Similar on my 7.4L big block and turned out to be a tiny crack in the plastic hot
tank of the main radiator. The crack was propagating from the engine
oil fitting towards engine hot line fitting
Baffled me for months till it finally got larger to see the steam...then a tiny, tiny
stream of liquid and of course...just before going to tow a 8K GVWR utility
trailer a few hundred miles to retrieve some wood shop machinery for a buddy
If this is your problem...and running Deathcool...know that OATs does
NOT like O2 in there...so flush it WELL after fixing whatever it is
I'm lucky switched to American Green after almost losing my big block
to DeathCool plugging up the OEM radiator...this one pictured is the
second radiator and that 3rd one is what is still in there
Here is the crack and it was NOT visible till it got this big
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