump timing being out. The
pump is run off the belt/chain and you can think of it along the lines
of ye olden distributor on petrol engines but with diesel instead of a
spark. It has to be set to inject the diesel at exactly the right time.
If it's a bit out you get a knocking sound. Likewise in a petrol car,
if the ignition timing is out, you can get pinking.

If it is out, it means the timing belt has stretched or slipped (unless
it had been doing it since the last belt change) - neither of which is
a good thing.

 

What he is referring to, I think, is the pump timing being out. The

And for anyone googling for the exact definition of pinking, please ignore
any of Peter Macmillan's posts.

 

To the untrained ear it sounds like every other diesel on the road

 

It's hard to say.
It's more like something just affecting just the one cylinder.
If it had been worse when you revved it, I would of said a leaking exhaust
manifold gasket, but I'd hazard a guess at something wrong with either a
tappet or injector (the tapping seems to match the engine speed quite
closely).

Can you tell what area the tapping is coming from?


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To the untrained ear it sounds like every other diesel on the road

True, if I hadn't known what the car normally sounds like i'd probably
assume it was normal ... but like I suspect many others, I am very
sensitive to any change in the sound of the engine. I drive a lot more
care-free when music is drowning it out, quite frankly.

 

it is a common rail, look up the essentials on that and correct your
answer....

 

Its really hard to tell. If I had to describe it i'd say its internal.
Its a lot more noticable from inside the car or aside the car when the
bonnet's closed. The noise of the vibration with the bonnet open drowns
it out.

Seems to be coming from the head.

 

As it's an HDI then the pump timing can not be out. The pump basically
just pressurises the diesel into the coomon rail and then to the
injectors, which are electrically opened when required. Which is why
when the belt is changed you don't need to time the pump.
What it sounds like to me, and as you say it is difficult on a short
WAV file, is the crank pulley starting to rattle. A friend of mine had
the same thing and he was convinced it was an injector, but when I
heard it, especially first thing in the morning with the A/C on, I
could hear it was coming low down from the pulley area. Shine a light
down there and I could see metal filings on the undertray and wing
trim. It was by this time pretty noisy.
Anyway, have a look at your pulley. It is quite a common fault on
HDI's.

 

This morning, whilst cold and idle, it developed a rattling/tapping sound.

Sound quality is good. I have similar engine in a Citroen Xantia. Must admit
that's what it sounds like on cold and frosty mornings.
Any difference when hot? Does it run ok?
DaveK.

 

What it sounds like to me, and as you say it is difficult on a short

Hmm. Sounds pretty catastrophic. I'm nowhere near experienced enough to
even get down to the pulley let alone diagnose whether its the cause of
the problem, but reading around the subject this is the most fitting so
far. What causes this wear on the pulley?

 

On the very cold mornings it has extremely loud diesel rattle but thats
perfectly normal and it generally quietens down once the temperature
approaches normal. I didn't actually run the engine for long enough
today to reach normal running temperature, so not sure, but it felt, to
drive, absolutely normal.

 

Also sounds exactly like my Xantia until warmed up as well, and it's just
had a service including cam belt change.

 

You don't have to "get down to the pulley". Just look down from above
with a good light and see if there are any meatl filings yet. There is
a rubber bonding in the pulley and it becomes unbonded and the metal
parts rub together and make the rattling noise and the filings. They
cost around £120 (Citroen part) or £160 (Peugeot part). I have heard
you can get a solid pulley to fit from Peugeot for around £50, but I
have never followed this up. Takes no more than an hour to fit.

 

If the Pug 306 '99 is equipped with a knock sensor, then I would
not feel easy until I have shown to my satisfaction that the tapping
noise is not of rapid engine knocking. The 7 year old car could have
enough accumulated carbon deposits to cause this detonation.
Before last weekend, the knock sensor was able to produce adequate
retardation of the normal ignition advance to eliminate the detonation.

While there are other causes of the abrupt appearance of the noise and
of the close correlation between frequency/loudness and throttle pressure,
a faulty knock sensor can be easily tested and eliminated.

 

Ignore my last post! Just read the update!