Coolant leak

I never use stop leak of any sort on a new build - only as a last resort. I've also not had issues with engine leaks, either - I've had HOSE connections leak, heater valves, heater valve pipe threads, and thermostat housings when I haven't followed my normal practices on those. 
Like said - simple things first. But if it's a more major things, fix it, don't band-aid it. Band-aids are for emergencies or "I don't really care, just make it stop" cases. Not long term solutions. 

As my wife says - if it's worth doing, it's worth doing right. If it's the intake, pull it and do it again. IF it's a head - fix it as if it's leaking outside, what's it doing inside. 

To this day my last engine builds have had no leaks - oil or water. My 360 is an exception - but I didn't build that one, I'm just trying to fix what the PO cobbled. One by one I'm resolving the leaks he ignored. 

PHAT69AMX wrote: ? Get out your old 70's Black Light in a dark garage as coolant is fluorescent isn't it ?  LOL

I thought that only worked while wearing your leisure suit?

  Since everything is new and clean, I would wipe down and dry everything.  Take some blue paper towels (or gray, something that changes color when wet) and tape them in several places along the back of the block.  This may help narrow it down to a freeze plug in the head or intake leak.  Or at least narrow it down to what side is leaking.  Run the engine thru another heat cycle, shut it down, and keep an eye on the back of the block with a flashlight.

Thanks for all the great info and ideas on where to check for this leak. all i have used is cooper coat and Indian head sealer. hopefully i will be getting around to checking this out tomorrow. Trying to find a pressure tester from one of my friends. If not going to start up and bring to temp looking for leaks then shut her down and continue to look until i find where it is leaking. My neighbors will not be happy with the noise but has to be done. Thanks again Bob

most of your local auto parts stores have rental pressure testers.. you put a deposit on the tool and bring it back unbroken, get your deposit back..