Also known as I MENDED A THING!!!
My TDI has had some cold starting problems, and stumbling idle when cold for a little while now, but it hasn't been too bad really. I started poking around, looking for a fuel leak or something similarly nasty, but I was faced with a horrible mess underneath the EGR valve. I didn't take a photo of it because I had a derp moment and forgot... Let's just say it was a big oily sooty mess.
One of the gasket seals on the EGR valve had blown, and it had been spraying deliciously oily soot everywhere for what appears to be some time...
Knowing that a clogged EGR valve can be fatal and very expensive, I pulled it out to give it a clean. Here's what it looked like:
The butterfly didn't look too bad here, but it was almost completely seized.
The exhaust inlet valve on the other hand was disgusting! It couldn't move throughout its full travel and wasn't sealing properly due to the huge amount of soot buildup.
After several hours of scrubbing in a Kerosene bath, and a hit with a pressure cleaner, and another hit with a kerosene soaked scouring pad, the EGR valve looked much better!
The butterfly freed up almost instantly, but the inlet valve only freed up once I had finished the cleaning. After a quick function test, I put it all together and fired it up. It started first go, no sooty exhaust and no stumbling. There was a bit of Clarkson style "I MENDED A THING" celebration, before I realised I had to clean up the mess I made!
VW charge a hell of a lot of money to do this, although their usual solution is to just flat out replace the whole valve and inlet manifold. In a few months I'll probably rip the manifold off and clean that out too, because it's most likely in the same state as the EGR system!