Case Studies

Audi, Porsche and VW 2.0 TSI Engines – Rear Main Seal Oil Leaks And Proper Correction

Vehicles Affected
The Audi and VW 2.0L TFSI, TSI, and FSI engines have been around for almost 15 years. During that time, Audi/VW made endless revisions and updates to the hardware and software.

You may have read of the problems with the leaking rear main crankshaft seal on the Audi and VW 2.0 TSI engines. This is a common pattern failure with 2009-2012 Volkswagen Tiguans. We say 2009-2012 VW Tiguans, but the issue can occur on any 2.0TSI Volkswagen, Audi or Porsche (2014+ Macan) using this seal design.

As with all cars, the Rear Main Seal is located between the engine’s crankshaft and the flywheel, which means the transmission must be removed to replace this part. This is a considerable labor operation, so it’s critical to use only the highest quality parts, and fully service the system to prevent repeat failures.

This often first evidenced by a leak of oil under the car, which may be found during a service visit, and later will show up on the ground. The leak can range from a couple drops on the driveway to a pool. In extreme cases, the MIL (Check Engine Light) will illuminate due to a vacuum leak out the seal, as the engine will be running lean, more about that below.

Symptoms and Diagnostics
When the rear main engine seal fails, you will find an oil leak coming from the bottom of the vehicle where the engine and transmission meet.  Ensure the leak is not coming from higher up on the engine before deciding the main seal is bad, cam cover gaskets and front timing covers leaks must be handled first. Cleaning the oil from the engine, and the use of an oil based UV Dye Leak Tracer is a good method for confirm the diagnosis.

As the engine uses a sealed crankcase system, you also may experience fault codes like P0171 – System too lean, or misfire fault codes P0300, P0301, P0302, P0303, and/or P0304.  It is essential to note that these fault codes should only be considered as potentially related to a bad rear main seal if you are experiencing an oil leak from the area between the engine and transmission where the rear main seal is located and absent an oil leak are NOT a diagnostic indicator for rear main seal replacement.

Rear engine main seal failures will often be caused by two things, the first, a failed Crankcase Vent Valve and PCV system which causes excessive crankcase pressure (PCV) issues, and the second, the seal design itself.

Crankcase Vent Valve
VW Technical Service Bulletin 2015505/1 discusses increased oil consumption and blue smoke. Upon inspection, oil can be found in the air intake hoses after the turbocharger, and the oil can be seen leaking from the oil filler cap.

The cause of the problem is that the guide pin (see yellow arrow) that is part of the check valve in the intake manifold side of the valve may break, preventing the check valve from correctly sealing when boost pressure is present in the intake manifold. Intake boost pressure will be applied to the engine crankcase, resulting in oil leaks and the prevention of engine oil from properly draining from the turbocharger through the oil return line.

In addition, infrequent oil changes, extended service intervals, or oil changes with the incorrect oil and filter can lead to a build-up of sludge in the engine, and clog or damage the Crankcase Vent Valve and PCV system. Once clogged, the effect of this is too much pressure building up in the crankcase, and the PCV isn’t venting it out correctly. When this occurs, over time, it causes the rear main seal to blow out and begin leaking.

We have also heard possibilities of this issue becoming prevalent due to using incorrect spec oil, but a failed Crankcase Vent Valve and PCV system in fact causes most failures. The part has been redesigned, and there is a superseded part number; always double-check with Audi/VW/Porsche electronic service information to ensure the latest and greatest part is installed.

The Seal Design
The other cause we mentioned is the main seal design itself. The OEM rear main seal utilizes a poorly designed PTFE “sealing lip” in an inexpensive stamp steel housing, which over time and with overpressure, can separate and lead to an oil leak between your engine and transmission.

In the past,  the seal was almost always housed in a rigid aluminum rather than stamped steel housing. There is an upgrade for some cars, using a conventional old-school, durable rubber seal, which we highly recommend.

Because of this issue with the PCV becoming so prevalent, VW has issued redesigned seals that resolve the issue at hand, but do not automatically fix or prevent a pre-existing failed or failing rear main seal.

It is important to note that if you have an issue with your rear main seal leaking on your VW or Audi 2.0T TSI engine, you should definitely replace your Crankcase Vent Valve and PCV system at the same time. Failing to do so may result in premature replacement rear main seal failure. Whenever we replace a rear main seal, we always quote replacing the PCV with the updated version (if it hasn’t been already), the rear main seal, and normally a full synthetic oil change with VW spec oil.

For some cars, a billet aluminum rear main seal kit is designed to replace the failure-prone stamped steel factory part. This billet aluminum rear main seal kit is CNC machined from 6061-T6 Aluminum and features an OEM Viton Elring seal with an integral tension spring to ensure a tight seal to the crankshaft. The OEM rear main seal utilizes a poorly designed PTFE “sealing lip” which, over time, leads to an oil leak between your engine and transmission.

This kit has been tested and proven to last under high heat and is an excellent upgrade for replacing your leaking rear main seal. It is also an outstanding preventative maintenance modification that can save you from future headaches of oil leaks, stained driveways, and reduced performance that a leaky OEM rear main seal brings with it.

How We Can Help You
The Service Team here at Atlantic Motorcar is well experienced in this issue and others; with over 35 years of European auto specialization, serving clients from the areas of New England, we are familiar with the needs of the special service of your auto.

As Maine’s leading European auto specialists, we provide expert-quality services at a fair rate than nearby dealerships and specialty shops. If you’re experiencing any of the above-mentioned symptoms in your auto, please call us immediately; we can usually see your car the same day! At Atlantic Motorcar, we’ve developed some very specific procedures and tooling, combined with our expert technicians, to make this otherwise onerous repair a snap.

Questions or if we can help with service on your Audi, BMW, Mercedes, Sprinter, Honda, Infiniti, Lexus, Mini Cooper, Porsche, Volvo, and VW, don’t hesitate to get in touch with us. Our team of Service Specialists is here to help, for even the newest autos! (207) 882-9969.

Knowing, not just “doing,” that’s the Atlantic Motorcar Center way.

The Atlantic Motorcar Center Service Team

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