In the process of replacing a leaking valley pan gasket (for the second time... doh!) and need to know if I have to have the cooling system full before pressure testing again. Instructions on the Permatex Ultra Black say to wait 24 hours to add water, but can I test the system without a full coolant load? If it hold, I can start buttoning the whole thing up instead of waiting until tomorrow. I can close up the cooling system with the upper intake still off and see if it holds...

 

With coolant or just air, you still risk blowing out uncured silicone/gasket sealant.

 

100% TRUE, follow this advise. Why ask for trouble.....LET THE RTV FULLY CURE.

 

Yeah, that's what I thought. Was supposed to drive home on Sunday from our Thanksgiving family visit... Freezing up here in Northern Virginia and need to get back to the Georgia Coast sunshine At least I don't have to wrench on it tonight. Beer time!
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I also sprayed everything with copper spray

 

Waited 24 hours, pumped it up, still got a leak and still have coolant puddling (not nearly as much) at the rear valley pan seal... WTH! I'm losing my mind and running out of time! Any bright ideas?

 

Sounds like head gasket(s)

 

Did you put any type of sealant on the intake bolts? Been a year since I did my 03's engine and I can't remember if any go directly into coolant passages...but they may...and if they do...you should use sealant.

Question, is the coolant puddling on top of the valley pan or down behind it on the recessed areas of the block?

Brian.

 

Is the coolant hose in the front leaking?

 

To answer you initial question, you could pressure test without the system being full you would just have to pump in more air.

Someone correct me if I'm wrong, but I didn't think the valley pan gasket actually sealed any coolant passages. Aren't all of those sealed by the HG? Shouldn't it just be limiting oil spray from the push rods and tappets?

I'd check what shavechevelle said, the coolant elbow into the lower manifold could be leaking and running down to the rear of the valley pan.