3BG AVF: Where does the oil come from?

Hi.

It's (still) not my car, so I can't do the usual cleaning-driving-looking around thing.

Where could the oil be coming from?
Does it look like an EGR membrane vent hole?!!!?

My understanding is that since the AGR is controlled by pressure, there shouldn't be any oil leakage from the diaphragm chamber.

The oil leak must therefore be coming from the LL (low-pressure) circuit. I don't know the internal structure, but somehow the EGR valve must be mechanically connected to the internal components. There seems to be a leak on the joint.

Alternatively, the shaft seal of the shut-off valve might be leaking, and the oil seepage could be pushed upwards through the round pipe by the airflow. However, I consider the latter option to be less likely.

Have you tried searching? I seem to recall a post about a drooling AGR.

Regards,
Guste.

If the bushing where the EGR valve operates is leaking or worn out, the boost pressure can bypass it and end up exactly where the ventilation holes open to the outside.

m;

Okay, then you probably just posted the answer to your own question .

No, a theory.

And I would like to have that either disproven or confirmed.

Unfortunately, I forgot to re-check my "AGR valve for future use" when I returned the G3, and then I didn't convert it from the bypass position .

You can hear the AGR valve clicking when diagnosing the actuator, so it's probably not completely broken.

m;

dieselmartin wrote:

no, a theory. And I would like to have that either disproven or confirmed.

*confirmed*

Ulf,

Do you perhaps have any recommendations or data on how much valuable boost pressure is typically lost?

The car has 126,000 km on the odometer, and it's possible that I'm the second person to have removed the engine cover (the first was the person who did the timing belt replacement, and they marked it amateurishly with nail polish).

m;

Hello,
From my perspective, the issue seems to be coming from the AGR valve itself, which is supplied with vacuum from above. It's quite possible that the diaphragm inside is damaged! When the AGR valve is open, the exhaust gases enter the intake manifold from below, right? Then you should see high air mass readings at low load and up to 3,000 RPM. Have you checked that? Of course, some unburned fuel could also be leaking through the AGR valve. If it looks like that after 126,000 kilometers, then the pressure is definitely in the single-digit mbar range.
The small side part is actually a valve (the parking valve?). Leakage through its shaft could also cause a loss of LLD (Low-Level Detection). But otherwise, the AGR (Abgasrückführung) part should be sealed. What do you mean by ventilation holes?
haithamina
EDIT: The image of an AGR valve linked here has been removed, as Martin sent two much better ones below.

The membrane is likely NOT broken.
Because you can hear the valve opening when the diagnosis "triggers" it, so it must have been pulled up beforehand. Even if the membrane were damaged, the spring inside would constantly press the valve shut.

Therefore, the only explanation is that the valve is still working, but it's leaking in the shaft towards the membrane.

Thank you for the link. But I'm suspicious of salespeople who don't know what they're selling.
The valve is mounted in a mirror-image configuration for both longitudinal and transverse installations. PD longitudinal motors draw air in from the clutch side, and transversely from the timing chain.

How can a longitudinal valve then be fitted to a Seat (other than an Alhambra)?

m;

Hi,
My only intention was to clarify the internal workings. Everything else is irrelevant to me. It's certain that the AGR valve piston is leaking at the top, as you already mentioned. More specifically, it's the connection between the vacuum sensor at the top and the tube below. No one knows how much leakage is occurring. The AGR valve will likely need to be completely replaced to resolve the issue.
I am unable to translate "haithamina" because it does not appear to be a word or phrase in the German language. It may be a misspelling, a proper noun, or a term from a specialized field. If you can provide more context or clarify the intended meaning, I would be happy to assist you with the translation.

Inside, it looks like this: (a cross-sectional diagram).

/download.php?id=1090

m;

Yes.
I understand, and that's why I removed the linked image from my original post. The two images are, of course, much better suited to illustrating the interior.
haithamina
EDIT: Do you know the air mass readings of the car? Should it fit?

No, so far only while stationary (idle and automatic scan).

m;

Quote:

Nobody knows exactly how much LD is released. You will likely need to completely replace the AGR valve to solve the problem

.

"Mine has been leaking for a while too, although probably not as severely. A loss of boost pressure probably won't be noticeable due to this 'sweating'." To be absolutely sure - which part should be "removed" or "replaced"?

I see this very often in almost all "unmaintained" TDI engine compartments! Even after 10,000 km, you'll barely notice any difference after an engine wash; it's only minimal, so don't worry about it!

dieselmartin wrote:

Do you perhaps have any recommendations or measurements of how much valuable boost pressure is lost in that situation.

That's all. Besides the reassurance that the leakage volume flow is likely to be so low that the LD (light detection) will not measurably decrease.
You could try opening the valve with a tool, while wiggling the piston rod, calculate the area of the leak gap, and compare the result with the other cross-sections in the intake manifold .