Hi all,

 

Giving something back today.  Please note, this is purely my experience and point of view regarding used vs new parts etc. Make up your own mind. I appreciate others may have had slightly different experiences.

 

I was recently looking around here, and also various VW and Audi forums, to try and get a handle on an issue I was having (see pic). There was a lot of the usual opinion, some accurate, some not so, and as it seems to be such a common occurrence I thought I'd add what I've had done to sort it.

 

The pic is looking down at the Ad-blue injector on my 2017 Superb 190 Diesel estate DSG.  You're looking at Ad-Ble that has escaped under pressure.  The warning on the dash is "Reductant pressure too low" (P20E800 code). There was also a message to say ad-blue was running low and the car would go into limp mode in 650 miles.

 

The first thing that I have realised, although it's not always, just often, is that this issue seems to have been posted by others during the coldest winter months. It happened to me the day after the temperature dropped to -8 degrees.  I thought it was frozen water [snow] at first as it looks like it but it wasn't cold. It was solid though and chipped off easily. Hot water then cleans it off perfectly.

 

I cleaned it, cleared the fault code, topped the ad-blue up, and drove carefully to see if I could detect the leak.

 

It seemed ok for a few days but then returned so I consulted a VW mechanic I know. He confirmed it's very common across the group brands on this engine. He also tried to convince me to delete the ad-blue system but that's a different post.

 

He confirmed the failed parts (04L131113P - Injector and 3Q0131984N - Pipe) and explained why they both needed replacing together. Apparently, DIY'ers miss this sometimes and end up buying injectors twice. The pipe is damaged/blocked and the pressure build-up can damage the injector. You can see how the ad-blue solidifies.

 

He also dissuaded me from buying used parts. There were some available on ebay but for the difference in price, it isn't worth not knowing if they've previously had this fault and been cleaned. New parts also come with a warranty.

 

I managed to source an injector, brand new, for £158 delivered. He had to source the pipe which was £255 delivered inc VAT.

 

Here's where it gets interesting. I'm handy enough to tackle many jobs. After watching him doing it there's no way I'd have been able to.  The pipe is fed through a very very tight aperture at the base/back of the engine below the injector. It then runs down through the chassis popping out along with the fuel line at the rear. It's a cramped space and circa 10 ft to feed. The pipe has attachments at either end that make it harder and it's incredibly fragile. Also, there are small wires, a connector, and the fittings that can all be damaged very easily. He knows what he's doing and it still took several hours.

 

The injector itself was somewhat easier but still fiddly.

 

So. There you have it. If you have this issue, you know what needs doing. If you can find a mechanic that will let you source the new parts then there's a few hundred pounds to be saved. Expect up to three hours labour at worst. Possibly two if it goes through easily without snagging. There's no access point to prevent that though.

 

This was done several days ago and it's running well again with no issues.

 

Feel free to message with any questions.  I hope it is useful for someone.

 

 

 

16 hours ago, IndeedFox said:

The pipe is damaged/blocked and the pressure build-up can damage the injector. You can see how the ad-blue solidifies.

I do love a good bit of mechanic bull****tery… what he is actually saying - he can’t work out exactly if it’s the injector or pipe leaking so he’s going to replace both - and he’s somewhat right, it’s really hard to tell which part the leak is coming from as it’s all covered in plastic

 

If the pipe was blocked the pressure build up would be before the injector, it also can’t over pressure the injector as a restriction would drop pressure at the injector and the maximum pressure is maintained by the pump in the tank.

How could we prevent this from happening? Is it low quality AdBlue? Where I live OEM AdBlue retails for 35-40EUR/10L. I cannot justify that and buy Polish Hico for 12EUR/10L from a renowned dealer.

I use Redex AdBlu, which is about £15-£20 for 10 litres bought locally and I've never had any problems with it.  If the AdBlu is ISO 22241 which the Redex is, I assume it should be OK?  I've not seen Hico for sale in the UK, but looking online it says it's ISO 22241 compliant.

 

Edited as text was different sizes.

Edited 6 February, 20242 yr by Penpusher

From what I gather, Its little to do with the quality of ad-blue.  One of the clankys at the Skoda garage actually quipped that they wish that they didn't have the system on at all. I get the impression its something that causes more issues than they let on.

Yes, label says it is 22241 compliant. I was warned of usage of  passed expired/best before date might cause flaking and a residue that might clog the system. If anyone has any feedback, more than appreciated. Cheers.

10 minutes ago, Penpusher said:

ISO 22241

Yes, label says it is 22241 compliant. I was warned of usage of  passed expired/best before date might cause flaking and a residue that might clog the system. If anyone has any feedback, more than appreciated. Cheers.
 

2 minutes ago, IndeedFox said:

they wish that they didn't have the system on at all

Strangely enough, a lucky friend of mine has a Koleos MY19 with no AdBlu from the factory. In PSA cars they had a common ventilation valve/cap problem which corrupted the whole system. I don’t mind pouring some every 4-5kkm as long as doesn’t fail.

In terms of the mechanic bu***** , I think it's maybe, as you say, them being sure.  I took it to Skoda who told me that it definitely needed both the pipe and the injector because once air gets into the system, it solidifies.  Interestingly, where I had it repaired is a friend's garage and he wasn't charging me for the labour, so there was nothing in it for him.  He did confirm what the Skoda garage said and said that he's had many jobs in where an enthusiastic DIYer has changed the injector alone and then the pressure from the damaged pipe has caused it to go again.  I had a look at both parts as they came off and the pipe was clearly solid in feel along a number of places whereas the new pipe was freemoving all along its length. The injector was £158 so it wasn't worth risking having to do it all over again. For someone who is actually paying for labour, that's way too big a risk. 

 

It's just my particular experience and it was my decision on the job and the risk. I can guarantee that it's now running fine so I have peace of mind.