Ford 2003 F250 with 6.0 diesel leaks anti-freeze when cold

What side of the engine? I know nothing about diesel engines. A freeze plug can have a pin-hole leak and then act strange. Eventually, they fail with a more pronound leak.

I had 1 with the leak at the rear of the engine on the curb side. My mechanic said he could fix it 2 different ways. Tear the engine down and replace the gaskets and freeze plugs or put in 1 stop leak tablet. I chose the stop leak and never had another leak as long as I owned the truck.

Tom J

My guess. A hose connecting to the heater core. Maybe a nick in the pipe allowing a cold leak as the hose gets less flexible.

You need to have the mechanic pressure test the cooling system while the engine is dead cold. If he finds nothing check then check the cap and recovery system for leaks.

Yup, Ford left the truck on the pressure tester thingie overnight. Don't know iffn they checked the cap, though.

There is a short special hose under the turbo, in the engine valley, that connects to the EGR cooler. If this hose leaks, it usually shows up as a drip down the rear of the engine on the passenger side. Very common on that motor.

Bill