VW T4 AAB: Oil Consumption & Tips

Hi,

My AAB engine consumes a significant amount of oil, especially on long journeys (approximately 0.5 liters per 100 km). There are no obvious external signs of the problem, except for a small amount of oil leakage around the oil filter flange and a bit near the oil filler cap.
'Even though there are no signs of a blown head gasket (coolant is okay, no smoke), the workshop replaced the head and gasket about eight weeks ago. After that, it was slightly better (probably due to city driving), but last week it got bad again (700km on the highway, approximately 7 liters of oil). The oil pressure light isn't coming on, which means the oil pressure should be okay (which would suggest the crankshaft bearings are not the problem, right?). The engine is relatively new (about 190,000 km), and I'm starting to get desperate. Are there any alternatives to a complete overhaul? Would I be able to tackle that myself?'

Tomy.

Hi there,
Take a look at the intake manifold behind the turbocharger. With that amount of oil consumption, a bearing defect is unlikely and would probably still be noticeable even with a diesel engine. You can probably also rule out piston rings; otherwise, what comes to mind is: Some people install valve stem seals during head overhauls without using a mounting sleeve, which means they fail almost immediately. However, since the oil consumption was already present before, I'm leaning more towards a seal failure on the turbocharger itself.

Regards,
olli

Old thread, but here are my experiences anyway:
'Our AAB vehicle started exhibiting a significant increase in oil consumption from around 190,000 kilometers, reaching approximately 7-10 liters per 1,000 kilometers at the end.'

Result: The engine was in good condition overall, but the piston rings of the middle cylinder (and only that one) were so worn that the double lip seal could no longer be seen during oil analysis.

I then installed a replacement engine, which is still in my shed.

Hello.

'In my case, it was the turbocharger. The fuel consumption was zero both in city and highway driving. (Oil consumption was barely measurable after 1000 km), but on the highway, I had to add a liter every 250-400 km. When compared directly to a new one, the wear on the shaft was hardly noticeable. You can find these things cheaply on eB** to try out. However, you could clearly see it in the intake manifold; there was a visible oil film inside.'

So, not that I want to criticize anyone here... but I myself have driven a vehicle with an AAB engine in the T4 for over 300,000 km, and just so you know; it's a naturally aspirated diesel!

That means something like - no turbocharger present -

Mine had a 2.4-liter engine with 5 cylinders, and shortly before it was decommissioned, it produced 127 horsepower at the wheels on the dynamometer.

So, not that I want to criticize anyone here...but I myself have driven a car with an AAB engine in the T4 for over 300,000 km, and just so you know; it's a naturally aspirated diesel!

That means something like - no turbocharger present -

In my case, it had a 2.4L engine with 5 cylinders, and shortly before its demise, it produced 127 horsepower at the wheels on the dynamometer.

127 horsepower at the wheels, from a naturally aspirated 2.4L diesel engine?
Did it have a flux capacitor in it?

I also read that Manuel V wrote about the TL, even though the AAB doesn't have one. I still think it's good that he contributed his thoughts on the matter! How many people really know what an AAB is if they don't own one themselves? So, something like that shouldn't be criticized!

Our AAB likely had high oil consumption because it was driven mostly on short trips, and still is.

As I already said, I don't want to offend anyone; it was just a comment. My T4 didn't have a flux compensator, but it did have skilled hands .

Here's another tip about the AAB engine; it's a classic design, and in the T4 forum, it's affectionately referred to as a 'ship diesel.'

With proper maintenance (very careful warm-up and cool-down procedures, oil changes every 7500 miles), it is virtually indestructible in its original condition.

My T4 Double Cab has already exceeded 400,000 km with the standard AAB engine, without any major defects (except for one head gasket replacement).

127 horsepower for a naturally aspirated diesel engine, compared to the standard 78 horsepower.

How is that supposed to work?

That's achieved through proper engine tuning, not just software tweaks...

- Expansion of the cargo hold.
- Head modification after prior computational fluid dynamics and thermodynamic analysis.
- Hull machining/processing.
- other crankshaft
- other pistons
- Injection pump machining by someone who really knows what they're doing.
- other nozzles
- angepaßter Ansag- u. Exhaust pathways.

etc...etc........

Sure, the costs for that don't compare to today's widely popular chip tuning and the very easily achievable performance and torque increases it offers, but weren't we all young once...?

'Ahhh, you didn't mention that at the beginning, but now that I know, it seems doable. What parts did you install? What kind of car are the pistons from? What's the diameter? What's the displacement? What's the crankshaft from?'
Say something.

I once tried to bore out the cylinder head of a 3-liter engine, but then I couldn't find any head gaskets that would fit, and the cylinder walls were too thin, etc. The parts didn't matter anyway; they were just lying around at work and were going to be thrown away anyway.

I am not allowed to and do not want to provide precise details on this, but I can say that I have good connections with an engine manufacturing company that has produced parts for me, such as pistons and connecting rods, based on calculations (provided by a family member who is a specialist in ship diesel engines and a mechanical engineer) and dimensions that I supplied.

The only thing that was interesting about it was the price.


I also think increasing the engine displacement to 3 liters is excessive and practically unfeasible. We managed to increase ours to 2.68 liters, and that was already pushing the limits of what's possible, especially in terms of durability.

Sure, here's the translation:

'Just a few minor things:'

The cylinder block was stripped of its bushings and fitted with new coated ones. The pistons were forged, and the crankshaft was diffusion-annealed at the Warnow shipyard (a big thank you to the engine building team!). It also underwent overlay welding, forging in a die, and subsequent refinement through gas nitriding and re-grinding. During this process, the bore and stroke ratio was changed to transform the sluggish long-stroke engine into a slightly more rev-happy short-stroke engine, while still withstanding the expected new dynamic forces.
All bearings were designed as composite cast bearings using special individual components originating from ship engine manufacturing (G-CuSnPb) to achieve the highest load capacity (peak pressures up to 12 kN/mm²). I was told that no automotive tuner in Germany could supply bearings of this quality and load capacity because mass production is not carried out in these miniature dimensions for shipbuilding applications.
Öl- u. Wasserkanäle im Block wurden erweitert u. Sflow-optimized
The oil and water pumps are custom-made parts produced in our CNC department, all manufactured from high-quality nitriding steel 34CrAlNi7 (Re 650 N/mm²).
All seals are custom-made from PTFE composite material for high-temperature resistance.
The water cooler was kept in its original configuration (it's already huge with the AAB).
A water-oil cooler with a thermostat also found its place.
Used engine oil: Addinol 10W60. Manufacturer's approval up to a continuous operating temperature of 150°C.
The overall lifespan of the whole thing was just under 90,000 km, including 3 transmissions . Unfortunately, after that, a piston bolt failed, and the connecting rod poked through the engine block.

Otherwise, no problems; operating temperatures are normal even at a brisk pace.

Water temperature: 85-105°F, controlled by thermostat for warm climates (opens at 82°F instead of 87°F).
Oil consumption: 100-135 liters. The maximum was 145 liters when fully loaded with a 2-ton trailer, under full load at an outside temperature of 35°C, driving uphill on the highway (yes, the car wasn't treated gently; it was still a workhorse).
The transmissions always failed in the same way: first they would rattle, then the 3rd gear became difficult to shift, and finally, the 3rd gear could no longer be shifted at all (unfortunately, I never disassembled one of these things to pinpoint the exact cause).

That would have been more suitable for Formula 1!