HDI rattling heard when accelerating

[charentejohn]

Any ideas, I have searched generally and found possible problems from old injectors, noisy cat converter to disintegrating cam pulleys, so.........

I know diesels can rattle when under load but what generally causes this. I have worked on cars a lot in th past but all petrol, diesels only recently.

When cold I hear a rattle in the cabin, not terrible but there, when accelerating in the gears, reduces as the engine heats up but still audible. Also reduced in higher gears and almost gone in 5th.
What is the most likely cause of this, car has 115k miles, no smoke from exhaust, runs well otherwise. On tickover and revving when standing still no problem, just under load I think.

The engine mounts need replacing (bottom one especially as 'softening') so could be normal noise just transmitted to cabin due to this ? Could it be the gearbox or just old injectors ?
A common diesel problem but why do they do it ?

[DickieG]

What age is your HDi? Citroen issued a software update to reduce this noise, my present HDi had the first version of software and suffered from excessive noise when accelerating until I updated the ECU.

HDi's do make more noise than a TD when accelerating but how much more is obviously subjective and requires another similar car to compare noise levels as being excessive.

[RichardW]

And....

Check the crank pulley, these fall apart, and the first sign is rattling, especially when cold.
If the noise is quite distinct, and then suddenly stops when you get to a particular rpm (might be 3,200) it is a worn injector - instead of helping to reduce pre-ignition, they dribble a bit, and cause more pre-ingnition! The ECU cuts this at 3200 rpm, and the noise switches off

[charentejohn]

The car is a 2001 Xantia with 115k miles.
Are there signs of a pulley failing (apart from noise) so I can judge if it needs doing, no small job I imagine. I saw a photo of one of these that broke and it didn't look good.

I do have the lower engine shield removed, as still working on oil changes. I didn't think it was worth replacing till I am finished and still looking for Total BV oil, not easy here as no car parts shops as such.
Is it possible this is allowing noise to 'drift' under the car ? I know from soundproofing other vehicles most sound enters through floors not bulkheads.

Not high rpm related but I rarely get over 3000rpm, steady driver, but will give it a go. I have this on an old transit but not as much, and kind of expected due to lack of sound insulation and age.
If I don't accelerate quickly, by backing off the throttle to slow accelerate, I can control it but it is still just audible.

Edited to add that I gave it a run today and hit near 3000rpm in 3rd gear and cold (not my usual) and it quietened down at this rpm. Still a little noisy when cold but quieter when hot now. I wonder (hope it's not pulley) if the injectors are clearing ? Just added fuel cleaner and done 120 ish miles since then, so may have cleared a bit. If so I will run to 3000ish again a few times.

Normal revs for max. noise are between 1700 and 2200rpm. I checked how I drive today and 2500rpm is my normal max running at or below 2000 normally, mow boring am I ?

[KevMayer]

Is the noise like a pinking sound?

[charentejohn]

Yes, if it was petrol it would be just like pinking but a little lower pitch. Not so much tick as tock, if you see what I mean...

If just injectors then I can deal with that in time but if something might go bang then best done asap. I assume pulley noise would be due to a fracture opening and closing, but would it be visible or not ? I guess the problem is that with the timing belt under tension it is impossible to check the pulley. Sort of catch 22.

Could it be gearbox ? doesn't sound likely but reduces as gears get higher, only just audible in 5th and accelerating from 2000rpm. But then so does load in higher gears so may be reduced load on the engine that is the reason for any decrease in noise.

I don't think this is critical, unless 80% chance it is the pulley, just something I will get rid of if I can.

[RichardW]

The pulley in question is the one on the outside that drives the Auxiliary belt - it is a rubber sandwich job, and the outer lets go of the middle. If you have a look at the pulley and it is covered in rusty dust, or there are even shards of metal coming off, then that is a good sign it's shot. Otherwise paint a couple of radial lines across it and see if they slip relative to one another. If it's the injector problem, it has a very distinctive shut off as the revs rise, easy to diagnose.

[Peter.N.]

If its an injector causing the noise it will only do it while the throttle is open - take your foot off and it will stop.

Peter

[charentejohn]

I am hoping it is just an injector as it does reduce to the point where I have to strain to hear it when lifting off the throttle, cruising it goes away. That said as ever I will remain paranoid and keep listening and experimenting to confirm this.
I have a sneaky feeling that as it was run without a thermostat for some time, now fitted, and I don't rev it much an 'Italian tuneup' may help. Also the Forte cleaner I added may dissolve some of the big lumps on the nozzles I will wait until the rest of the fuel, 1/2 tank to go, has run through and see how it is.

Good to hear it is the outer pulley only, I can live with that and would consider changing it next belt change anyway if it is a potential problem. I was planning to carry a spare auxilliary belt in case it ever breaks, as i understand the car is then dead in the water until done, and will also carry a spare pulley too. I will paint a stripe as suggested anyway just to be sure.
In France it can take days to get parts if you are taken to a.n.other garage for repairs, so if I carry the parts I can just have them fitted by the recovery company if away from my home area.

[DickieG]

I can't help thinking that the injector noise you describe is perfectly normal, direct injection diesel engines do produce a rattle when power is applied due to additional fuel being injected and are noisier when cold due to lower thermal efficiency in the combustion process. I'd be far more concerned about the bottom pulley falling apart because if that happens it'll more than likely cause the auxiliary belt to get caught in the timing belt followed by the tinkle of bent valves,,,,,,,,,,,

[KevMayer]

Some time ago I blanked off my EGR pipe where it connected to the inlet manifold.

WIth it blanked off I noticed the engine making a loud rattleling noise under acceleration, just like a pinking noise.

There was a lot of discussion about EGR on here at the time and Cachaciero provided a lot of information. In a description of the benefits of EGR, on the Wynns website, one thing is that the return of cooled exhaust gas reduces the combustion temperature to stop pre ignition. So, if the EGR isn't working one effect you'll notice is pinking under acceleration.

When I unblanked my EGR pipe I noticed that the pinking noise went away.

So, your problem maybe that your EGR isn't working.

[DickieG]

I've disconnected the EGR on both of my HDi's I can't say it's made any difference to the running apart from stopping the EGR valve and manifold getting gunked up with crud.

[CitroJim]

There was a lot of discussion about EGR on here at the time and Cachaciero provided a lot of information. In a description of the benefits of EGR, on the Wynns website, one thing is that the return of cooled exhaust gas reduces the combustion temperature to stop pre ignition. So, if the EGR isn't working one effect you'll notice is pinking under acceleration.

I belive that's not 100% true Kev. EGR is there for no other reason but to reduce NOX emissions by lowering the combustion temperature to below that where NOX species are formed.

That it was associated with 'pinking' (which diesels do anyway as part of their combustion process) was purely incidental I would think.

[DickieG]

I've just read the Wynns article but I'm not sure it's as simple as they describe, IIRC the EGR valve is only open under light engine loads or idle so in this instance pinking under load won't really apply, the other thing to bear in mind is that less oxygen due to the engine ingesting exhaust gases = poorer combustion/consumption.

Unless I find out more I'll leave the EGR disconnected on my two diesels, better that than the hassle of cleaning out gunk.

[CitroJim]

I've just read the Wynns article too..

This paragraph:

If the EGR valve sticks closed at higher engine speeds, the combustion
temperature will become too hot causing knocking or pinking; this sounds like
rattling ball bearings in a tin and is the result of fuel burning at the wrong time
(before the piston has reached the top of it's compression stroke). This kind of
detonation is very harmful to the engine. Prolonged periods of pinking will
shorten engine life or worse cause the engine failure.

Is complete and utter bollocks when applied to a diesel engine There is no way that pre-ignition can happen in a diesel. Until fuel in injected there can be no ignition, pre or otherwise.

Modern diesels (HDi included) use pilot injection at low revs to start the main combustion off gently and thus reduce the old familiar diesel knock.

Rather than suffering pre-ignition, all diesels exhibit a condition known as ignition delay where a finite time elapses between injection and the onset of combustion. Diesel has a fairly low flash point. Above this temperature diesel will spontaneously combust and it's ability to combust will not be changed by being in a very hot combustion chamber; if the temperature is above flash point then diesel will go bang. That's a fundamental principle of a compression ignition engine...

I can only suggest Mr. Wynns goes back to diesel school and dons the dunce's cap for a while.

From the point of view of a petrol engine then yes, his argument does stand up a little but do modern petrols have EGR? PSA engines never did but do they nowadays?

If a modern diesel sounds like a bag of nails or is distinctly knocking than there will be a fault elseware. Dribbly injectors are a prime candidate...