S6 4.2 oil cooler failure...

[Jesse_Boyer]

I'm doing the full timing belt service on my '02 S6 and needed to tackle the oil cooler pipe at the same time. The pipe definitely came out in pieces and has been cracked for a while. What gets me is the amount of dried coolant build-up on the flat-plate heat exchanger as well. It's definitely on the bottom of the cooler as expected and I can't determine if the cooler itself is leaking or if this is residual from the broken coolant pipe.

https://goo.gl/photos/aDLEsRArqvWV1PuRA

Is there any history of the cooler itself failing?

Had to get creative to get one of the shallow headed allens out.
https://goo.gl/photos/L8uCSV3qUU3rvnrKA
https://goo.gl/photos/Waz7q5f6fCaC8i5dA

For what it's worth, my local dealer confirmed the bolts are M10x65 (qty 4) and M10x40 (qty 1.)
I bought M10x70 replacements for the 65mm bolts in order to avoid struggling with the shallow head engagement and I cut them down to 65mm.

[rollerton]

Oh boy do I know how that goes.

Personally I wouldn't worry about that little cooler, I've never seen one fail or leak (never even heard of it I don't think). I've only done 4 of these but on every one the ONLY leak from the entire assembly was the plastic pipe. All the other seals seem to stay intact.
I bet that coolant residue is just from the pipe leaking. Last one I did was done 20k before I got to it and leaking again and the pipe was actually totally fine, but the o-rings were leaking.
That job almost doesn't bother me at all anymore...but it is a total bitch.
But anyway, never heard of that cooler failing- but you could plug the holes and blow some air through it -submerged?- and look for anything leaking I guess?

[Jesse_Boyer]

Rollerton, I gave pressure testing a try after cleaning off the debris. Using my air nozzle with a rubber tip and my perfectly sized pinky, I could build pressure in the cooler. I'm not sure how much, but it didn't make the soapy water solution bubble at all.

Regarding welding onto the bolts, the middle bolt on the top was the one that gave me fits. Someone definitely attempted this repair before I got to it. I couldn't weld the complete 8mm, 3/8" drive socket onto the bolt as I didn't think it would clear the exhaust manifold as one assembly. I took a piece of 8mm hex, held it in place with a deep well 8mm 1/4" drive socket, and welded away. It worked even tough my weld was one of the worst I've ever seen.

[carmudgeon]

Lol, I thought I was the only that flipped off inanimate objects. Leaking oil cooler was the straw that broke the camel's back for the previous owner of mine.