Oil Leak: Increasing Amount, More Loss - Dangerous!

As I described in my previous question about engine cleaning ( https://community.dieselschrauber.org/en/viewtopic.php?p=24042 7), my Passat (B6/C3 from 2006) has a problem with oil leakage (see also the photos below).

The oil level is above the maximum mark (i.e., above the upper "hump"), which is causing me great concern because, as far as I understand, it means that the oil is being dangerously diluted by something (e.g., diesel fuel due to post-injection during regeneration?).

I noticed this a few weeks ago. I'm actually ruling out the possibility that too much oil was added during the last oil change (which was about a year ago and done by an independent workshop), because I check the oil level before longer trips, and I would have noticed it then.

I also noticed it, but only in November, and I haven't driven long distances since then. I wanted to take care of it earlier, but it's been delayed. Although I know that too high an oil level isn't good for the engine.

Overfilling is relatively unlikely for several reasons: the oil used was from original Castrol 5-liter containers (Longlife, with the correct VW 507 00 specification), and I still have the remaining oil (although it wasn't precisely checked). Of course, it's possible that not all the oil was drained, but that is also unlikely (see the reasons mentioned above).

Also wurde/wird das Öl mehr und gleichzeitig ist (deswegen?) etwas undicht und tritt aus. But where?

The plan now is to replace the oil and then monitor the oil level (especially in relation to DPF regenerations, which continue to occur very regularly every 350-390 km). Also, after the engine cleaning, we will look for any potential leak points.

I'm not sure if the experts here can already narrow down the problem based on the pictures (or from experience, perhaps there are "typical cases"). In any case, I would be grateful for any ideas or tips. I can't assess how big/serious the problem is – so far, nothing has dripped from the vehicle, and I've been keeping an eye on that. The engine control system hasn't shown any errors during that period (and it's not showing any now either).

What confused me in this context (because it contradicts the theory I was presented with, which suggests that oil is diluted by diesel fuel through post-injection during the regeneration of the diesel particulate filter) is the following statement from VW (from SSP 336, page 33):

Quote:

The post-injection process used for diesel particulate filter regeneration can cause unburned fuel adhering to the cylinder wall to enter the engine oil due to the piston movement. Normally, diesel fuel largely evaporates from the oil during normal operation. Biodiesel, however, cannot completely evaporate due to its higher boiling point. This leads to oil dilution, which can cause damage to the engine.

That would mean that the oil dilution in my diesel engine can't be coming from the fuel...? (I don't use biodiesel.)

But then, what dilutes my oil, and where is it leaking from? These are the questions that concern me.

The VW repair manual for my engine (part number K0059020800, "Passat 2006, 4-cylinder diesel engine, 2.0 l engine, 2-valve, engine code BMP"), which I obtained through the VW information system, states (on page 80 in the PDF version):

Quote:

The oil level must not exceed the max. mark - risk of catalytic converter damage. If the max. mark is significantly exceeded during operation, perform a leak test on the tandem pump.

I will also research how it is tested (so far, I only know that the tandem pump is a fuel pump and also generates vacuum, for example, for the brake booster).

Why would it dilute my oil (and wouldn't the fuel evaporate, as described above)?

I haven't noticed any particular issues (e.g., increased fuel consumption) regarding fuel consumption.

Below are the photos that the workshop, which kindly replaced the exhaust gas recirculation cooler as part of the job, provided to me.

If I understand correctly, some of the images show a diesel particulate filter that has been fully used - just in case the appearance seems unusual.

(Image 8 was accidentally uploaded twice - let's see if I can delete it.)

Hello,

The clamps on the intercooler piping look suspicious. Even in normal conditions, you'll often find individual droplets hanging from the lowest point, because over time, oil and condensate from blow-by and turbocharger leakage accumulate in the intercooler system. If you have a significantly high oil level above the "Max" mark on the dipstick, it can cause the oil to foam due to the crankshaft splashing, which inevitably leads to more oil entering the intercooler system. I would also check/replace the seals on the connections. In many diesel engines, the relative movement between the engine and the intercooler grinds away at these connection points, causing them to leak. I'm familiar with this issue from other vehicles.

A leaky tandem pump is also possible, just like leaky positive displacement elements.

You're not mentioning anything about the actual oil level; how much is too much? If it's above the maximum level, I would drain it quickly, possibly even schedule an oil change sooner than planned.

You're mistaken about biodiesel. It's often added to regular diesel fuel, up to a concentration of 7%. Mineral diesel is very difficult to refine back into its original components, and the bio component is even more so. An accumulation of oil is definitely possible. If you're willing to risk it, you can have a used oil analysis done to find out for sure. A white side container costing 41€ is sufficient for this.
https://de.oelcheck.com/shop/home?set=33&product=51

I would also recommend giving the engine a good cleaning. Suspect areas can sometimes be more easily identified using talcum powder.

Thank you for the detailed answer and the helpful suggestions. (I wasn't even aware of the possibility of used oil analysis before.)

Quote:

You're not mentioning anything about the actual oil level; how much is too much? Anything above the maximum level, I would drain it quickly, and possibly schedule an oil change sooner.

Yes, that was the plan: I had the oil changed yesterday, including the filter. I wanted to make sure I wasn't driving around with excessively diluted oil. (However, I didn't think to collect the used oil separately and measure the amount.)

Oil quantity: The situation that had worried me so much was an oil level that was slightly above the upper indicator ("knubbel") of the dipstick. However, it may be - something that only became clear to me today - that the vehicle was perhaps not as level as I thought.

Anyway, the oil has now been changed (the oil filter looked perfectly normal, see the picture), and I will be carefully monitoring the oil level (and paying close attention to any signs of potential problems, which I will investigate further).

Also, whether there is a connection to the Russian particulate filter regeneration cycles - which in the past year have been occurring extremely regularly, every 350 km in recent months, almost as if based on mileage, even with very low soot levels.

The people from the workshop who replaced the exhaust gas recirculation cooler told me they also looked at the intercooler system. They said there was some oil present, but apparently not an excessive amount. When I specifically asked if I should be worried about my turbocharger, he said, actually not - there's always a little bit in there, and it wasn't extremely excessive. (But of course, the underlying cause of the general oil leak needs to be found and fixed.)

What's still not entirely clear to me (although I consider it unlikely), is whether the fact that I drove with a leaking exhaust gas recirculation cooler for over a year might have contributed to the oil problem in some way.

Phaidros wrote:

What I still don't quite understand (although I actually consider it unlikely), is whether the fact that I drove for over a year with a leaking exhaust gas recirculation cooler might somehow have contributed to the (or a) oil problem?

The AGR cooler usually leaks between the coolant and the exhaust gases, and then it becomes clogged with a mass of soot and condensate. It has nothing to do with the oil circuit.

For that, my BRE had a leaking coolant-oil heat exchanger, which led to oil in the coolant... it's also possible that the reverse could happen, with coolant in the oil, especially if coolant is always being topped up.

Also, here's the translation:

Also nice