Engine hissing on partial throttle, EGR deleted

[Quiorky]

2019 Startline Manual 84bhp
I've had a hissing noise from what sounds like the drivers side of the engine bay for a little while now, although only happens under load so hard to be certain. The van had an EGR insufficient flow error code so I assumed it might be linked to this, having done some research. The EGR pipe was partially blocked and the cooler was also fairly clogged, so I opted for an EGR delete (blocked off pipe) and got it coded out.
However the hiss still remains. Having done a bit of playing it only occurs on part throttle when below 2k rpm, but it goes away on anything more than part throttle below 2k or any throttle level when above 2k. In my limited knowledge it feels like a boost leak as when the hissing stops the engine is more responsive, almost like a valve is closing when the throttle is opened more or revs are higher. Also below 2k, if I gently play with the throttle I can hear the hiss go up and down and it effects the engine power, again more responsive once the hiss stops (valve closes?). From what I've read the the Tdi engines don't have a recirc valve when off boost, happy to be corrected, so i'm struggling with what the issue could be.
For info since the EGR delete and code out, there are no error codes at all, and it's been driven regularly for a month or so since.
Any help appreciated.

 

[Quiorky]

Could anyone help with this please? I'd love to have a go at fixing it if there's some straightforward troubleshooting i could do, thanks

 

[James147]

Have you had a good look round the intercooler ? I had similar issues and that was the cause

 

[JDC]

I had a hiss/whistle type noise and thought it was a turbo knackered. Looked further and found the intercooler could be at fault. If it's the intercooler then no errors will show up as the leak is before the turbo on the intake, this doesn't tend to make much noise unless under load. Take the front bumper off and it's right at the front, really easy to do. Mine was slightly corroded and had a hole in it.

 

[Quiorky]

Great thanks both i'll take a look. It definitely seems to only be under load so i'm hoping its a straight forward fix and not the turbo. @JDC did you you have to replace the intercooler?

 

[JDC]

Yes, replaced it. OEM spec is Mahle/Berh, I got one from Euro car parts. You may be able to see it once the bumper is removed. I think there's some video and plenty of explanations on how to remove the bumper if your doing it yourself. It's easy enough to do.

 

[Quiorky]

Thanks, yeah done the bumper a couple of times for headlight issues so happy with that bit. I'll let you know how i get one

 

[The Bear78]

2019 Startline Manual 84bhp
I've had a hissing noise from what sounds like the drivers side of the engine bay for a little while now, although only happens under load so hard to be certain. The van had an EGR insufficient flow error code so I assumed it might be linked to this, having done some research. The EGR pipe was partially blocked and the cooler was also fairly clogged, so I opted for an EGR delete (blocked off pipe) and got it coded out.
However the hiss still remains. Having done a bit of playing it only occurs on part throttle when below 2k rpm, but it goes away on anything more than part throttle below 2k or any throttle level when above 2k. In my limited knowledge it feels like a boost leak as when the hissing stops the engine is more responsive, almost like a valve is closing when the throttle is opened more or revs are higher. Also below 2k, if I gently play with the throttle I can hear the hiss go up and down and it effects the engine power, again more responsive once the hiss stops (valve closes?). From what I've read the the Tdi engines don't have a recirc valve when off boost, happy to be corrected, so i'm struggling with what the issue could be.
For info since the EGR delete and code out, there are no error codes at all, and it's been driven regularly for a month or so since.
Any help appreciated.

Assuming that the EGR is still fitted, were all of the pipes blanked off? You say "pipe blanked" but I think there is more than one.
Have a look at the corrugated pipework around the EGR for signs of a crack. Sooty deposits are a giveaway. This is known to create a boost leak sound (because it is) and is quite common.

 

[Quiorky]

The EGR valve is still fitted but I've removed and blanked the pipe before it, the one with the corrugated part at the back of the engine that normally cracks. The pipe itself was fairly clogged (but not cracked) and so was the valve from what I could see. The hissing was there before and after the blanking so it doesn't seem to have made a difference, apart from no longer constantly getting the 'insufficient air flow' error. But I'm no expert on the system so if I should be checking the valve as well then I will, would I need to remove it completely?

 

[Quiorky]

So I’ve taken the bumper off to check the intercooler, but it looks like I don’t have one! Is that possible? I thought they all had one. Have traced the pipes from the main rad and the front one and they both hook into the coolant system, not exhaust.
So unless I’m missing a hidden intercooler, doesn’t look like that’s the issue annoyingly

 

[The Bear78]

Is there a chargecooler sat on top?

 

[Quiorky]

Thank you, yes there is! So could this be the issue or because it’s a changecooler mean that this is unlikely my problem?

 

[The Bear78]

It could be, as the air still passes through it. See if it's leaking!!

 

[JDC]

Take the black plastic trim off. Should look like mine. It's the smaller one at the front. Mine is a 16 plate 140ps.

 

[Quiorky]

Thanks it's definitely a charge cooler on top of the engine rather than an intercooler at the front. It doesn't look like yours @JDC but thanks for the pic. Is the best way to look for leaks to use soapy water at the connections? I've had a look and can't see any obvious fluid or oil leaking, but i guess i may not

 

[JDC]

Mine had gone rusty at the back. Couldn't see it until I removed mine. I would be reluctant to put cleaning products in it as it needs to dry and free from contaminate as it should feed direct into the turbo.

 

[Quiorky]

Thanks for everyone's help. I've done a pressure test and cannot see any loss using a pressure tester. I also used my obd11 and monitored boost pressure differences between actual and requested and there's only max 0.3bar difference at worst and only on a handful of occasions on a 30min trip. i'm at the end of my knowledge so it's booked into SR Autoworx in Gloucester who came highly recommended, so i'll let you know the outcome.

 

[Hughes199]

Thanks for everyone's help. I've done a pressure test and cannot see any loss using a pressure tester. I also used my obd11 and monitored boost pressure differences between actual and requested and there's only max 0.3bar difference at worst and only on a handful of occasions on a 30min trip. i'm at the end of my knowledge so it's booked into SR Autoworx in Gloucester who came highly recommended, so i'll let you know the outcome.

Any news? I have the exact same problem as you and have also done the same troubleshooting but still none the wiser

 

[T12]

Following this, I have same problem, 140hp euro 5 T6.

 

[Quiorky]

Quick update, it went into srautoworx last week for a diag. It seems there’s a leak back up from the turbo out of the air intake ie the wrong way, so he reckons a diaphragm’s gone somewhere. To diag it he took the pipe off the top of the air box (that goes to the manifold) and revved the engine. Mine made a loud whooshing noise as the revs dropped, as the turbo pushed air back up the pipe, it was pretty obviously wrong. It’s booked in on Friday to get it hopefully sorte so I’ll update after that