Wow, I'm amazed there are so many people suffering the same as me. I'm going to check the hoses this afternoon and keep my fingers crossed its nothing more serious or expensive.
Thanks very much you all, your help and advice is GREATLY APPRECIATED.
ANDY
11th Apr 2013 9:03 am
stav
Member Since: 14 Nov 2013
Location: Athens
Posts: 178
Hi Andy, did you find out what was generating the noise?????
28th Nov 2013 12:10 pm
crwoody
Member Since: 09 Mar 2009
Location: Littleborough
Posts: 2109
Funnily enough I was about to ask a question on a new thread about the exact same subject, then I found this one
My D3 had been doing the same as described here for some time, most noticeable when coming off the throttle and sounds just like excess boost pressure being released.
There's no noticeable loss of performance that I'm aware of, unless of course I'm just used to it, and it doesn't appear to have got any worse since I first noticed it, this led be to assume it wasn't something like a split hose which I would assume would get worse over time with increased deterioration.
The big intercooler to inlet manifold hose is new, having split a few months ago, but the comments here have now got me wondering about the other two smaller ones after the turbo, I guess I'll have to go and check unless someone has a better plan ?Clive
28th Nov 2013 12:57 pm
stav
Member Since: 14 Nov 2013
Location: Athens
Posts: 178
Crwoody, can the sound be heard while coming on and off the throttle while in neutral???
Mine does it only when on D (autobox) and the car is moving. Not when stationary, hence its difficult to diagnose
28th Nov 2013 1:13 pm
fishinmad
Member Since: 30 Jan 2012
Location: St Ives
Posts: 877
My car also makes this noise when coming off the throttle to and has done scince new (96K now), other D3's in my area make the same noise so I thought it was just something they did!Club Narpy Torch
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28th Nov 2013 1:59 pm
crwoody
Member Since: 09 Mar 2009
Location: Littleborough
Posts: 2109
stav wrote:
Crwoody, can the sound be heard while coming on and off the throttle while in neutral???
Mine does it only when on D (autobox) and the car is moving. Not when stationary, hence its difficult to diagnose
No, like yours, it's only audible when moving, usually going uphill when the turbo is actually producing some boost, blipping the throttle while stationary wont produce the effect.
I was hoping that by now, someone might have come along to say "there's a boost over-pressure relief valve", never mind, I live in hope Clive
28th Nov 2013 3:54 pm
stav
Member Since: 14 Nov 2013
Location: Athens
Posts: 178
Went to the most respected dealer in Greece today, had a ride with him, windows open, just to ask what on earth is this sound!!!!!
The reply was: "Its the EGR" , he also said that since mines are blanked i shouldn;t worry about it at all!!!!!!!!!! When i asked why other cars dont produce this sound, he said that my EGRs should be very dirty, and even if they are blanked they still work, producing the sound.
I have no reason to argue about what ive heard, and the reason is that this is the first mechanic giving a straightforward answer rightaway, without scratching his head
28th Nov 2013 4:37 pm
wizbongre
Member Since: 26 Oct 2013
Location: Liverpool
Posts: 691
crwoody wrote:
I was hoping that by now, someone might have come along to say "there's a boost over-pressure relief valve", never mind, I live in hope
Wouldn't that be the wastegate on the turbo? I assume D3 turbos do indeed have a wastegate?
I've just had my turbo refurbished (or fixed, or replaced, or left alone, depending on what mood the garage is in and how hard they want to try and explain what they've done!) and it now makes this slight whoosh noise as you get on the power and off, or at very low revs and light throttle. To me it sounds like the wastegate working to keep the boost up and stop the turbo stalling when at relatively low engine revs. I've heard lots of turbo diesels (and indeed earlier turbo petrol engines) make a similar noise and I'm sure my Audi A8 does it too but thanks to the half tonne of double glazing and sound proofing, I can't hear it like I can on the Disco!
29th Nov 2013 2:25 pm
Gareth Site Moderator
Member Since: 07 Dec 2004
Location: Bramhall
Posts: 26748
I am pretty sure that the turbo on a diesel engine does not have a dump or blow off valve. The reason is that on a petrol engine, the speed/power is controlled by a 'throttle' in the inlet manifold that 'throttles' the air rushing into the engine when you release the accelerator pedal, and a turbo petrol engine needs the dump or blow off to stop the inlet pipes downstream of the turbocharger exploding, because the pressurised air would have nowhere to go.
On a diesel engine, there is no 'throttle' as such (ok there is a butterfly valve in the inlet, but that only shuts when egrs are open). When you press or release the accelerator pedal, it increases or decreases the fuel supply to the engine. The diesel engine runs with the inlet tract fully open all the time, so no need to dump pressure when the pedal is released.
I think the noise you are hearing is either the air rushing through the pipes/intercooler (or a split/hole in either) or the turbo vanes spooling down.
No, like yours, it's only audible when moving, usually going uphill when the turbo is actually producing some boost, blipping the throttle while stationary wont produce the effect.
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29th Nov 2013 2:44 pm
wizbongre
Member Since: 26 Oct 2013
Location: Liverpool
Posts: 691
Gareth wrote:
I am pretty sure that the turbo on a diesel engine does not have a dump or blow off valve.
Maybe not a dump valve but do they have waste gate's on the turbos? These usually work to control the maximum boost the turbo can achieve by reducing the back pressure, allowing them to spool up and then when they reach maximum boost (say 1bar or whatever it is) modulating to maintain that pressure otherwise the boost would continue to rise.
That's my understanding of petrol engines at least and just assumed it would be similar for diesels although as you point out, with no throttle plate as such in the induction flow I'm now re-thinking my logic!
I'm off to google turbo design on diesel engines...
29th Nov 2013 3:26 pm
wizbongre
Member Since: 26 Oct 2013
Location: Liverpool
Posts: 691
Found an explanation already...
The variable technology in the turbo essentially acts as the wastegate, varying the pressure it can generate however diesel engines don't need to limit the boost and actually, the more boost the better.
So in short, I don't have a clue what I'm talking about and I need to go back to the drawing board as to why my car is whooshing...
29th Nov 2013 3:32 pm
Gareth Site Moderator
Member Since: 07 Dec 2004
Location: Bramhall
Posts: 26748
No wastegate on diesel turbo either as far as I know. The boost pressure is regulated electronically by the variable vanes, which alter the amount of exhaust gas entering the turbine stage.
I think wastegates and dumps are old technology now?
29th Nov 2013 3:32 pm
wizbongre
Member Since: 26 Oct 2013
Location: Liverpool
Posts: 691
Yeah, think that sums it up.
To be fair, I was basing my knowledge on my Nissan Pulsar GTi-R which was built in the late 80's so not exactly cutting edge!
Is the whooshing noise coming from cars with auto's? And does the noise come from the near side?
If so, it is probably the plastic bracket that keeps the gearbox oil return/flow pipe away from the turbo pipework. Or its the turbo heat shields rattling slightly. Same sort of area.Mark.
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