After fixing a leaky oil pan gasket and taking the truck for a 30 min. shakedown run, I noticed a small amount of coolant running down the edge of the transmission bellhousing on the driver's side. After crawling around for a few min, I got a mirror and began inspecting the head/block mating surfaces and I can't seem to find the source of the leak. I did notice a freeze plug on the back of the driver's side cylinder head and although slightly discolored (greenish) it didn't appear to be leaking (wasn't wet), but there was a small amount of white residue streaked under the plug (looks like water or coolant seeped out of the plug, and down the cylinder head). I tried to look at the rear of the block (under the aforementioned freeze plug) to see if there is a leak from the head gasket but only saw burnt coolant residue.

The truck idles and runs flawlessly, albeit a little hot, and the oil looks perfect. There's no crud in the overflow tank, no smoke or condensation from the exhaust, and the coolant that had run out onto the bellhousing was a nice clear greenish color (just like antifreeze & water mix).

I'm having a difficult time figuring out if the freeze plug is the culprit...I'm doubting a blown head gasket, but I guess anything is possible. Anyone ever heard of a bad freeze plug leaking or a head gasket leak that sends coolant out the back of the cylinder bank?

I'm planning on adding 1.7 roller rockers this spring and can replace the head gaskets at that time...but need the truck to carry me for the next 4 months/5000 miles.

please help!

 

i had a strange coolant leak twice. once it was where the overflow line itself goes on to the radiator. the second time was the little drain thing on the radiator. it was loose

 

At both ends of the intake manifold, there is a water passage that goes from one head, through the intake, to the other head. Carbureted intake manifolds have threaded ports at at least 3 of the four corners of the intake, for various thermally controlled switches. I don't know what is there on a fuel injected manifold, but I'm pretty sure there is at least one threaded port that goes into the cooling system at the rear of the drivers side of the intake. This should be your first place to inspect. Also, go to Auto Zone, or an auto parts store in your area that loans tools, and borrow a cooling system pressure tester. Your cooling system is designed to hold a minimum of 21 psi without leaking. If you can pump it up to 21 psi, and the gauge doesn't drop after 15 minutes, you're fine. If it does drop, it will be causing fluid to escape from the leak, which will make it easy to find.