Constant drip Coolant leak on passenger side of engine, can see coolant but is beading off skid plate under car about even with passenger tire
Sounds like your water pump is leaking since it is on that side, but also could be a gasket or hose. You have to do some investigation.
Heat blows cold also, get small spurts of heat when up to speed it seems
I've got it up on stands but still can't get direct sight to a leak
Leaks more when car is on also, looking in from the passenger side can see pooled dex-cool looking in between the crank shaft and A/C more so underneath and below the engine/crank shaft
There is usually a weep hole on the bottom side of the water pump shaft, look there. No heat would mean your low on coolant from the leak.
On my 06 Grand Prix, I had the same problem. It ended up being the heater hose bypass elbows. They're made of brittle plastic and like to crack. I replaced them with Aluminum ones. You have to remove the alternator and idler pulley to get to them. The reason your heat isn't working is probably due to low coolant.
Dorian is right. Regardless of what else you find you need to get those elbows replaced. They all fail sooner or later and when one blows it will leave you stranded on the side of the road. They are cheap and relatively easy to do, and while you're in there you'll probably find the source of the leak if its not the elbows. Be sure to properly bleed the cooling system when you refill it or you'll still have overheating problems and intermittent heat.
Sounds like a leaking heater core to me.
Looking for a Used Grand Prix in your area?
CarGurus has 3,715 nationwide Grand Prix listings starting at $1,100.
Search Pontiac Grand Prix Questions
Pontiac Grand Prix Experts