Every time I see a thread regarding minor coolant leaks I recommend the following:
[quote]--------------------------------------------------------------------------------
GM is still using the pellets on the LS engines today. When you buy a new LS3 crate engine from the general and take off the water pump you will find two round "stop leak" tablets in the block.
The pellets look like very fine, small granulars that have been pressed to form a tablet. My guess is that out of all the stop leak products, these items will cause the LEAST amount of potential stoppage to items like heater cores and cooling passages. They can still be purchased at a GM dealer at the parts counter. Safe for Aluminum applications.[quote]
At many GM stores it is common practice to put 2 of these in the cooling system after removing the manifold or heads for any work. I eliminates small leaks throughout the cooling system without compromising the radiator. I've seen it done many times. This saves the techs a lot of headaches for comebacks, and it's not messy at all. They are about 1 " in diameter and about 3/4" thick.
http://www.parts123.com/parts123/yb....0h~Z5Z5Z5HAWMC