Disco 1 Turbo sounds like a police siren and it won't go away please help!!

Hi all, this is a bit of a long post so apols in advance but I have a whistling turbo problem that's absolutely doing my head in, it's not too been too kind on my bank balance either so any help would be greatly appreciated!

So the story goes, fairly recently purchased a 1998 300tdi auto Jap import, drove a faultless 800 mile round trip to Switzerland and was all going well until last month. We were heading to wales and about halfway into the journey (75 mph on the motorway) the turbo starts whistling like a police siren whenever it was on boost.
Couldn't do much while I was away so got back and started to investigate. Turns out the air filter had torn apart and it clearly sucked something in as when I got the manifold off, one of the turbo fins was bent, so I decided a new turbo was the least she needed.

While it was apart I decided to do the following.....

Full recon turbo including manifold and horns,
New alloy intercooler, the old one was corroded pretty badly,
Cleaned the inlet manifold,
All new studs, gaskets, and stainless nuts etc,
EGR removal which was a PITA as the Jap ones have the water-cooled EGR valve,
Silicone turbo hoses with all new clips etc,
Full service, all filters oils etc,
Checked and cleaned all the main air hoses (all good as far as I can see)
and for good measure worked out some of the electrical gremlins it had with the dash lights etc

So I torqued up the last bolt earlier, primed the turbo crossed my fingers and gave her a whirl, she cracked into life and sounded sweet so feeling all proud up the road I go..... gently for a mile or so, let it all warm-up and then... yep as soon as the boost hits the same flaming whistling sound is still there. I want back rechecked and made sure everything was tight and seated properly (again) but its made no difference at all,

It's definitely not just the turbo spooling and not the uj's or drive train etc, I've been over all that stuff and it was definitely not there for the first 3000 miles I did in the disco, It only ever happens when it boosts under load and if I drive it keeping the revs low I don't get the siren. I'm going to get new intake hoses just in case, but following that, I'm at a bit of a loss so if anyone out there has any ideas it would be a massive help!

Cheers in advance, Tim.

Hoses split or leaking would be the obvious area if everything else is good.
The numpties with sporty hatchbacks try to make their turbos noisier by improving the air intakes with after market filters and shorter hoses so if your intake is holed or split somewhere it could be the source.
Can you reproduce when not under load, free reving?
Just wondering if exhaust side!
Is there any power loss or even gain?

This is kinda where I'm heading although I did check everything, and double check and check again!

It doesn't do it when just revving only when boosting under load and believe me I've tried to recreate endless times. I guess it could be exhaust related although on inspection that also looks good and it does sound like the siren hails from the passenger/airbox side.

One thing about the intake mine seems to have a MAF sensor or such like?? But I've seen loads of 300's without this. Is this a Jap import thing or a year/variation thing? I also removed cleaned, refitted said MAF with no improvement!

Your Jap market re-import will have EDC - is this all present and correct, and is it doing its self tests correctly? Any fault codes ?

removing your EGR valve will make it fail the MOT - So .......

It's probably, as already mentioned a burst hose .... does it do it if you do a TQ stall test ? - if so, then try the test with the bonnet open and see if you can identify the location .... take decent safety precautions !! Although it is "only" 1 bar pressure - it can throw things at you - possibly into your eyes = not good.....

No no fault codes and not too worried about the MOT I have all the bits so can put it back for the test.

What would the TQ stall test show me, Would I get boost before it stalls?

the_riddler said:

and not too worried about the MOT I have all the bits so can put it back for the test.

Click to expand...

And C&U regs ?

the_riddler said:

What would the TQ stall test show me, Would I get boost before it stalls?

Click to expand...

If you don't you've got some serious problems !

If this was a D2 the first thing I would look at is the exhaust manifold to see if it has a leak. If it does, the sound it makes can sound very like a turbo whistle.
But this is a D1, so I don't known if it likely to be the same thing.

Stanleysteamer said:

If this was a D2 the first thing I would look at is the exhaust manifold to see if it has a leak. If it does, the sound it makes can sound very like a turbo whistle.
But this is a D1, so I don't known if it likely to be the same thing.

Click to expand...

I don't think it's the manifold as I've changed it and it did the same with both old and new.

the_riddler said:

I don't think it's the manifold as I've changed it and it did the same with both old and new.

Click to expand...

Sorry thought you meant just the inlet manifold. Have you tried getting someone else to rev it till it makes the noise then going round with a stethoscope to localise the noise? that's what I'd do now.

Disco1BFG said:

And C&U regs ?

Erm lol well I only just found out the egr removal would affect this so not entirely sure yet but it's on my drive for now as its not my daily driver so I'll tackle the siren the. Look at what can be done about the egr I guess.



If you don't you've got some serious problems !

Click to expand...

OK I will try and give this a go and hope this throws up the culprit. It won't be for a few days as I'm moving my daughter to uni today so if you have any more thoughts please keep them coming

the_riddler said:

Erm lol well I only just found out the egr removal would affect this so not entirely sure yet but it's on my drive for now as its not my daily driver so I'll tackle the siren the. Look at what can be done about the egr I guess.

Click to expand...

It's worth a very thorough and very careful read of the regs ....... it has to be fitted ....

Stanleysteamer said:

Sorry thought you meant just the inlet manifold. Have you tried getting someone else to rev it till it makes the noise then going round with a stethoscope to localise the noise? that's what I'd do now.

Click to expand...

No worries I think I might have to try a tq stall test to see what it throws up

Disco1BFG said:

It's worth a very thorough and very careful read of the regs ....... it has to be fitted ....

Click to expand...

Cheers for the info is there no way around removal? Although honestly I can't see a difference since I removed it but if I'm loosing boost nothing will make much difference I guess. I'll just refit it if there is no work around.... Man I need another v8!!

Disco1BFG said:

removing your EGR valve will make it fail the MOT - So .......

Click to expand...

If it's the part I'm thinking of that you mean that's not the case, I have no EGR valve in mine, it was removed by the previous owners and it has passed MOTs for decades. I was told it was the last bit of electrical control over the engine (being the part that dealt with exhaust emissions).

BuzzLand said:

If it's the part I'm thinking of that you mean that's not the case, I have no EGR valve in mine, it was removed by the previous owners and it has passed MOTs for decades. I was told it was the last bit of electrical control over the engine (being the part that dealt with exhaust emissions).

Click to expand...

Thanks for the info matey, I'm not sure if yours is an edc version or not but I have just spent an hour reading up on the guys that have blanked their egr on a 300 with edc and literally 100s are saying it's all fine??? Would be great if someone could let me know what results they have had with removing the egr on an edc 300??

I'll probably start a new thread but if anyone is reading here please let me know and Disco1BFG have you actually had experience of the edc version emissions being affected by egr removal?? There seems to be loads of people that don't have a problem with it?

I'm pretty new to the 300tdi but have 25 years of tinkering with hobby cars in one form or another so I can make sense of what is going on I just need the real world facts rather than what is printed in guidelines and manuals etc. Cheers guys!

BuzzLand said:

If it's the part I'm thinking of that you mean that's not the case, I have no EGR valve in mine, it was removed by the previous owners and it has passed MOTs for decades. I was told it was the last bit of electrical control over the engine (being the part that dealt with exhaust emissions).

Click to expand...

the_riddler said:

....... and Disco1BFG have you actually had experience of the edc version emissions being affected by egr removal??

Click to expand...

Emissions are not the issue - the regs state that the EGR must be fitted - it's been done to death on here - probably about the time the regs changed in May last year IIRC.

Historic passes are irrelevant - what matters is; if it was fitted at the factory, then it must be fitted now. And VOSA can tell this from the VIN. Even if the MOT tester turns a blind eye, then, in the event of an accident and a potential vehicle inspection - there is the potential for your insurance company to say that it doesn't meet C&U regs and therefore you are not insured .... You might consider this scare mongering or just plain rubbish - I don't - it's your call - depends how much corporate bullying you think you have the stomach for.....

Both our D1's have the EGR's fitted, and the MOT tester did check, quite thoroughly, that they were present too.

In terms of EDC, yes, sadly I have plenty of experience of it, so much so, I took it off my D1 auto.

As it happens, both our smoke test results are very low - IIRC, round about 0.2 - so, significantly less than the limit of 3.

BuzzLand said:

I was told it was the last bit of electrical control over the engine (being the part that dealt with exhaust emissions).

Click to expand...

There's a reasonable explanation of EGR here:-

https://en.wikipedia.org/wiki/Exhaust_gas_recirculation

@Disco1BFG and others, if you go to https://www.mot-testing.service.gov.uk/documents/manuals/class3457/
Quote "8.2.1.1 Exhaust emission control equipment
This inspection is only for vehicles that must have a full catalyst emissions test (disregarding the basic emissions test). You only need to check components that are visible and identifiable, such as catalytic converters, oxygen sensors, and exhaust gas recirculation valves." end quote
So you'll find under 8.2.1.1 That if your vehicle has a cat, you'll also need the EGR valve and ancilliary equipment. If no cat, no need. My Anniversary model, even though being one of the last Disco 1s made, has never had a cat thus I am quite at liberty to remove the EGR.
UNLESS, and this is a big unless, they have changed the regs since I have been in France, i.e. since beginning of May. If in doubt, get you MOT tester to show you the relevant section of the updates, which come out every five minutes. MAYBE, they are now saying that even if you don't have a cat, you now need EGR, cos it was originally fitted, I don't know, but that is how it was 4 months ago.
You used to be able to see and download the MOT testers manual, updates and all, from the gov.uk website, but now you can only see it if you log on and to log on you now need to work for or own a garage or MOT testing facility, or work for VOSA, which is a crying shame and possibly illegal.
MPs should tell us why we cannot read the regs that govern our cars.
But I went to the log in page, read the blurb then noticed that from the bottom of that page I could still look at the older version, which I doubt will have had this removed in the new version.

Disco1BFG said:

Emissions are not the issue - the regs state that the EGR must be fitted - it's been done to death on here - probably about the time the regs changed in May last year IIRC.

Historic passes are irrelevant - what matters is; if it was fitted at the factory, then it must be fitted now. And VOSA can tell this from the VIN. Even if the MOT tester turns a blind eye, then, in the event of an accident and a potential vehicle inspection - there is the potential for your insurance company to say that it doesn't meet C&U regs and therefore you are not insured .... You might consider this scare mongering or just plain rubbish - I don't - it's your call - depends how much corporate bullying you think you have the stomach for.....

Both our D1's have the EGR's fitted, and the MOT tester did check, quite thoroughly, that they were present too.

In terms of EDC, yes, sadly I have plenty of experience of it, so much so, I took it off my D1 auto.

As it happens, both our smoke test results are very low - IIRC, round about 0.2 - so, significantly less than the limit of 3.

Click to expand...

You'll have seen my other post on this by now. To be honest, EGR on or off, the emissions test showed nothing to worry about, the big factor in mt experience was when "city diesel" came out. My MOT tester told anyone who failed emissions to go and tank up with it and drive around for a while before coming back for a retest, they all passed. Of course I think all types of diesel are the equivalent now. So, unless all your D1s had cats, I'm surprised your MOT testers even looked for EGRs.

I am furious about this and have just emailed Gov.uk for an explanation.