AGR Valve Cleaning: Common Issues & Solutions

Hello,

The strength of deposits formed by oil sludge, soot, and AGU (Anti-Grinding) can apparently vary significantly from engine to engine.
It might initially be related to the driving profile: The higher the proportion of high engine load, the less frequently the EGR valve is open, and the cleaner the intake manifold needs to be.

It's quite surprising that even PD (direct injection) engines, which are supposedly almost perfect in terms of atomization and therefore produce very little soot, sometimes have thick layers of carbon buildup in the exhaust manifold (example: see the appendix, I "borrowed" the photo from https://community.dieselschrauber.org/en/viewtopic.php?t=6107 -> I hope Ecki doesn't mind).
Initially, I suspected that these variations were not due to design flaws, but rather that the EGR valve was not closing properly in the affected engines.
As long as the "incorrect opening" is small enough that the excess air in the cylinders is still sufficient for acceptable combustion even under high load, I don't believe there will be a noticeable loss of power. In other words, in everyday driving, you will practically not notice anything – especially if the problem gradually worsens.

But how could the increased soot from the "richer" combustion then re-enter the intake manifold? When the engine is under high load, air flows from the intake manifold into the exhaust system, and this air should prevent the exhaust gases and soot from flowing back!

In a normally functioning EGR system, the valve is likely to be more open than the small amount it would be open if it were stuck in the open position. This means that the amount of soot in the intake manifold would not be higher than in a system with a properly functioning EGR valve.

Or are there common operating conditions where the EGR should already be closed, even though the pressure conditions still allow the correct flow direction (exhaust -> intake side)?
That would mean giving up the AGR component and unnecessarily increasing the NOx content in the exhaust.
Then, a partially closed EGR valve would naturally cause more exhaust gases to enter the intake manifold, which would result in more soot.

Or can thick layers of sludge in the intake manifold occur without simultaneous full-load soot production due to a malfunction of the EGR system, but only due to increased soot formation during combustion, e.g., due to defective/worn injectors, so that the normal EGR function also causes more sludge to build up on the intake side?

Please help, I'm a little confused .

Hi! Regarding the soot content, I believe it's not the full-load portion of the driving cycle that's responsible, but rather the absolute number of hours spent operating under partial load. In other words, a clogged intake manifold won't be 'cleaned out' by full-load driving, unlike the analogy with two-stroke exhaust systems.

And then, of course, the driving cycle immediately after a cold start is particularly important. Those who have to wait at many traffic lights directly after starting the engine in cold winter conditions will likely experience a rapid buildup of deposits, especially since all the parts of the intake system are cold, causing a lot of condensation.

Regards,
Holger.

Hi,

In about a quarter of a year, we'll know more... that's when I'll be doing my 45,000 km service, and I actually want to take the intake manifold apart. It will have been operating with the EGR system for 45,000 km and will have seen a lot of city driving (cold starts, 10 km trips, lots of traffic lights). I'm very curious to see what I'll find.

Of course, there will be a comprehensive photo documentation.

Best regards,

Jan.

'I only have one V-belt, but my intake manifold was still very verschandeln at 150,000 km because I spent 85% of my driving time in the left lane of the highway!'

Here's another horror picture! It's from the Passat3b.de forum!

Based on the shape of the intake manifold, it appears to be a port design.

http://img15.

/img15/9633/Manifold.jpg

Regards,

Manuel.

SeatArosa1.7SDI wrote:

Hi! Regarding the soot content, I believe it's not the full-load portion of the driving cycle that's responsible, but rather the absolute number of hours spent operating at partial load. In other words, a clogged intake manifold won't be "cleaned out" by full-load driving, just like in the case of 2-stroke exhaust systems.

Hi Holger,

That's not what I meant at all.
I was referring to the percentage of time the engine is running at full load (or high load with the EGR valve fully closed) over the entire engine operating time.

For example, when the EGR valve is closed 80% of the time, there isn't as much opportunity to create soot as there is when the engine is at 80% load with the EGR valve active.

@Manuel:
Do you have a link to the topic that your image is about?

http://www.passat3b.de/phpBB2/viewtopic.php?t=17146


Regards,

Manuel.

Manuel Thomas wrote:

http://www.passat3b.de/phpBB2/viewtopic.php?t=17146

Wow, there are even more scary images in here.
And so many drivers claim that their intake manifolds are clogged -> it seems there are practically no engines with active EGR and verschandeln intake manifolds (after a certain amount of mileage).

EDIT:
I immediately saved those beautiful photos and included a few of them in the AGR article.
Thank you again for the link .

Hello!

Based on my experience, the amount of sludge buildup in the AGR system can be viewed similarly to oil consumption. The higher the oil consumption, the more sludge buildup.
Das Fahrprofil ist sicherlich auch recht wichtig. Hierzu kann man aber bei Longlife Modellen den Rußeintrag auslesen und dann Rückschlüsse auf die AGR-Versumpfung ziehen; als Anhaltspunkt. IdSure, here's the translation:

'ee?'

I also find it interesting that the VEPs (visual evoked potentials) seem to be more affected than the PDEs (pattern electroretinograms). I don't know yet whether this is due to the PD oil being somewhat thinner in consistency, but my observations currently confirm this.