DPF wash out and rebuild

[Greg Roles]

I don't support DPF deletes, and am quite sure this is Viezu's official stance nation wide. Very illegal, obvious, and makes your car spew soot like a bus. Not cool.

[AlexRO]

Yeah i completely understand that side of things, I didnt want to go straight pipe, not a fan of soot flying out either. I wanted to come in half way between straight and dpf to get the best of both worlds. May have to keep looking around.

[poyta]

Instead of cutting it right out like I did, I would suggest cutting outside the top and bottom canister welds, as you can leave the core wrapped in the steel can. There is a support shelf at each weld to keep the SiC core in place, so cut above and below the welds by a cm or so to just remove the ends. Go to town with a pressure washer and wash against exhaust flow.

Any chance you could send a photo showing the ideal cutline? Also by keeping the steel surround does it not also mean that you will be leaving the heat sheild around the core? I imagine that this would get seriously soaked during the wash out and the chances of it drying out are pretty slim?

[noone]

Great info, the DPF is one of the main reasons I'd thought I'd never buy a VW with DPF filter (well, the huge costs to replace).

Greg, do you think you would ever offer a swap-service (send me your clogged one, I'll send you a clean one)?

[Greg Roles]

I'm not really interested in washing out cores as it's quite a task and my time is limited, much more interested in perfecting the sports DPF idea which replaces the whole problem entirely. It really is a DIY if you plan it out. I will add a better DIY washout article too, both going up on my site this weekend, as I get a LOT of these questions......

Poyta the DPF hits 700-800 degrees during a regen, and water turns to steam at 100 so it's not going to stick around. Normal DPF temps are 100-400 degrees anyway : )

[Greg Roles]

Here are the pictures I will use for my writeup. On reflection, I think just cutting open the BOTTOM, to expose the full face of the core, to back blast it with a decent pressure washer will be the go, no real need to cut off the top as well. You do need access to the full lower face though to do it properly in my opinion, given the near HOUR I spent with a Karcher 2.54 on full power right up against the back of the core. I tried to see if it was possible to erode the core with the washer, and on my Karcher at least it had ZERO effect. I didn't go stupid though, and ten minutes on one spot "could" erode the surface, so common sense please!

I am sure people doing pressure backflushes get a good effect too, but they sure must use serious flow / pressure!!

The "shelf" that holds Silicon Carbide cores used in VAG vehicles is at the level of weld, as shown by the following pictures. The top section is 1-2mm thick stainless and VERY hard, given it must survive direct turbo outlet temps. The bottom section is MUCH softer.

Cut it open with a 1mm or thinner cutting blade, you need as thin a cut as possible to assist welding it back up. Don't use a grinding blade!!! If you have Oxy etc, then go nuts.

Is a good idea to do an exploratory drill hole, just to find the bottom of the "shelf". If you cut on the lower side surface, about a cm below the weld line, you are very safe, towards the curved bottom edge is a great goal. There is nothing in there to damage, and the stock outlet is pathetically tiny, so don't worry about it. May be different in bigger diesels, the pics below are for the Golf / Passat only in MK V / VI as the bum of the canister is similar in both.

This is my modified high flow DPF canister, and NO it's not proven as yet. It needs to meet emissions, as there is zero future in polluting technologies. Quite a challenge, but I think do-able in Euro V at least.

[Greg Roles]

Also, looking from the back end ( outlet ) of the DPF core, you will see a checker pattern. The open pores are the OUTLET holes, and there is no soot in them, they are basically a cup "facing" out". All the soot is trapped in the alternate "closed" cells, and they are basically cups facing forwards. These closed channels are the ones you want to back blast, but so too forcing water up the open channels will only aid that process.

Just don't make the mistake of focusing on the holes, when you really need to focus on the closed squares.




If you look closely at that pic you can see the soot actually trapped in the edge "outlet" holes that have been resting on the lower "shelf". It's that white ash that is the enemy, and which you need to remove. Nothing, no additive or extended regen can get rid of that oil based ash. A commercial kiln at a few thousand degrees yeah probably......

[poyta]

Thanks Greg. I'll have to give it a go and see how it goes. Can you advise if you need to get the car up on a hoist in order to remove the DPF or would it be possible if I could get the front up on some ramps or stands?

[Ideo]

Great info, the DPF is one of the main reasons I'd thought I'd never buy a VW with DPF filter (well, the huge costs to replace).

Greg, do you think you would ever offer a swap-service (send me your clogged one, I'll send you a clean one)?

You mean any modern diesel? DPF and the huge costs associated with replacement is common to all diesels.

[noone]

Well, probably mate, but I can't see a Jap DPF being 3-4K to replace...

[Ideo]

Well, probably mate, but I can't see a Jap DPF being 3-4K to replace...

I've seen a 8k quote on a Mazda 3 Diesel...

[Greg Roles]

Yeah the Mazda's have a whole extra level of complexity, and I'm only just getting my head around it now. They are a NIGHTMARE compared to the SiC Vag and most Euro cars use, but clever in some ways too. Absolute bitches when they go wrong from what I have been reading.

Yep Poyta I did my whole thing on ramps, but you do need to drop the drivers driveshaft, or at least wriggle it out of the way to get the DPF out, and it has female torx bolts. You need to plan the task ahead of time, and allow a good weekend to do it, the DPF comes out fine, but it's a bit of a chinese puzzle the first time out. Be very gentle with the sensors, easy to upset them. You need to soak them in WD40 for a while before trying to undo them, they can be bloody tight.

Expect skinned knuckles!!

[poyta]

Greg, can you give us some specs the the pressure washer you used? I have a cheapie pressure cleaner but not sure if its ample enough to do the job.

[Greg Roles]

Karcher 2.54 with three pressure settings, I used it on flat out. It's an old model now - but has a max 100bar pressure at 400 litres an hour. They are going to be dead cheap this Queens Birthday weekend at Supercheap I reckon!!

[Harpo]

I have just bought a lovely MK5 GT diesel with only 60K on the clock and the DPF is stuffed.
Have had performed numerous forced regens and completey remove DPF and soaked in moly cleaning fluid over night worked OK for 200 klm intervals for a while and then limp mode. Approx cost so far $1300.
... anyway Greg is your squiky clean DPF still going good?