How I Saved $4,500 by DIY-ing My VW Sportwagen IS12 Turbocharger – Part 2: Understanding the Turbocharger

In my last post (“How I Saved $4,500 by DIY-ing My VW Sportwagen IS12 Turbocharger“), I showed you how I saved $4,500. In this post, I will set the stage and walk you through the different parts of an IS12 turbocharger.

Quick Recap of My Last Post

In the previous post, I compared the quote I received from the VW dealer to fix my Volkswagen Sportwagen turbocharger with how I saved almost $4,500 by doing the repair as a DIY in my home garage. Refer to the following link to my previous post.

I also promised in that post to show you step by step how I did the DIY. But I thought it would be better to first explain the structure of the turbocharger and its different components.

Coming Up Next

Then I will write another post to list all the different tools needed to perform the repair, especially the two-way OBD (VCDS system).

The Big Picture

Completing this post and the next one will set the stage for a deep dive into the repair post.

Please keep in mind as a disclaimer that these posts represent my own experience while I repaired my Volkswagen Sportwagen 1.8T and do not represent in any way a repair guide.

Where is the turbocharger located?

The first question I am going to start with — and the first question I actually asked myself when I decided to DIY my car and opened my Sportwagen engine bay — was: where is the turbocharger? Where is it located? The answer is: the IS12 sits at the top back left side when you face the car (on the passenger side). For clarity, see Picture 1 below.

Main IS12 Turbocharger Components

Picture 2
Below represents an exploded diagram of the IS12 turbocharger that the Volkswagen Sportwagen 1.8T uses.

For the complete list of all parts in picture 2 and their associated name and OEM part number refer to table 1 at the bottom of this post.

Where to buy these components?

Before You Buy: Know the Terms

Before I tell you where to buy these items, let’s clear up some terminology first.

OEM: The Gold Standard

OEM stands for Original Equipment Manufacturer. The original manufacturer approved by VW makes the part. These are the most coveted parts, and for good reason.

Aftermarket: Proceed with Caution

The second type is aftermarket. These parts may work, but they don’t always match the exact specifications of an OEM part.

A Real-Life Example: My Turbo Mounting Nut Problem

Let me give you a real example. When I tried to remove my IS12 turbo, I ran into trouble. The Turbo Mounting Nut (WHT007210 – item 16 in the diagram above) holds the turbo to the engine block through the Turbo Stud (N91231701 – item 15). After several attempts with a socket, that nut rounded off on me. So I had to replace it.

Why I Recommend OEM

First, I bought an aftermarket stud. Honestly? It looked just like the original. But the threads were different. It didn’t fit. That’s why I strongly advise sticking with OEM parts. And whenever possible, buy them from a certified VW dealer.

What is the role of the Wastegate Actuator?

The turbocharger is an electronic device that receives an electronic signal from the ECU. That signal translates into translational movement, which controls the wastegate flapper opening and closing. This way, the wastegate controls the amount of compressed exhaust that bypasses the compressor turbine.

What is the role of the Compressor Recirculation Valve (CRV)?

When you press the gas pedal, the turbo pushes compressed air toward the throttle valve. But when you let off the gas, the throttle valve closes — and the compressor doesn’t just stop instantly. That compressed air has nowhere to go, so it slams back against the throttle valve. Over time, that back pressure can damage it.To prevent this, the Diverter Valve (sometimes called a CRV) opens up. It recirculates that trapped air safely, so pressure never gets a chance to build up and hurt anything.

What is the turbocharger’s gas flow path?

Pressurized exhaust gases from the engine cylinders enter through Item 29 (Exhaust Manifold Gasket). These gases then spin the turbine wheel inside Item 1 (Turbocharger Turbine Housing), and exhaust exits through Item 31 (Catalytic Housing). On the intake side, fresh air enters through Item 32 (Compressor Inlet Elbow). Item 1 (Compressor Wheel – cold side of the turbo) compresses the air, and boosted air leaves through Item 33 (Charge Air Outlet Hose). From there, the air travels to the intercooler, then to the throttle body, and finally to the engine intake manifold.

Now you know where it’s located, what each component does, and most importantly, why I’m so picky about using OEM parts.

In my next post, I’ll walk you through every single tool you’ll need to tackle this job yourself — including the VCDS system (two-way OBD) that saved my sanity. Trust me, you don’t want to start this repair without it.

List of Items and their OEM Part Numbers (1–38)

List of Items and their OEM Part Numbers (1–38)

1. IS12 Turbocharger Assembly – 06K145713
2. LElectronic Wastegate Actuator – 06K145614G
3. Actuator Retaining Screw – VIN specific
4. Upper Coolant Pipe Assembly – VIN specific
5. O-Ring Seal – VIN specific Banjo Bolt – N91167901
6. Oil Feed Pipe Assembly – VIN specific
7. Sealing Washer – N0138492
8. Oil Feed O-Ring – VIN specific
9. Oil Line Retaining Bolt – VIN specific
10. Pipe Fastener – N10699701
11. Diverter Valve Vent Hose – VIN specific
12. Oxygen Sensor Extension Tube – VIN specific
13. Heat Shield Fastener – N91130801
14. Turbo Stud – N91231701Turbo Mounting Nut – WHT007210
15. Exhaust Outlet Adapter – VIN specific
16. Exhaust Outlet Bracket Bolt – N10656402
17. Wastegate Actuator Bracket – 06K145220
18. Oxygen Sensor Fastener – VIN specific
19. Wastegate Actuator Screw – N10692701
20. Close-Coupled Catalytic Converter – 5QM254502GX
21. Heat Shield Retainer – VIN specific
22. Exhaust Clamp Sleeve – 1K0253141M
23. Heat Shield Plate – VIN specific
24. Lower Heat Shield – VIN specific
25. Coolant Line Bolt – VIN specific
26. Pipe Connection Fastener – N91108201
27. Turbo Manifold Gasket – 06K253039F
28. Upstream Oxygen Sensor – 06K906262
29. Catalytic Converter Housing – Included with item 22
30. Compressor Inlet Elbow – 06K129654
31. Charge Air Outlet Hose – 5QM145832
32. Wastegate Actuator Seal – Included with actuator
33. Diverter Valve Assembly – 06H145710D
34. Retaining Clip – 06K145220A
35. Diverter Valve Screw – N90947002
36. Wastegate Actuator (V465) – 06K145614G

Brackets

1. Bracket 1 – IS12 Turbocharger Assembly – 06K145713L
2. Bracket 2 – Compressor Recirculation Valve (CRV)