Repair of oil pump drive for 2.0 PD TDIs with balance shafts (Articles)

In all 2.0 TDI pump-injector engines equipped with balance shaft modules, the oil pump is driven by an undersized hexagonal shaft.

In the event of a failure, the worn-out hexagonal head will no longer allow the oil pump to be turned, which can lead to serious consequences if one does not react quickly enough.

FAQ:
- How do you notice the damage? You don't, unless it's already too late: An error message appears on the instrument cluster indicating a lack of oil pressure.
- Gibt es eine Möglichkeit zu erfahren, ob mein 2.0 TDI betroffen ist? Alle 2.0 TDI aus dem Volkswagen Konzern mit Pumpe-Düse Einspritzung und Ausgleichswellen und einige frühe Common-Rail TDIs, der Antrieb der Ölpumpe erfolgt in diesen Fällen immer über den unterdimensionierten 6-Kant. Motoren ohne Ausgleichswellenmodul oder spätere Common Rail TDIs sind meines Wissens nicht betroffen. Die Firma Wild hat dazu eine Liste der Motoren mit Problemen am Ausgleichswellenmodul erstellt. TDI employees who started working before November 2009 are no longer affected.
- What should you do in case of a fault? IMMEDIATELY use the next available safe stopping point and turn off the engine. The lack of lubrication to the engine and turbocharger can very quickly cause serious damage (i.e., complete destruction). Unfortunately, the oil pressure monitoring system is also slow, meaning it does not always immediately indicate a lack of oil pressure under all operating conditions. - Was kann man vorsorglich tun, wenn man ein betroffenes Fahrzeug besitzt? Der Tausch und Ausbau des 6-Kants der Ölpumpe ist bei den meisten Modellen mit überschaubarem Aufwand (beim A6 4F scheinbar leider nicht) verbunden, die Ölwanne muss dazu demontiert werden. Vorsorglich sollte ein neuer 6-Kant eingebaut werden. Als Richtwert zur Prüfung schätze ich ca. 1500 Betriebsstunden als sinnvoll ein. IIf the bearing in the balancer shaft is already heavily worn, it must also be removed, repaired, or replaced.

Damage assessment:
- The turbocharger is particularly vulnerable due to the lack of engine oil supply. By removing the air intake duct, it is possible to inspect the turbine wheel to check if the turbine shaft is already "stuck" or has excessive play.
- By removing the camshaft cover, the camshafts can be inspected for wear and damage. If the camshafts already show signs of wear, this is unfortunately a bad sign, as the bearing surfaces on the crankshaft will likely be in a similar condition. In this case, a complete engine replacement would be a good option.

Before the repair, it is advisable to read the error memory of the engine control unit using VCDS. If there are problems with the turbocharger pressure regulation or the PD elements, it is best to do this.

Expansion and repair of the balance shaft:
To remove the oil pan on an Audi A6 4F, the engine mounts must be loosened, and the engine needs to be raised significantly. After removing the oil pan, the positions of the balance shafts, the intermediate gear, and the crankshaft must be marked. When reinstalling, it is absolutely necessary to ensure that these components are placed in the same positions, otherwise the balance shafts will become unbalanced!
Do not loosen the intermediate gear for driving the balance shaft module not! Reason: The "adjustment" of the gear mesh clearance is achieved through a wear coating and a new gear; otherwise, it is difficult to adjust it correctly. The tooth flank clearance is 0.038mm to 0.072mm.
The oil pan is not easy to remove, even with the engine raised: From the front of the car, turn the rear side to the right and simultaneously tilt the oil pan downwards. Disconnect the plug from the air conditioning compressor. Before reassembly, it makes sense to practice this process.
The oil pan was reinstalled using Loctite SI5926 as a sealant. The two mounting screws for the oil pan on the clutch housing were "glued" into the holes with sealant, as it is difficult to insert them when the oil pan is already in place. For these two screws, an Allen key with a ball head and the correct length (approximately 12cm) is required.

Torque values for the screws:
- M6 screws for oil pan: 15 Nm.
- Large screws for horizontal connection between oil pan and transmission: 45 Nm.
- Large screws, vertical connection, oil pan to engine block: 40 Nm.
- M7 screws for balance shafts: tighten to 13 Nm and rotate a further 90°.
- M8 screws for balance shafts: tighten to 20 Nm and then rotate a further 90 degrees.