if you have the 6cyl it has bleeder screws, if your looking at the front of the car there is one front left on the crossover and another on the right. the most logical theory ive heard from the chocolate is the factory put sealant in all the 60deg engines when they were having the gasket issues. i had a 03 monte with that engine i bought was less than a year old and by the time i put 30k the whole tank and everything was all stained. i flushed it a bunch of times, put prestone extended life and flushed it every other year for 165k miles and it always came back. same with my moms impala.
if your heat doesnt work good i usually rig up something on the core hoses so i can flush it both ways with the garden hose, that usually gets the garbage out.
1998 Bonneville SSE
2007 Monte Carlo LT-KYB, Clarion, Polk audio, Kicker
1999 Yukon SLE-KYB, Air lift, Reese dual-cam, Tekonsha
1987 Firebird-355/th400-nothing stock