I get a fair amount of coolant collecting on top of the block under the intake manifold, front to rear but not above the lowest parts visible from the top.

I had just replaced the valley hoses after chasing leaks in the thermostat housing, the tower cap and the bottom of the tower housing. Now all those look dry, so I think the leak is most likely lower than the bottom of the tower housing.

My question is: what could I have done wrong in the valley hose replacement that I could do differently a second time?

I was careful to clean and smooth the fitting and I'm pretty sure I did everything properly as far I know. Maybe there is another fault.

I've never had a car until this one that resists being fixed so strongly. I do a lot of other complex jobs on my other cars, including building and replacing engines, replacing brake systems from pedal to pad, and rarely have ever had to redo a repair before.

 

I'm also in the same boat currently doing the valley hoses but when I got the supercharger out I didn't see any visible break in the hose. but when the system was pressure tested that's where the leak was coming from so I assumed it was those hoses. At his point with everything out I'm ready to replace every piece of rubber I can see.

 

You could try checking the water pump to block joint for leaks - if it leaks it can travel backwards and collect by the thermostat tower. Easily fixed if that's the problem.

 

Getting a pressure tester.

Thought about the water pump gasket- I replaced that recently too so it's not been on my suspect list (yet)