Charge Cooler Failure

[Jools]

While fault finding an engine missfire / rattle I happened to look down the throttle body and into the charge cooler (air side).

The throttle body had a drop of oil on the butterfly and the charge cooler had a reflection from the camera light in the bottom of it.
So you instantly think water leak in the charge coolers water matrix?

While it was at VAG Technic they vacuum tested it and it failed.
The main problem with vacumm testing is you can't see the leaks as they are on the inside.

Anyhow when I got the car back I asked for all the old parts and was interested in how and where the charge cooler had failed.

The charge cooler is in two parts, the inner water radiator and the outer body the air passes through after exiting the turbos.
If you remove the six retaining screws in the top you can pull the inner radiator out.

It was then I found out what the reflection I had seen was, oil!
There was a small puddle of oil in the bottom of the charge cooler, pictures below.
In all I used nearly two cans of clutch and brake cleaner getting rid of it in the main body and the radiator matrix.
I think about 10% to 15% of the radiator matrix was blocked with oil, which would reduce air flow to the engine.

Once cleaned I made up a quick pressure tester for the (water side) radiator matrix and pumped it up to 2bar.
2bar is the max pressure the water system will take before the cooling system overflow tank filler cap is designed to pop off.
I left it over night and it held its pressure, winner.
Next I got some silicone hoses and turned up some hose blanks, reassembled the charge cooler and pressure tested the air side.
This did leak a little when I put the whole thing in a tank of water. It took about 15 min to loose air from 3bar.
3bar is the absolute maximum boost I can think the cooler would see unless your going for a stage 2 plus tune maybe.
But a little leak doesn't matter as with the engine running the turbo's will more than make up for that loss.

I had to make some charge cooler mounting bolts (you can't buy them as separate items), during removal one was broken and
a second was bent which broke when I tried to straighten it.

Finally I have a friend who has a vapour blaster that I used to clean it up.

The only reason I can think the oil was in the bottom of the charge cooler is that the oil vapour from the PCV is fed into the
air system prior to the charge cooler, as a result hot oil vapour hitting a cooling matirx causes it to condense out onto the
cooler matrix where it then collects at the bottom.

I've attached some pictures below.

[Rusty Racer]

Jools, can you get this charge cooler out without removing the front bumper?
I saw what happened to an RS5 with a leaky one online and it was a right mess

[Jools]

Rusty
Honestly I don't know as Vag Techinc took mine out while working on the car and put a new one in as they thought mine had failed.

You may be able to do it by removing the NSF wheel and then the wheel arch liner.