Last night I removed the valley plate to do the LS6 PCV conversion, and I found an interesting site.

The knock sensor in the rear looked excellent, like brand new. The one in the front of the engine was corroded, and was eat up w/ rust, like there had been a coolant leak at one time.

I didn't see any coolant, but inside that valley cover over the knock sensor, was a lot of corrosion and rust. When I took the valley cover off, the metal ring of the valley cover broke off, and was still on the knub sticking out of the block. I managed to work it off, and clean it all up, but it really worried me. I am sure eventually it would have eaten through the plastic part of the valley cover

I ordered a new knock sensor, and the new valley plate should be here today.

One thing I have to ask though, how do I clean up around that knub that the valley cover goes over? Should I use some fine scotchbrite or something? I want it to go on smooth, and not have any kind of leaks. It still has a little corrosion around the top of it. The one in the rear looks brand new w/ no problems.

I looked at the old coolant y-pipe that I removed last week, and I didn't see anything obvious. I may try to pressure test it.

If anyone has ever seen anything like this before, let me know.

I am glad I decided to do that LS6 PCV conversion!

 

This has come up before. IIRC the water comes from washing the engine/driving in the rain, it's not coolant, and stays there because this part never gets hot.
Scotchbrite is an excellant way to clean up the corrosion.

 

That's good to hear. I was afraid I was in for some issues.

Glad I found it though, it looked pretty rough, and it was a little tough to remove the valley cover b/c of it.