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?