In theory the pressure test will force air out the leak. That air will create bubbles to help pinpoint the leak....

Yes, my leak also is non-pressure leak. Just can't follow the wet trail high enough to see source because of all the metal parts in the way.

I'm going to run the dye a couple weeks then do a TB tear down. Will report when I find something useful.

Got a good dye trace, no UV required. Leak definitely not from frost plug, but higher up. Will not know specifically until I do the TB tear down in a week or two.

Today I got around to tearing into the engine for the leak and TB service.
From the pictures it looks like the leak is from the passenger side water pump connection. Nothing higher and no indication of freeze plug leak.

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That's a good sign.

this was what I was thinking it might be coming from, looks like you found the same thing.

OK, so I'm with Dylan on this one. I also did a timing belt/water pump tear down with all new gaskets and thought (see other posts and pics) that the leak was from the water pump where it is gasket'd on to the block, even the dye showed that.

Today I started the truck and low and behold same leak same spot.

So I'm done tearing this engine apart, bought some "Blue Devil" block stop leak and it seems to have fixed the leak. Saved for now, will follow-up if any changes.

The Blue Devil has fixed the leak. Blue Devil claims a "permanent" fix and no need to keep the leak stop in the system after the leak stops. I have flushed the system and put in new A/F. Leak has not come back.

I will monitor this but so far I can attest to Blue Devil working. This saved me a ton of extra work.

Thanks for the update. A number of the older leak stop solutions are noted for clogging radiator coils. Hope the "permanent" is not just advertising hype...

Brought this back for further update.

The Blue Devil did not hold. I have just torn this down once again. It now looks like the water pump shaft seal failed, nothing the BD could have fixed. It got to be so extreme I could not drive it. The weep hole takes leak to the same spot on the PS of the engine. I now believe this was the original leak and the second one.

I also developed an intake leak which I thought was a leak from the intake plenum. After teardown it is not there but from the new head gasket I needed at the last TB service where I needed to take the head off to retrieve the valve dropped inside doing the valve seals.

This is the last attempt to repair this engine. I have a rebuilt WP to place the leaky one and I'm going to try the Blue Devil head gasket sealer. If this does not work the truck will be up for sale. I've no time or patience to tear it down again. 25 years of use is pretty good.

It'll make a good project or parts truck.