Hi,

I recently developed a chuffing noise and black gunk above my exhaust manifold on the passenger side bank, after a bit of a search on here I found it was the injector seals rather than the manifold gasket. I replaced the copper washers on all 3 injectors on that bank, they were the worst I've ever seen to be honest. Practically non existent in the middle cylinder. I cleaned the bore, seat and injector as best I could and refit with all new seals. This lasted a couple of weeks before the chuffing noise reappeared. It was the middle cylinder again. Replaced the washer again, though it didn't look very badly worn, I believe I may have fit it upside down (chamfered face towards the injector body) so this time I fit it with the flat side against the injector and the chamfered side down in the head. This was around 3 weeks ago. I've just got in my car tonight and it's chuffing again!! I haven't removed the cover yet but I popped the bonnet and it's definitely the passenger side bank again.

Any ideas why I'm having such issues? Is this an injector fault? Or are the seals I bought off ebay no good?
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All ideas welcome. Thanks in advance

 

Sounds like you didn't use OEM seals, I'd start there. After that, you may want to look into re-cutting the injector seats.

 

I didn't use OEM seals. I got them off ebay. I'll head to TPS Monday and get a new set. If it happens again I'll get the seat recut, however the fact it seals for a few weeks makes me think it's more likely the cheap seals

 

You neglected to mention what year your engine is. Definitely I would be using either the factory OE/or the OEM copper seals rather than some other 3rd party alternative. Likely more important though is the torque value/ hardware you used to secure the injectors with. Before you fit new seals to it, those seats have to be spotless, with no residual debris from the old copper seals or carbon/soot deposits, etc., as requires a pristine sealing surface.

If it's the Gen 2 TDI (2013-2015 Model Years Q7 in North America), then the single (stretch bolt) injector fastener that holds tension on it has to be replaced each time it is removed, as those bolts are designed to deform slightly when torqued properly, so they cannot be reused...they will not provide the correct torque value and are at high risk to break off if reused when torqued using the factory spec of low torque value + an added, specific turn radius value.

If you have the earlier, Gen 1 TDI engine, then you have to pay close attention to the metal bracket orientation (that holds/secures the injector body), as well as getting the two small, hold-down nuts torqued correctly, etc., and there is guidance procedure on how to do it properly. Don't drop those nuts!

 

Sorry I forgot to mention that part. It sounds like it's the gen 2 engine with a single stretch bolt, though the car is 2012 MY. I did buy a full fitting kit with new stretch bolts. They were torqued to 6nM + 90°. As I said though, this was an ebay kit. So probably not very good quality. I'll buy genuine and try again

 

Just as a word of caution, be sure that it is actually the bypass port that is 'chuffing' at you. After I did the injectors on mine, I started smelling exhaust/hearing a little bit of noise underhood again, but now it is coming from either the EGR tube @ turbo, or it's the rear turbo gasket for the exhaust. Haven't zeroed in on which one it is on mine yet, but it's annoying! Audi swapped out the turbo and the EGR in the car during warranty, so they've had their little goober hands on everything that could be leaking now....figures.

 

Thanks for all advice so far. Just wondering if this could be an injector fault? The first time I changed the washer, the injector bolt was loose and the washer was almost non existent! Is it possible that the injector no longer reaches as far down the bore as it used to, so the copper washer isn't being compressed enough?

 

Probably not.
If you notice the design, the copper washer abuts the body surface of the injector, and the spray tip simply passes through the washer and goes down into the cylinder head, so really, the only common failure points are the stretch bolt being reused, which results in correct torque not being achieved (or shearing the bolt off), etc. If your prior seals had failed, it's also important you clean up the mating surface on the injector body, where the new seal fits up against, etc. Beside the stretch bolt, I guess the holding bracket that fits to the injector could be suspect, as that's the only other piece of hardware linked to holding the injector in place properly.

As noted prior, when you shine a good light down the bore for that injector, the seat area needs to be spotless, so the prep to clean that and the injector body's mating surface is extremely important prior to reassembly, as is using new seals that are the correct dimensions/thickness required for this engine.

You don't have a ton of mileage on this engine at 164k Kilometers (101k + miles), so it is doubtful there is an injector 'problem' per se, but you should definitely take any/every opportunity when the injector(s) are removed to examine them for failed oil control O-ring and/or copper pressure seal, etc., as well as closely observe the spray tip for carbonization build-up and or the spray tip 'mushrooming'. You will want to clean the carbon deposits up close to the body/seal area too, but the spray tip expanding towards the end of it is a sign of damage to the injector, etc.

I'd also suggest you be proactive in changing the seals/inspecting the bank 1 side group of injectors, as well, since you said all three copper washers were eaten up on the bank 2 side. Those seals and the oil control O-rings do get consumed and/or fail over time, while the injectors themselves can last from 120k miles to 180k miles if taken care of, so when you see consistent wear on one bank of cylinders, then expect to find the same on the other bank of cylinders. The injectors are fairly expensive part to buy, so it's a lot easier/cheaper just to maintain their seals proactively.

As far as on-the-car diagnostics, you need a Ross-Tech VCDS VAGCOM or similarly capable VAGCOM to really be able to diagnose this car well, but other scan tools may offer some basic live-data feeds also, where you can go look at the injectors balance/fueling to see if you have any outliers when the car is running, etc.

FWIW:
As soon as we bought our used Q7 TDIs (both had approx 90k miles on them), we performed a 'maintenance reset' and changed all the filters/fluids/lubricants on them, serviced all driveline lubricants (front/rear diffs, xfer case, transmission) as well as using a strong injector cleaner (Liqui Moly additives used), and I use the same injector cleaner during my annual maintenance on car (includes a new fuel filter), while using a Hotshot's EDT diesel fuel supplement product to raise Cetane values, protect the HPFP (adds lubricity), and keep the fuel system maintained/protected the rest of the year. The side benefit of this is the engine runs extremely strong and gets increased fuel economy too, while reducing fueling system problems/failures over the longer term.