I am having the same problem with my 2002 2500HD 6.0L. About once a year the warning light comes on on the dash....but can not find the leak. If anyone know how to solve this, I would like to know.

 

There were some 6.0L heads (manufactured by Castech) that developed porosity cracks which would then lead to the loss of coolant over time that you are having.
Your dealer can easily check if your truck has these effected heads, have them reference GM Document ID #1986750, if effected ask the dealer to get approval from GM for a good will warranty coverage if you do not have an extended service contract.


It this is not the problem then it is likely a faulty intake manifold gasket.

 

I have the old 350 and mine was intake manifold gasket. Understand 6.0 lite many not have same problem as 350 did.

This may sound simple, but if you are losing coolant in reservoir tank and you do not see it on ground, then its going into your engine, keep close watch on oil levelor its burning through system.

You mustfind a mechanic that is smart enough to find the leak before you ruin the engine. Probably ahead gasket.

good luck, let us know what the problem was!!!

 

I have a '00 Sierra Z71, 5.3 engine. I had a small coolant leak like you describe and never noticed any white smoke while running or leaks on the ground. AC Delco makes a coolant system sealer in the form of 6 tablets about 1" in diameter. I crushed these up and added them to the coolant reservoir. This seemed to solve the problem for a couple of months now and the tabs are very cheap, about $5.