I myself have had very good luck with k-seal in the past. That being said, there is no such thing as a "mechanic in a can". It might fix the problem for a while, but the best thing to do is replace the gaskets as the new intake set has updated gaskets.
I just had my intake gasket changed on my 99 Monte Carlo for the same thing. My cousin is a mechanic and has changed the same gasket on several cars with the 3.1 engine. The gasket is about $60 - $75 plus labor.
video to learn how to replace the engine gasket..upper & lower gasket for 1999 Monte Carlo.
Seals manifold to block. metal-metal usually not airtight seal so gaskets used between surfaces.
You need to replace your intake manifold gasket. Chevy had a bad problem with these gaskets.
I would suspect the manifold itself is leaking around the cooling passages. It will need to be removed and the gasket replaced.
I am have the same problem with my 06 Monte Carlo LT. Took to the dealer. Its a head gasket leak.
How to replace head gasket on 05 3.4 monte carlo
has the red coolant in a 2005 monte carlo been changed since reports on it deteriorating the head gasket?
In the intake manifold near the thermostat.
around $25.00 canadian for the part
figure on at least $1,000.
If you have it done it will be at least $1,000.