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Discussion Starter #1
Right......

Just a bit of thinking out loud here. I doubt anybody will have the answer. Since it was re-assembled there has been, what I assume to be, a boost leak. Basically, a high pitched scream as boost is created.

Goes when i take my foot of the pedal
Happens at all revs in 5th (65mph up)
Doesn't happen in 1st
Builds from 2.5k revs all the way up to the redline in 3rd & 4th
I can smell diesel fumes in the engine bay again (but no injector chuff)
Is really fecking annoying!

I've been under the van today and found the same sort of carbon build up on a bit of the turbo that you get around the leaky injectors. I'm not sure if this recent or is a result of the tar dripping out of the injector area and onto the turbo previously. Have chipped it off and will see if it returns. Thought I was done with the coal!

Have taken all induction/charge hoses off and checked for splits/holes/signs of oily residue where pressure might be leaking. Have also replaced all jubilee clips and tightened up as tight as possible without stripping threads. Only place I found a oily residue was the hose at the bottom of the intercooler.

As such, I'm now pretty convinced this is a leak on the exhaust input/output part of the turbo but I need to check my understanding of the operation of the turbo is correct:

1) Engine off - no Vacuum on wastegate actuator (wastegate closed) - lever is out

2) Engine on - wastegate actuator moves in due to vacuum and wastegate is open, turbo is spinning and no boost is made

3) Revs rise and ECU uses vacuum to progressively close wastegate based on throttle input etc until wg is fully closed and full boost is created

4) Foot off accelerator, wastegate opens and charge pressure is released.

So surely, if it was leaking exhaust fumes either side of the turbo, I would be able to hear it all the time and it wouldn't be dependent on the charge pressure, but would rise and fall with the revs as this side of the turbo doesn't become more pressurised as charge pressure increases?

Other thought is vacuum leak, but where? If it was the vacuum system attached to the boost sensors/controllers, it would stop it actually making any boost as the wastegate actuator wouldn't be functioning, so it would be in failsafe "noboost" state?

I'm proper out of ideas at the moment.

I need a better check for boost leaks rather than visual inspection. Filling system with smoke might help spot leaks. Maybe it's time to get the bong out of retirement and see if helps locate leak/inspiration mwahahahaha!
 

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I now have this image in my head of a bong constructed from turbo hoses :rolleyes:

The v-class turbo bong:thumbsup:

can you get the squeal by revving while in neutral?

obviously not a vacuum hose as you've already worked out.

if it's boost related then surely you would get the squeal at the same level of boost whatever gear your in?

it may be something completely unrelated - have you checked v-belt tensioner? I had a really annoying squeal a while back once i got over 40 - after 2 weeks of checking various things it turned out that the casing on the nearside mirror wasn't seated properly (I think someone had knocked it in a car park)

I'll keep racking my brains to see if I can come up with any other likely causes
 

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Discussion Starter #3
Yeah, I can get it to make the the noise at about 4k revs in neutral. Not overly happy doing so, the clutch switch limiter is there for a reason I guess. I did have a shufty under the van whilst somebody else revved it and boost actuator arm only moves fractionally at the top end of the rev range so I guess the ECU limits the boost in neutral as it doesn't really need it then, boost can't be equal all the time I guess.

I'm going to either build or fudge some sort of device to introduce compression into the charge air circuit up to 15psi so it should squeal then if it's a boost leak and enable me to try and find it.

So either something like this or by restricting the exhaust so it builds pressure in the system.

Bit wary of the latter as it makes it difficult to gauge how much pressure is in the system and I don't want to create more problems lol.
 

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Discussion Starter #4
Just for the record..... this is now fixed.

When I took apart the manifold to sort the leaking injectors I had apparently dislodged the captive nut affair that sits in the lower half on more than one of the bolts that hold the two halves of the manifold together. The one that also holds the oil filler and 2 more at that end. Half an hour and some impact adhesive later the nuts were re-fixed and whistle was gone.

Happy :)
 
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