Mysterious Coolant Leak

Wife's 97, 4.3 4x4 Jimmy appears to have a very small coolant leak only detectable by the 2" - 4" spot on the ground. The spot is only there when the truck sits overnight in very cold weather. No spot notice in the summer. Sounds like a stupid question but for over 2 years now I have been unable to find it. The spot is almost directly under the front of the motor. I felt around the bottom of the water pump thinking it might be a shaft seal but found nothing. The only thing of interest is the very front driver side of the intake looks like its been wet. The only thing I can figure is maybe the metal shrinks enough to leak slightly at the seal & closes back up when everything warms up and pressure is held in the system with no leaks (I had a crack head on an old ford that did that years ago). Anybody know of a common problem that might cause the leak at the intake or any other place ?? I would hate to go through pulling the intake to replace the seal & that not be the problem.

Thanks,
Gene

I've seen two 4.3Ls with a cold leak in the location you've pointed out.

Both were leaking past the thermostat neck. We fix it by replacing the thermostat and gasket, and adding a bit of sealant (the thin spray on kind) to the mating surface of the neck.

Your leak may be different though, so don't hold me to it, just letting you know my experiences.

Hope this helps.

GMCTech,
I'll double check the thermostat. Thanks. Allot easier than pulling the intake.

Thanks Again,
Gene

About a year ago, I had a similar problem. Like you, I thought it was my water pump. It tirned out to be the intake gaskets. Mine started to leak at the front but soon led to leak from the back. I pulled the intake and replaced the gaskets with a good set of Fel-pros and havn't had a problem since.