Fuel Injector Problems: Leak After Replacement

Hello fellow mechanics,

Actually, this was supposed to be a testimonial (a very positive one, even) about upgrading to 216 injectors, but things turned out differently. I'm really devastated right now...
The search didn't find anything comparable.

Last weekend, I replaced my nozzles, and everything went smoothly.
It started up immediately again, everything was sealed properly, everything was okay, and I was really impressed by the significant increase in performance.
Then I drove another 50 km, and everything was still sealed.
On Sunday, I drove 150 km on the highway. It ran perfectly, no smoke at all. I pushed it a bit, and the speedometer showed 205 km/h (instead of the previous 190 km/h).
On Monday, the big realization came. I was woken up in the morning, and while I was hammering, I heard something strange.
Noise, opened the hood, compression leak on the 2nd cylinder (from the left). It was hissing out, and everything around the cylinder head was very dirty. I bought a new gasket, cleaned everything, and tightened the injector nozzle with 25 Nm.
After that, everything was working perfectly again, but this morning, just for fun, I opened the oil filler cap, and now there's a significant amount of pressure inside (I think it's exhaust gases). The cap bounces when you put it on, and a little oil is spraying out.

Oil level is okay, and it didn't consume any oil during the trip.

He doesn't smoke, nor does he drink.

There is a diesel film on the exhaust.

Cooling water does not smell like exhaust fumes.

As far as I can tell, it seems to be working fine, and there's no loss of performance.

I fear the worst.

Warped cylinder head gasket?
Is Harris on your mind?
Tilted head?

I only saw something about the overpressure issue today, by chance. I last checked it a few thousand kilometers ago.

Before the turbocharger was replaced, the car generally ran very well. The only problem was an intermittent fluctuation in boost pressure at full throttle (overboost up to 1.3 bar, followed by boost pressure oscillating between 0.7 and 1.1 bar), which has been happening more frequently lately.

I hope this information is enough. I'm really devastated right now.

What do you think about this? What's going on with me?

Best regards,

kapernaum wrote:

In the morning, when I turned it on, I heard a strange noise while hammering. Noise, open the hood, compression leak on the 2nd cylinder (from the left). It was hissing out, and everything around the cylinder head was very dirty. I bought a new gasket, cleaned everything, and tightened the injector nozzle with 25 Nm.

Make sure to check if all the injectors are sealing properly, for example, by using motor oil that you inject with a syringe and needle into the gap between the injector and the cylinder head. Then, with the engine running, check for any bubbles that might indicate a leak.
"The specified torque of 25 Nm seems quite tight, in my opinion. I had to tighten it much more firmly on my AFN until no more bubbles appeared."

Quote:

It was running great after that, but this morning, just for fun, I opened the oil filler cap, and now there's a significant pressure buildup (I think it's exhaust gases). The cap bounces when you put it on, and some oil is spraying out.

IMO, there's no real cause for concern yet.
The "blower door" test on our ALH, which had approximately 30,000 km on the clock, yielded seemingly alarming results (the sheet of plastic rose almost to the top of the hood), but otherwise, the engine appears to be in top condition (fuel consumption, performance).

Quote:

I fear the worst: Warped cylinder head gasket? Is Harris on your mind? Head tilted?

There are definitely more obvious symptoms (like water in the oil or vice versa, etc.). I would wait for those and not worry about it (for now).

Does the lid fly off, or does it just bounce?

If it's just bouncing around in the LL (likely referring to a machine or engine), that's normal, and a little bit of oil spraying out isn't a big deal.
(From my experience, this is highly dependent on temperature and wear.)

Everything is a matter of definition, so a more detailed description would be helpful.

Otherwise, you did a great job with the jet tuning, right?

The AHU (Air Handling Unit) is not thermally designed for 216 nozzles, so I wouldn't want to overload it too much in the long run, otherwise the damage you mentioned will likely occur.

EDIT: Ulf was faster again.

Best regards, Georg.

Hello!
Thank you for the information/advice!

This morning, I was just overcome with panic because I know that he used to (I don't remember exactly when, but it was a while ago) not produce much... I was so shocked that I immediately had those unpleasant thoughts.
Currently, I am also writing my dissertation, which doesn't exactly reduce my stress or immediate panic .

I'll check later to see exactly how much he's blowing out, and I'll spray some oil on the injector nozzles.

The nozzle replacement itself wasn't really a problem. The ESP was immediately (with loose nuts) depressurized after about 3 seconds, and it ran normally even with a compression leak (except for the faint whistling sound).

Good evening.
Here I am again!

So, I tested it again (once with the motor cooled down, once at operating temperature).

So, the cover only bounces a little (it lifts about 0.5 cm from the valve cover, whether it's cold or warm), it's almost like it's 'dancing' on the valve cover...

The gas emissions are coming from all 4 burners (as far as I could tell, although it's only coming from one of them).
I performed the test using a DIN A4 sheet of paper, holding it against the valve cover gasket with a finger. It inflated to about 10-15 cm high (the paper had only a few oil splatters on it afterward). This morning, however, the situation was much more severe.

^^^This behavior is both warm and cold.

Thanks for the tip about using oil on the nozzle seat, Ulf!

The nozzle with the NHG is bubbling slightly at the cylinder head shaft, so tomorrow I will adjust the nozzle holder again by 30 degrees. Otherwise, I will also remove it again, clean the nozzle seat meticulously, and seal it again. If I had known this trick before, I could have slept more peacefully for one more night in my life.

The engine starts immediately on the first compression stroke, with no shaking or other issues.
During the cold start and while driving, there are no visible signs of excessive smoke, blue smoke, or white smoke.

I might do a compression test myself, or I might have Bosch measure the compression.

'I was actually there yesterday to have the screws tightened (my torque wrench is 150km away in my toolbox). The diesel mechanic wanted to send me to an engine rebuilder, saying the cylinder head was damaged and the injector seats would need to be re-bored (I didn't want to believe it, but I was still panicking afterwards).'

The sound insulation on the hood is covered in oil and soot, so I think I've been driving like this for some time (at least 75 km, driving quite fast on the highway).
'But the performance was there, as I said, he was really on fire.'

After reading both of your statements, I feel a bit more reassured (otherwise, I would have another sleepless night).

Best regards,

kapernaum wrote:

The nozzle with the NHG is slightly bubbling at the cylinder head shaft, therefore I will adjust the nozzle holder again by 30 degrees tomorrow. Otherwise, I will also remove it again, meticulously clean the nozzle seat again, and re-seal it.

Clean out the mounting hole in the rear panel with a cotton swab or something similar.
With prolonged leaks, exhaust gases can apparently create small, more or less radial channels in the aluminum, making it impossible to achieve a perfectly tight seal on the valve seat without further machining.

I once had a similar problem, and I built a "nozzle seat grinder." I glued a small piece of wet sandpaper onto the rounded head of a screw and used it to grind down the etched channels until they were no longer visible (and a thin screwdriver couldn't detect any "burrs" when gently pulled across them). Then, the nozzle sealed properly again, even with normal tightening torque.

@Rainer:
I actually wanted to include a photo of my "tools" as an attachment here, but the system says...

Quote:

You have reached your maximum upload quota limit of 5 MB

.
Could it possibly be related to the LDA photography article?
Is it possible to adjust the limit upwards?

Hi Ulf,

Actually, there is no limit per user, but the maximum size of a single image is 5MB.
Try uploading the image again as a JPG/PNG file with a lower resolution?
Raising the limits doesn't make sense to me. Imagine someone with a slow modem trying to view your image and having to wait for minutes until something happens...

Best regards, Rainer.

Rainer K. wrote:

Actually, there is no limit per user, but 5MB is the maximum size of a single image.

Well, it was about 270 kB just now, but I've managed to shrink it down to 107 kB.
And it still doesn't work -> the same error message appears again .

Edit: I'll email you the picture; maybe you can incorporate it.
But don't laugh out loud...

Edit 2: I just remembered that the abrasive cloth was probably more like a piece of wet sandpaper - but don't ask me about the grit now .

I'm curious to see what the Ulf-type grinding tool looks like .

kapernaum wrote:

I'm curious to see what the Ulf-style grinding tool looks like

Rainer parked it there for a while.

And what did you do with the sanding dust?

Hello Ulf,

That looks really interesting!

How did you attach the sandpaper (linen) to the tip of the screw?

'Since I'm planning to work on the second loose nozzle, I was wondering if you have any insider tips on how to best align and secure the nozzle holder so that the nozzle is as straight as possible.'

Best regards,

kapernaum wrote:

1) How did you attach the sandpaper (linen) to the tip of the screw?

With ordinary, everyday Pattex .

Quote:

2) Since I was planning to take care of the second loose nozzle, I wanted to ask if you have any secret tips on how to securely and accurately align the nozzle holder...

Wrap a thin strip of tape around the nozzle, at the height of the top edge of the nozzle opening.
Specifically, the nozzle should fit snugly into the hole, creating a tight seal.

Quote:

And what did you do with the sanding dust?

Wiped clean with a piece of oily cloth around a thin screwdriver.

The few tiny aluminum dust particles in the engine didn't bother me much. And the AFN (presumably a sensor or component) didn't seem to be affected either; it worked just like before.

Hey everyone,

Before I let the grime comfortably settle into the engine and sandblast the cylinders and turbo, I would rather drive a few kilometers so that the soot seals everything nicely on its own.

Regarding blow-by at the valve cover: Every engine (even a well-worn one) produces blow-by gases. The measurement methods mentioned have NO relevance. Why the concern if the car starts well and everything else seems normal? If a piston is damaged, you will definitely notice it in other ways .

Best regards,

Albrecht.

Albrecht wrote:

Instead of letting the grime slowly seep into the engine and having the cylinders and turbo sandblasted, I would rather drive a few kilometers so that the soot seals everything nicely on its own.

Tsts... Dust from ~600 grit sandpaper definitely doesn't have the qualities of sandblasting material for me.

And if the soot were sealing the nozzle seat properly, after replacing the nozzle, I shouldn't have seen any bubbles in the oil sample after driving several hundred kilometers...

Good evening!

Okay, I just wanted to give you a quick update. Today, I removed the nozzle again, cleaned everything thoroughly, and reinstalled it with a new sealing ring. Everything seems to be tight now. The old copper sealing rings were quite interesting due to the leaks; they were already noticeably red-yellow and corroded after less than 200 km (the color suggested sulfur). After several tests with oil sprayed onto the sealing surface, it seems everything is tight. I don't think the engine has suffered any damage... (Except that it's now as oily as an old ship diesel. )

*Knock on wood*

I will be keeping a close eye on you now...

Thank you again for the great advice, it's really excellent!

In a few hundred kilometers, I'll post a detailed report about my experience with replacing the injectors on the AHU forum.

If my laptop cooperates, I'm going to reduce the idle speed by about 40 RPM, and then I'll use VAG Com to log my air and injection values soon, because of my turbocharger problem.

Best regards,

P.S. I only replaced the injector nozzles, meaning the opening pressures haven't changed. Do I need to adjust the injection timing somehow with the larger nozzles (because of the now increased fuel volume in the cylinder)? Could adjusting the timing perhaps make the combustion process 'smoother'? (Sorry, I can't express myself more technically).