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.