Diesel return pipes

they are leakoff pipes, excess diesel returns back to the tank eventually, most are routed through the fuel filter.

you reslly don't want a leak here as it'll make a mess, and when left standing will suck air back into the system making cold starts a curse word.


not sure what arrangement your particular engine has, but if they are the old mechanical type injector with a barb each side then do make sure you get decent rubber 3mm fuel resistant hose, do not use the generic 1/8" cloth overbraided curse word that is everywhere, as that translates to 3.2mm and doesn't fit tight enough.

for my bmw tds I went to a citroen dealer and bought a metre length for under a tenner, as bmw wanted £30.

for the same bloody stuff.

if its a later commonrail type injector where a small clip secures an o-ringed plastic fitting into the top of them, then it'll be oem only if you've broken them.

its basically just any excess diesel that bleeds off, I'm not certain of the exact details of how it works in a commonrail engine.

diesel lubricates the moving parts of the injector, with the old mechanical injectors there is still a little pressure in the feed lines after the needle has settled back onto its seat as the pressure drops when the cam plate rolls over to the next cylinder.

Yes, I thought the seal was stuck in the head so I refitted the injector to start the car to give the seal some heat but I’m not convinced now.

These injectors don’t have a consistent bore from the valve cover to their finish in the cylinder head, there is no bore from the top of the head to the top of the valve cover, real poor design. I now fear the seal dropped into the valve area while I carefully withdrew it through the valve cover, that or I was really unlucky and the seal broke and left no trace when I removed the injector and all parts fell into the cylinder - I don’t think this was the case as there was no twisting to remove the injector just a direct pull out.

I’ve had a bit of a nightmare with it if I’m honest. Never had this trouble before.

I hope so mate, preferably still at the bottom of the cylinder bore and the grove screw on my reaming tool is stopping it hitting the bottom of the bore and causing my confusion

This is on an Audi 3.0 v6 if that helps at all.

I’ve taken a couple of pics today

Bore 1, the one I’m having issues with



Bore 2, which came out with the sealing ring on it



To me there is still a sealing ring on the base of bore 1. What do you think?

I’m not sure, someone has been here before me as the bolt that holds the injector in was loose but not loose.

Can you get repair shins and that’s what I’m looking at?

That’s my concern, everything shows copper seals.

I emailed a mobile injector removal guy and he said it looks to have a seal present but possibly an aluminium one or aluminium coated and may have sealed itself to the head. I don’t want to keep going at it incase i am going at the head instead.

I’m really stuck now, my cutting tools aren’t cutting fully on the face of the washer/head, only the centre or the external edges making me think it’s still got a seal present.