Hi guys,

I'm loosing my mind. 

7 mechanics and no fix.

2022 2.0tsi Kodiaq (DNNA engine code)

40k miles

Despite being under warranty, I'm already out of pocket £1550 because "there is nothing wrong with the car".

Car spent a total of 18 working days across 3 garages.

2x Skoda dealers and 1x Independent Specialist place with outstanding feedback and a great bunch of guys.

The issue.

When accelerating car makes a kettle whistle noise and wooshing/boost drop noise when lifting throttle.

Every time no matter the speed or revs.

Overboosting like.

Back in February, car was only making a whistle noise when accelerating, suddenly on a motorway. Stationary, nothing.

In May this got slightly louder and now you could reproduce the whoosing/dumping excess boost sound reving in stationary, but no whistle.

No fault codes, ever.

On a handful occasions I experienced a hesitation when pulling away, press throttle, nothing nothing and then full power. No fault code no ELM even for a second. Not sure if related.

4 master techs with combined 110 years experience can't figure it out (dealer and indy) plus 3 non master techs.

Work done so far:

New PCV valve

New Air/Boost pressure relief valve (by the turbo after the air intake pipe).

Entire intake and charge system stripped, checked for cracks and any blockages. Every pipe and clip inspected, even a camera inside the intercooler.

Boost pressure cleaned with alcohol.

Brand new air filter, no splits, airbox fine too.

Air leak test x2.

You name it.

Sound is located on the right hand side near the air intake, valve dropping/diverting excess boost back in the air box. 

No idea where the whistle sound comes from as it only happens under load.

If you can help, please watch the entire video, sound only.

Thank you very much guys, much appreciated.

Was the charge air system pressurized with pressure and mist and then tested for leaks after 2-4 hours?

Apparently, yes.

Have you tried a length of hose one end to your ear and the other moved about engine bay. It may help narrow down where the noise is coming from. Son in laws td5 landrover makes a whistle noise due to bad exhaust manifold gasket but only at higher revs when turbo kicks in??

Alasdair

The wooshing sound is 99% air being dumped back to the air box. It’s clear as water. The whistling sound only under load.

I’ve spent another hour today with the camera looking all around the exhaust side, hot side of the turbo and no signs of the blow by. Nothing, around the gaskets or clamps.

That sounds like a nightmare to track down. Only thing I can think of is the original boost pressure relief valve was faulty and maybe the new one as well or pressure sensor sending wrong info to ecu. My old 1.9tdi used to overboost randomly due to a sticking actuator but generally it went into limp mode and threw up a code. The fact that you have no codes is a weird one.

Alasdair

I mean what are the chances of a brand new genuine diverter valve being faulty?

Unless they manage to damage it somehow to save the embarrassment.

I was convinced this was it but due to a valid warranty on the car I had to pay them to replace it.

No codes, ever.

It’s one of them faults thet keeps you up at night to the point you start questioning your sanity, BUT I know this ain’t normal, period.

I mean I could buy another diverter valve.

Should it try older 06H145710D instead of what’s on the car 06N145710B?

I’ve got a genuine air filter coming too.

It appears that filter isn’t brand new, just a very very clean 4 years old filter.

Another thing I haven’t tried is replacing both sensor, bottom charge pipe and manifold past throttle body.

Edited 6 July6 Jul by MRC00

First one is the older version apparently (white background) while the second is what’s on the car right now.

Have a look on lllparts original manufacture diagrams to see what should be fitted in case its there is a difference. I know they changed design at some point but not sure when. Might be worth changing pressure sensor. Unless the bottom pipe and manifold are leaking I doubt it would be them. I read to check divertor valve you can put 12v accross terminals and it should operate instantly. If its slow or sticking/intermittant then its had it.

Alasdair

Hi Alasdair,

Diverter valve it's brand new fitted by Skoda 3 weeks ago and it has made no difference, but I doubt it's faulty. They hardly ever go wrong, but I reached the stage where I had to do something after spending £1350 on diagnostics. Diverter valve was £150 fitted.

Long shot I know but as you have tried just about everything maybe inlet valve not seating properly? Have heard it can cause back pressure into air filter housing.

I think your turbo is like mine and uses variable geometry tech. If the veins are warped or damaged/severly stuck it can I think cause the same symptoms by forcing air back into inlet then filter although I would have expected a code. Asked an old mechanic and he mentioned turbo/compressor surge. I Maybe clutching at straws here but would love to know the reason why.

Alasdair

Trust me, there is already a long line of people dying to find out what it is ;)

Inlet valve? You mean the diverter valve I replaced? If so, what are the chances of original and new one not sitting right.

Also, first 3 months no issues, it just suddenly happened at night on a motorway.

One thing I noticed, during extreme heatwaves, the whistle is louder and immediate where in cold temps more tone down.

What does he mean by turbo / compressor surge?

I’m new to turbo engines

I’ve got a ramp booked in this Thursday for a whole day with dealer level diagnostic tools and another hobbyist mechanic with excellent record of fixing **** everyone failed to identify.

While not knowing your car it reminds me a bit about my old Seat Exeo, it had 2 intercoolers in front of the front wheels in the bumper from time to time there was a whooshing noise but not all the time, i couldn’t work out where the noise was coming from until the seal popped out between the plastic and the aluminium cooler when it gave up completely the car lost all boost (on the M6 in the right had lane while overtaking) and went into limphome mode then i could rally hear the noise while driving but not on tic over,, i ended up getting a stick on the accelerator to try and replicate "driving at speed"

might be worth a look if the noise is coming from the intercooler area

Cheers Greebo

That is very interesting. I think while I’ve got a ramp booked this Thursday for a whole day, I will remove the front bumper and inspect intercooler properly.

The underload whistle annoyingly comes front the exactly same area, top passenger side. It’s so characteristic and loud it kind of makes it easy to pin point the location from the cabin.

This is why I changed the diverter valve, well Skoda did, because a failed valve would produce both noises, the under load whistle and that wooshing boost sound when releasing throttle.

I see if I can replicate the whistle in Drive on the ramp, that while 100% confirm the location.

As mentioned already, the wooshing is defo an excess of boost being pushed back the the air box way, it’s clear as water but if the whistle comes from the same location then I have no bloody clue what to look for other than trying another brand new diverter valve?

Thank you for your input, I appreciate it.

Same goes to Alesdair and everyone else who replied so far.

I mean it.

I used to was very active on Audi A8/S8 forum helping people every day from fault finding to actual fixes and retrofits but this bloody car and engine drive me insane.

I actually lost sleep because of it because I will not accept Skodas “it’s normal, they do that” until I find the issue.

As I said I don’t know the layout of your car, so don’t know where your intercooler or coolers are, my Exeo was the 170 BHP so had two rather than one in front of the passenger wheel and a connecting pipe in front of the drivers wheel, it was a drivers one that gone, in my case… so not sure if it helps, but if it gives you something else to check out then it may give you some ideas

Good luck

Has a proper diagnostic log run/Drive been performed where the target and actual boost pressure values are recorded?

Edited 7 July7 Jul by Cairus

Gen 4 2.0 TSI has only one intercooler in the center.

One of the aims this Thursday is to compare things such as target and actual boost to determine if the car is over boosting due to maybe a false reading or is it an air leak or f knows.

I should have more answers on Friday.

When I said inlet valve I meant the inlet/exhaust valves on engine. If an inlet valve isnt seating properly you can get back pressure through the inlet system. As for turbo veins the turbo uses variable vein. If they are clogged or worn/damaged it can mean they dont adjust properly causing too much boost when you lift foot of throttle which can cause air to be forced backwards. Difficult to explain but pulled this off google

Low Mass Flow: During low-speed, high-load situations, the engine's demand for air is too low for the amount of boost the turbo is trying to generate. The compressor blades essentially stall, losing their grip on the air and causing a pulse of reverse airflow.

Hope the mechanic can find out where the problem lies.

Alasdair