Fuel Tank / Pump Hissing (Washing-Machine) Noise

[Lady T]

Hi

I have just picked up my brand new T32 204ps 4motion and it has driven like a dream for 10 days the engine has been purring so beautifully quiet. I filled the tank up with fuel on the 10th day and drove off with a terrible hissing sound coming from the fuel pump just below the fuel caps and a terrible washing machine sound with a gouging of fuel that went to the back of the van and then glugged back to the front area of the van swishing with gallons of fuel and the fuel pump gets louder and louder with a terrible hissing pressure sound that is continuous! I immediately called VW Assist to come to the vehicle as I was not taking any chances, the VW Assist were very detailed and said that they had not come across this problem before and it was important to return to dealership as it sounds like a faulty fuel pump! I have returned the van to the dealer and they have said they feel this is the normal sound to this van! I have hired and driven High Spec VW vans for three years before I knew the exact VW Spec and I have never come accross this problem please can anyone Help?

 

[Zave]

It should stop after a few fills. Mine and many others have suffered the same.

 

[Lady T]

Hi Thank you for replying to the post and problem, You say you had a similar problem was this with the Fuel pump loud hissing!
The fuel tank sloshing is really clear to me now as they New Fuel tanks on newest models with ad blue since 2015 are one big open tank without any baffles in side to prevent the fuel sloshing about like a washing machine! This is a manafacturing design that causes the fuel to slosh about! The VW mechanic says it is up to all the new T6 owners to come forward with the fuel tank sloshing problem so that enough people can make the changes to manufacturing tanks with baffles to stop this sloshing! This is an All together can make changes to how the tanks are manufactured!
I have had quite a difficult time with the dealership a VW Technician working with the problem of an extra loud fuel pump that is hissing ridiculously.... At VW dealership/Service Centre they put the van up on the ramp and showed Me the fuel tank and fuel pump underneath and the VW Technicician says it is an amplified noise to normal.. they took a video of the sound and sent it to VW uk to send to Germany.. I questioned the method and source of a mobile phone recording and they played it to Me and it is difficult to truly diagnose the problem! VW Germany say it is normal and the VW Technician at dealership agree with Me that it is louder than usual!
I have been told to drive this around and record this sound and get back to VW dealership!
I have lost My confidence in this dealership and Van service centre as they have not worked on this spec of a van before and they are only relying on a sound example taken from a mobile telephone!
Can You and anyone on this T6 forum recommend the best VW Specialist Van Centre with Technician’s and Mechanic’s experienced with working on T32 204 4Motion in England so that I can get some experienced help with this fuel pump issue as London is looking very poor with experienced VW Van service centre’s!
VW dealership/service centre Citygate have advised that I get a second opinion from an experienced VW Tech/Mechanical team experienced in working with this Model and Spec VW T32.

 

[mmi]

Hi Thank you for replying to the post and problem, You say you had a similar problem was this with the Fuel pump loud hissing!
The fuel tank sloshing is really clear to me now as they New Fuel tanks on newest models with ad blue since 2015 are one big open tank without any baffles in side to prevent the fuel sloshing about like a washing machine! This is a manafacturing design that causes the fuel to slosh about! The VW mechanic says it is up to all the new T6 owners to come forward with the fuel tank sloshing problem so that enough people can make the changes to manufacturing tanks with baffles to stop this sloshing! This is an All together can make changes to how the tanks are manufactured!
I have had quite a difficult time with the dealership a VW Technician working with the problem of an extra loud fuel pump that is hissing ridiculously.... At VW dealership/Service Centre they put the van up on the ramp and showed Me the fuel tank and fuel pump underneath and the VW Technicician says it is an amplified noise to normal.. they took a video of the sound and sent it to VW uk to send to Germany.. I questioned the method and source of a mobile phone recording and they played it to Me and it is difficult to truly diagnose the problem! VW Germany say it is normal and the VW Technician at dealership agree with Me that it is louder than usual!
I have been told to drive this around and record this sound and get back to VW dealership!
I have lost My confidence in this dealership and Van service centre as they have not worked on this spec of a van before and they are only relying on a sound example taken from a mobile telephone!
Can You and anyone on this T6 forum recommend the best VW Specialist Van Centre with Technician’s and Mechanic’s experienced with working on T32 204 4Motion in England so that I can get some experienced help with this fuel pump issue as London is looking very poor with experienced VW Van service centre’s!
VW dealership/service centre Citygate have advised that I get a second opinion from an experienced VW Tech/Mechanical team experienced in working with this Model and Spec VW T32.

Interesting read. I can’t understand what can make the sloshing sound in your van. I’m currently driving a very similar van to yours – though just panel van, 3 three weeks old, 204ps, T32, 4motion. It’s LHD so I’m sitting very close to fuel tank. And, there is no way to make fuel move so that I could hear that. I did seriously try - stopped, reversed, stopped, did all kinds of acrobatics on the road. Now it had half tank. I did try that earlier with more fuel in the tank. Nothing. The same was with my earlier one (similar van from late 2015) – at least nothing that would have drawn my attention on that.

This is probably farfetched but there is a kind of one-way valve at the bottom of filler tube. I think one of it’s the functions is to ease out filling the tank by not letting diesel foam to flow back to the filler tube. In my another car there is not one and the foam comes up from filler and I have to stop for a moment and let the foam turn back to liquid – doing that a few times I can put additional 10 liters into tank. But that doesn’t happen in T6 (and not in T5). Another function of the valve might be to prevent stealing the fuel. Just thinking if that valve has broken loose, it would allow the fuel flow back and forth up to filler tube when you slow down or accelerate. And I could imagine that would make loud sloshing noises in the filler tube.

I have difficulties believe that the fuel tank construction has been changed dramatically - unless they did that in last few weeks.

The noise from fuel pump – I can’t hear anything on mine. If you do a recording, perhaps you could post a clip here please.

And yes, I also find strange way to do recordings by mobile phone at the garage. But good thing is that the phones are everywhere and from customer’s point of view it is sometimes good evidence. But unfortunately what comes to strange noises – by phone it is difficult to catch the essential, unless it’s something disastrous.

Another method used by VW is to ask local garage have another similar van and compare then those. That works of course only as long as the fault is not by design.

 

[Lady T]

Thank you for replying again...
I took every moment to have every part explained and checked from the fuel take system and yes I pushed to have the section from inlet pipe to fuel tank explained and confirmed checked... this part being the safety back flow valve on tank preventing fuel from flowing out of the tank during an accident or if the van is flipped over in any event... the VW Mechanic says this is all ok from what he can see as he took the tank off the van and examined this when he was taking the high pressure fuel pump out. I still questioned.. with a high pressure filter and pressure being held in this tank could this effect the tank back flow valve causing any of the 2 issues I am finding as faults at present 1) loud hissing sound akin to a broken toilet system coming from the fuel pump and 2) sloshing fuel sound akin to a washing machine sloshing with a load... to which the Mechanic replayed no this fuel back flow valve can not cause any of your issues.
Thank you so much for doing a Fuel Tank Sloshing test.. Excellent... No sloshing...
I would love to hear from anyone else who has tested the Feul Tank sloshing or can ad any experience and knowledge to the Fuel tank design and no baffles in T6 Euro 6 tank design.
I thoroughly questioned as I examined the fuel tank with the mechanic whilst the van was up on the ramp and continued to ask questions even though the answers kept coming back regarding the whole one large hollow tank without baffles explanation/theory... I was shown a Van in for service an early 2015 model in repair and up on the ramp next to Me, I interestingly kept pursuing the tank sloshing and reason’s given to Euro 6 fuel tank hollow and no baffles...the VW Mechanic explained as he showed me the underneath area of the earlier model van/fuel tank before ad blue was introduced and this was a Transporter van with one single large tank fitted left side, the same tank shape in design as the T6 Euro 6, the mechanic explained that this earlier model tank pre ad blue and pre Euro 6 was the same looking tank on the outside and the inside of this tank design has the baffles inside to prevent the fuel from sloshing about.
The fuel pump loud hissing sound is in the VW mechanics opinion “amplified and is louder than other vans he has worked on!. I have questioned the diagnosis and sound recording by mobile telephone as a true source of giving an accurate sound level testing and diagnosis for a VW Dealership or VW UK to professionally assess mechanical data in testing this way! Whilst I agree this is a vital aid and assistance for us as owners to take recordings by way of mobile phone video and to provide these as aids and proof to VW Dealership/Garage and VW Uk to then assist them along with the correct professional VW Technical sound level diagnostics and VW data/fault testing equipment... A mobile phone sound recording with a mechanic in the back of a van is laughable and is certainly not a true sound or sound level diagnostic or Fault diagnostic for VW and is certainly not professional and accurate enough evidence to asses and to be dealing with issues and Euro 6 Fuel Tanks and Delphi High Pressure Fuel Pumps to be truly a precise diagnosis.
It would be very interesting to do a side by side analysis of the same spec van however the dealership have never worked on this high spec of a van as they keep saying!! and this I find the strangest... They can sell this spec of a van however they can not deal with any problems or issues concerning this spec of a van... Just 10days after competing the sale...All technical support with VW franchise Citygate is via internal messaging and email sent to and from VW UK... they are not even allowed to talk directly to the VW Tech Team in Manufacturing in Germany!
I really am in need of some advise as to who are the best independent VW Specialist Garage’s with experienced Tech/Mechanics outside of London with the knowledge and diagnostics to work with T6 Euro 6 Fuel system diagnostics/T32 204 4Motion and help me with this matter of diagnosis and the two issues I am dealing with

 

[Shredder]

A bit confused as to why you want an "independent VW specialist garage" when, whatever it may be, is a warranty issue ?? Independents are not allowed to carry out warranty work.

It's a bit of a trek but Volkswagen Van Centre Sheffield (JCT600) deal with a lot of T32 204 4Motions as they do all Leighton Vans VW work and nearly all the vans Leighton sell are these top spec ones. Mine has just been up there for warranty work (and I'm down in Surrey) albeit a different issue. They were very good and also know how to look after expensive kit as they are used to it. Ask for the Master Technician nicknamed "Foggy" to look at it.

Hope that is some help

 

[Lady T]

Thank you so much for replying... Sheffield... Leighton Vans VW, great I have read about them a few times in articles...No where is a trek when they are experienced and skilled VW Specialists... Our VW Vans are our babies and we go anywhere for specialist care.. like searching for doctors... I agree this is a VW Uk warranty issue! And a Citygate dealership issue!,. and I am pursuing VW UK with this issue of the two faults mentioned and the issue of Citygate’s inexperience and crude mobile phone video methods used to diagnose these issues, I have also pointed out to VW UK that we are only dealing with the warranty and faults in factory manufactured parts.
An experienced VW Technician experienced in this spec of a van is vital to a swift and accurate diagnosis and one that is essential regarding VW warranty works as I am learning fast... then it goes without saying...regarding the future with maintenance and servicing and repairs.. We all want an independent VW specialist and Master Tech with the skills to keep this spec of a van driving at its full performance and ultimate potential...
Thank you and I will get into contact with Foggy Master Tech at Leighton Vans VW

 

[Shredder]

Just to be clear. I am saying that the JCT600 Sheffield Van Centre is an official VW van centre/dealer and part of the JCT600 group. This is the van centre that Leighton Vans choose to work on their vans. The VW Van Centre Sheffield is not part of Leighton Vans.

The Master Technician known as "Foggy" works for the Sheffield VW van centre but is the person that specifically works on the Leighton Vans. VW Sheffield Van Centre are on: 0114 282 5708

For non-warranty work like servicing, customisations and tuning mods I would use the independent VW specialist Bognor Motors (@BognorMotors ). Mine is currently there for the first time and so far the care and work has been outstanding. I will be going there myself for everything non-warranty

 

[Lady T]

Thank you... that has cleared me calling the right place... for VW sheffield van centre and Foggy Master Tech... thanks for telephone number.. great warranty and VW work.
Bognor Motors for the servicing customisation and all important tuning...
This is valuable shared information... I am truly grateful

 

[Loz]

This is a fascinating if not strange issue. I wish we were closer as I would love to understand your issue.

Just to be clear, have you ‘brimmed’ the fuel tank so that is too full to slosh about? and then how much fuel do you have to use before you start to notice it?

 

[Lady T]

Thank you for replying again... Hi Loz
I picked up this gorgeous van on April 10th... I drove away and the tank was just over half full... The van drove like a dream.. the sounds were a soft purring engine and I experienced a drive like I had never experience before with the 4Motion hugging the roads and turns...
I spent 10 days driving all around London... great roads for testing vans as terrible pot holes and speed bumps everywhere... I am someone who really listens and feels everything with driving a ‘new van’ so as to get to know every single sound and to understand every single part... so as you familiarise yourself and get to know your new van and it’s characteristics then if any sound is heard that is not usually you can act fast and deal with parts before they cause more damage and fail... I am someone who does not just rely on a computer ECU to tell Me... I can sense... The van drove so amazingly and so quietly ... beyond my wildest dreams...
On April 20th the fuel light came on the dash.. bing... great I felt this was the perfect check to wait till computer says fuel low.. I smiled and said ... fuel low indicator works... check
I filled the tank up with Ultimate Deisel and filled with £80 of fuel just under a full tank..
I put the miles count to 0 to see the miles and fuel for the next week for a consumption guide with My driving.. I then started up the engine and drove off... The hissing sound started immediately with the washing machine tank noises... The hissing was so bad I pulled over and immediately went straight to check the fuel cap... everything seemed ok.. so I cleaned the cap and surround really well and carefully put the fuel cap back so as to feel the thread in... started up the van in stationary parked position and this hissing was not coming out of the cap area... I listen down under the van just behind left side between van wheels and the hissing sound was terrible... I got into drive and thought that drive slowly and maybe it was the fuel pump adjusting to pressure so felt driving may help... the hissing got louder and the sloshing fuel tank was terrible every left and right turn every speed bump and stopping was the big slosh... The hissing and sloshing was so bad that as I have said I immediately stopped parked up and called VW Assist for help...
As I have shared... I drove this van with every one of my senses and in the 10 days prior I had not heard any sounds like this at all, I knew this new van and every sound so well that when this suddenly happened with the fuel pump hissing like a jammed toilet cistern and the fuel tank sloshing like a washing machine! I immediately took action and called VW Assist for help.

 

[Loz]

(thinking) So if the tank was full how could it be the fuel tank sloshing?
(Thinking) As you were driving about with your first tank full by the time that was half empty you would have heard the sloshing sound?
Q: Hissing from the tank, does it stop with the cap removed and can you hear it louder if you put your ear to the open filler neck?
Q: Have you used enough adblue yet to be able to fill that back up?
Q: Are you sure the sills are not full of water?

See this picture of someone emptying water out of a Touareg sill where the chassis sill plugs were full of cavity wax and not self draining, it had the sloshing sound and the water runs out after the plug was removed. I had the same on my nearly new Touareg.

 

[Lady T]

Thank you... smiling.... I have a similar way with questioning sensing questioning...
My questions are many, like all of us, we question and open to all learning...
1. The half tank and just under a full tank...
I questioned...how if by design the tank is open and without baffles does a full tank of fuel sound so loud and sloshing?... one would sense that when there is less open space in the tank, as with a full tank...for the fuel to slosh around less!?... applying this questioning again... one would sense that when there is more open space in the tank, as with a half tank... for the fuel to slosh about more...!? (VW Tech/Mechanic... I can not answer this)
I questioned... Can a full tank slosh like a washing machine because the fuel pump is not aligned and is sloshing around in the fuel tank? (VW Tech/Mechanic... No the fuel pump is screwed in and fixed and is maintaing the correct pressure in the tank at all times)
I questioned the fuel pump... loud hissing again with regards to... Can a faulty fuel pump that is not a constant hissing sound as this is, but a hissing that builds up and down with amplification in sound, be the pressure faulting and causing the fuel tank and pressure to drop... thus creating the sloshing effect of liquid fuel around the tank with pressure/ gravity and velocity affected with the intermittent pressure dropping!? (VW Tech/Mechanic... The computer/ECU pressure regulatory system would pick this up as a fault and the pressure readings I have checked are 5.79 and the normal is 6.00... this is usual for an engine running in parked position and will pick up to 6.00 when the engine is opened up and on the road driving)
2. Hissing with the fuel cap
My immediate reaction when the hissing started loud was that I had not put the cap screw treads in carefully and locked the fuel cap around enough and pressure from the pump was affecting... This was my first attention... it was screwed in aligned and click locked fine... I unscrewed the fuel cap whilst the engine was turned off, cleaning the cap and threads and around the surround, I started the engine again.... Loud hissing sound started up again.. I was following my intuition... my sensing was that returning the cap and driving along to help everything settle would help Me see if air was hissing out of the fuel cap/sealed.. I sensed that air pressured would have a dampness even a spray residue if this cap or fuel inlet vent was faulty.. After driving only about 100 feet the hissing was building up and I immediately pulled over leaving the engine running this time and parked up, I went around the van to open the fuel caps cover and to see if there was any evidence wet/spray that had been blown out.. I checked... fuel cap and area was clean as a whistle... this is when I started to follow my ear and sensing to hear where exactly was this hissing coming from... if not from the fuel cap and inlet area.. where? I listened and I opened the left slide door so could listen inside and then outside as I slowly tried to sense and pin point the area... underneath the left side from behind the passenger seat to the back wheels listening intently, it seamed to Me to be the whole area and then zoning louder towards the back wheel rather than the front wheel area’s... I questioned in My early post and You so kindly guided Me regarding tank position and fuel pump... left side and not saddled like the T4 days pre ad blue.. when I read this I knew then that I was not going mad with isolating the area’s and faults being fuel pump and fuel tank and not an ad blue problem..
I questioned the VW Tech/Mechanic... The fuel cap is this faulty..? VW/No... The vent just inside the fuel inlet is this faulty?... VW/No...The fuel inlet pipe to the tank is there a pump/or valve?...VW Yes the back flow valve area this was checked and all ok, this is not a pump so there is no noise associated with this part... The fuel pump being faulty could this be one problem part that is creating the two issues?... VW/No we are treating this as two individual issues (This is where my learning was expanded with the Euro 6 tank being one big hollow tank without baffles and this lead Me as I have shared along the Euro 6 tank ‘No baffles’ design explaintion/theory of open tank sloshing given by VW.
10days old... a baby all be it a BigBoy...70 miles only... ad blue so new... I have not even touched...still factory filled n sealed...
3. I questioned... can any fault happen with fuel inlet and ad blue inlet and tanks...
VW.... No they are completely separate... VW showed Me the ad blue inlet and ad blue tank as we stood under the ramped van... explained every part and showed Me the two never meet with the outlet from ad blue tank running through/around over prop shaft to the exhaust right side van, explaining the system of holding the ad blue in one part of the exhaust to treat so to speak and clean for the exhaust emissions to be purified/neutralised and emit the standard Euro 6 emissions.... Still I questioned every ad blue part listening learning sensing and sleuthing!
4.... sills full of water... super photo... I am going to ‘sills examine’ and eliminate this for our information diagnosis data feedback check... I am smiling...as the amount of loud liquid sloshing leaves me wondering... Gallons sloshing sound...
Is this checking the sills of Noah’s Arc!?
Looking at the photo you have shared...Embracing opening and learning, I shall check... in a pair of waders!
Thank you so so much to yourself and everyone on T6 Forum, words can not truly express how supporting and encouraging and caring and sharing this is for Me and BigBoy...
Grateful to be Flying with You

 

[Loz]

 

[mmi]

Perhaps these unresolved mysteries have a connection:
Tick over noise with a sound clip on 29-Oct-2017
Noisy fuel pump MY2018 204

 

[Loz]

Fuel pump or lift pump, lets not confuse them..

 

[Lady T]

Thank you mmi, incredible... I have spent time reading every post regarding the washing machine and for once I was speechless! Then I listened to the sound bite... Haunted by the sound I had to really control myself from turning into the Tasmanian Devil...
Welcome to the 204 club... VW have a nerve! Countless Faults with Fuel pumps!.. Thank you Loz... checked the sills and the seals are tight like a virgin... I know it’s the fuel pump as I have dissected every part and every answer still leads to this being the fuel pump which has been confirmed, is different in the 204’s, and has had many complaints, yet still VW UK keep trying to deflect!
So..... I am saying the Zave mantra....Don’t worry we have all been through this... everything is gonna be alright
Thank you Shredder, I am fixed on the target, VW UK are now listening to Me with regards to Sheffield for experienced VW Tech for warranty, they are arguing that I need to return to Citygate, who inexperienced and on an email training program have been on a work experience trip with My 204 Delphi fuel pump... they have never seen or worked on one before in their lives!...they have broken the seal and examined the fuel pump without a clue with what they are doing and now they have turned the loud hissing into the worst broken ball cock toilet sounds it is so ridiculous, and they returned the van to me saying... we do not know You need an VW Tech expert! VW UK have had my views on this and they have had to accept that I am not letting anyone go any further with 204 fuel pump training programs! And Sheffield is the only place I will accept a second opinion! They are listening to Me now! VW have inherited a brand ambassador wether they like it or not! And this can be 1 of 2 things...Birds of a feather fly together and this can be 1)positive for VW, or this can turn into the polar opposite 2) “Alfred Hitchcock” ...all 204’s with toilet cistern fuel pumps and washing machine’s descending on VW UK HQ!... Thank you to everyone on T6 Forum... I have the target in my sight and I am focused and I am lit up like a blazing Phoenix, I am not going to take a warranty of one fuel pump lying down, considering the serious cost of the entire van! So I am off to VW Sheffield up the M1 with video and sound as I go, saying the Zave mantra, don’t worry.... everything is going to be alright, knowing that every 204 owner past present and future is relying on me to stand my ground and deal with VW UK and this fuel pump issue and washing machine fuel tank in everyone’s highest good...I’m still haunted with the posts mmi drew my attention to and this is where I take the bull by the horns and deal with VW and take all the information and advice You have all given and stand strong with confidence and grace...

 

[mmi]

Thanks for the update. If you haven’t seen this yet here is a general illustration of fuel system on 204PS vans. The nearest copy of full document can be found at forum’s download section The T6 2.0L TDi SSP-564


As Loz mentioned above there are two fuel pumps. One in the tank lifting fuel from the tank to engines high-pressure pump. The high-pressure pump is easily accessible, on front side of engine (more on the right side of vehicle) so the sound of that should be easy to isolate. But as in the picture the high pressure pump has a return flow back to fuel tank… hopefully someone is able to tell what kind of amount of fuel is expected to return to the tank… the return flow pressure indicated in the picture is very low anyway...

While waiting your update I run low in fuel and eventually refueled. Still I can’t make it slosh. Well, when almost empty doing a sudden stop – one quiet single slosh, yes. So I would like to say my tank has the baffles...

 

[Lady T]

Thank you so much again mmi...Excellent diagram, this gives so much clarity and I have taken the time to carefully process everything so that I can understand all the questions asked and the information that I have been endeavouring to give as answers.
This clears up your question Loz, thank you for your patience as you guide Me through focused questions...really appreciated
No 1 Issue...
Fuel Lift Pump No 1 on the diagram fixed within the Fuel Tank ( This is the Fuel pump VW Mechanic explained confusingly as the Delphi high pressure pump, VW Mechanic advised Me this is the part that is causing the issue of loud hissing/toilet cistern sounds confirmed by the VW Mechanic advising that this is amplified in sound compared to a normal sounding fuel pump/although he has never seen or worked on a fuel pump with the 204PS!) *Now I am clear in my understanding this is a Fuel lift pump, maintaining Fuel supply pressure 4.0-6.0?(VW showed Me a pressure recorded reading of 5.79/ this pressure reading was not clearly explained as being a fuel supply pressure or fuel return pressure from injectors)
Studying the diagram, the fuel return flow pressure 0-0.3 bar from the dual plunger high pressure pump back to the fuel tank is where You are highlighting the diagram indicated levels are low, am I clear with this understanding?
Dual plunger high pressure fuel pump No4 on diagram (I asked VW Mechanic to show Me every pump involved with the fuel system and this was shown to Me as You said right side front side engine although this was not explained as being a high pressure pumpVW said this was checked however return flow back to fuel tank explanation was not given)
This is extremely helpful information as this diagram has really given the detail within the whole picture, this has enabled Me to piece together all the information given and gather a greater understanding of the Fuel System... like a jigsaw puzzle... piece by piece... extremly difficult to put the pieces together without seeing the whole picture in detail on the front of the jigsaw box! I have been watching every diesel common rail fuel system and VW fuel system mechanical video on You Tube that I could find to understand every part involved!... this is valuable shared information and this simple diagram You have brought My attention to has clarified so much and helped Me have a far greater overall understanding. I am really grateful for all this information given by everyone, this enables Me to fully understanding the whole Fuel Injection System with 204PS, giving Me the confidence and knowledge to now pursue the Master Tech VW Sheffield and the all important experienced technical diagnosis regarding this Issue.
No 2 issue...
Sloshing fuel tank testing... excellent thank you mmi, You have really tested this baffles no baffles theory/story given by the VW Mechanic... I am still sloshing and I am between 3/4 and half a tank now... When I looked at the exterior shape of the fuel tank on this van, I saw that the tank was shaped with slight indentented grooved curves, this has in external appearance the design of a subtle curve/baffle, however I notice on the diagram you have shared that baffles within the fuel tank are not shown...
This ‘No Baffles’theory has the potential of being a bit of a VW Mechanic spin story #theory... the fuel sloshing about like a washing machine issue in this van is not answered clearly in any feesable explanation or has any evidence been provided by way of actual photographs taken from inside the fuel tank to prove this given #theory!
Thank you so much to everyone on T6 Forum, this is an incredible learning... vital information shared

 

[Loz]

So, I pulled up home yesterday after driving back from Milton Keynes and whilst letting things settle down at idle, I think I heared the washing machine, surging, wooshing sound.

I did some listening and experimenting and it might be caused by the aircon compressor.
As soon as I turned off the radio it was quite clear, then turned off the aircon (fan to zero turned it off completely) as it stopped.
Our aircon compressors are the variable pressure type so they are always running rather than disconnected.
So I wonder if that is what you are hearing as the aircon condenser is abover the passenger footwell and you could be hearing a surging of refrigeration gas through the condenser at idle?