DPF wash out and rebuild

[Diesel_vert]

Could just be a dodgy exhaust pressure sensor (G450 if I recall correctly), though you might have already replaced it?

[poyta]

So in hindsight when buying a second hand diesel car with DPF should use diagnostic equipment to check out clogging to avoid a time bomb OR go for GTI ( non DPF) not GT as fuel consumption and torque is improving eg MK7 GTI

You cannot compare a GT to a GTI, two completely different cars with completely different engines. You are right though that a buyer needs to do some investigation when buying a modern Diesel as most if not all of them now have a DPF so eventually all of them will have issues for potential buyers with clogging - having said that its not like there's no issues with a modern Petrol either , the GTi has a lot of common problems for potential buyers too - the important part is that there are solutions to the problem. The washout you performed seems to have worked for Greg, the Moly treatment did wonders for me and for others a DPF delete has been highly successful but remember that a DPF delete is illegal and comes with some very heft fines if caught so if you do go down that path my suggestion is keep it to yourself and don't go posting it on the forums.

[Harpo]

G450 sensor checked by VW once and Euro specialist 4 times. VW quoted approximately $4800 for DPF replacement and install.

[Greg Roles]

OK so my DPF filled up a second time at 200 thou, and it went a lot more quickly than last time in the final stages. Whereas I had a long lead up of increasingly more numerous regens the first time, right down to every 50kms, this second time the car went from doing regens about every 100kms and suddenly tried to do three forced regens in a row ( 50 plus kms of regenning!! ) and went into proper limp.

So I did the old cut and shut a second time, in one day. It's a bitch to remove on a simple jack as you need to wriggle it around and the long tail pipe makes that difficult with limited height, but would be a piece of cake ( comparatively ) on a hoist.



I had no idea how successful this would be second time around, but unlike last time I was on a schedule ( needed the car the next day ) so I didn't bake the core in an oven to get the water out like last time. As such, despite leaving it in the sun and wrapping it in absorbant towels for a good few hours, it was likely still wet. I welded it up, banged it back in, and low and behold car was still going into bloody limp despite any form of reset.

Oh crap. I put my old G450 differential pressure sensor back in thinking that may have been it, but ended up deciding I had to limp it up to VW the next morning to try a new G450. On the way, at a very slow limp speed, it must have cleared the water, and it suddenly decided all was good, and the car reset to zero ash and has been there quite happily for 5 thou now, running like a champion. It always starts off doing regens about every 200kms, but this has been increasing up to 300kms now, as the G450 kind of relearns, so expect frequent regens for the first several or more, always seems to take a bit of time.

SO the moral of the story is if you backflush the core, make sure it is dried out properly, as this will provide the G450 with enough pressure difference to think it's still clogged, well that seems like the situation to me anyway.

[Mysticality]

... Or do a half assed job of drying it out then let it run in the back yard/around the block for awhile!

[Greg Roles]

....which if the G450 sees over 80-90% blockage will not let the car start. I dried mine out quite well ( I thought ) but it was still obviously beyond a 60% reading where the car wants to stay in limp. Slippery slope, bake it in the oven when the missus is out.

[kaanage]

Or put it on the Weber

[benough]

My GT TDI is now at 230,000km and the DPF is still behaving normally.

[Greg Roles]

You Sir are what they label an "anomoly" on a bell shaped curve. Even my Yeti running two Provents is showing towards half full of ash at 70,000kms and I'd expect it to clog about 150kms as is usual.

[jets]

My GT TDI is now at 230,000km and the DPF is still behaving normally.

That's good news for the rest of us with lower mileage cars with a DPF. Do you do a lot of highway kms?