High Oil Consumption: Causes & Solutions

Okay, so...

I have a '91 Passat TD with the engine code AAZ and a very high oil consumption of about 1 liter per 100 km (I have NOT made a mistake). The engine has already been to the workshop because of this problem (they showed me an error code, and they said it was the turbocharger ).

Since I was fed up with the problem, I just replaced the piston rings, valve stem seals, and the turbo (and a few other things). Despite that, it's still consuming excessive amounts of oil. The intake area in front of the turbo is completely coated in oil, meaning it's sucking oil from the engine's crankcase ventilation system through the turbo and burning it (resulting in blue smoke when driving). I've done everything I possibly could, and I have no idea what else it could be. So, here are my questions:

What's causing my engine to consume so much oil? What else could be the reason why the turbocharger is sucking in oil instead of air from the (new) air filter?

Thank you.
Fredwurst.

Hi, I have to keep things general because I don't know your engine: The problem of oil mist or spray being sucked in is present in all engines. Therefore, there is either a baffle plate or a labyrinth structure in the area where the blow-by gases escape (cylinder head or engine block), or an oil separator in the ventilation line with a hose that returns the oil to the oil pan. You should check these parts.
Perhaps you have a problem with one of the injection nozzles for piston cooling or another oil line, causing oil to spray directly onto the ventilation connection.

Hello,

Have you done a compression test yet? If there's a crack in the piston, new rings won't help much.
Don't hit me now and don't say, "I should have noticed when changing the rings!"
Given such high oil consumption, one would generally expect to see larger differences between the cylinders when performing a compression test.

Best regards, Rainer.

Hello (and thank you for your help).

The pistons are fine, and the compression is evenly distributed across all cylinders (as it was before). The pistons themselves look very good (I've never seen used pistons in such good condition...). I'm simply ruling out this issue for now.

The issue with the piston cooling is something else worth considering. I took a closer look at this on another engine block, and it might be the key to understanding the problem.

The story about the oil separator is also interesting. Since I've never seen an engine like this before, the question is how and where such a device could be located. My engine's ventilation system runs from a fitting (next to the oil filter fitting) with a plastic hose/pipe to the ventilation outlet on the cylinder head cover. From there, it connects to the intake hose of the turbocharger. It's possible that the 'specialist workshop' forgot to install it (they've messed up other things on this engine as well, so it's not beyond them).
So, the question is: What should it look like? Which parts actually belong to this engine?

In a documentary /viewtopic.php?t=1271&highlight=%F6lverbrauch+ventil, there's a tip about a faulty leaf spring valve. This is new to me. The question arises: do AFB/AKN engines have the same component as AAZ engines?


I would appreciate any further tips.
Fredwurst.

Hello,

For the AAZ engine, the ventilation should be configured as follows:

- On the cylinder head, next to the oil filler cap, is the pressure regulating valve (made of plastic with two connections).
- One connection goes downwards into the cylinder block.
- The other one goes to the intake hose.
- The pressure regulating valve itself is connected to the cylinder head via a rubber piece.

Hi and thank you.

I've just taken another, closer look at everything. There's a T-connector between the intake hose (air filter box/turbocharger). This connector holds a piece of plastic tubing (just a piece of plastic pipe with two male ends). Another pipe is attached to this, leading to the pressure control valve (cylinder head cover). This is held in place in the cover with a rubber sleeve. Another connection runs down from there via a pipe and ends in a 90-degree bend, which is screwed onto the engine block next to the oil filter housing.

As Michael II already mentioned: The path from the intake hose to the pressure control valve (just a plastic container) is the same. That's the normal, typical VW way...

OK. Another question...
The plastic piece described above, which is located in the T-junction of the intake manifold, should perhaps be replaced with a reducer/valve instead?

Hello,

To the best of my knowledge, that's just a plastic sleeve. Nothing more.