94 Lumina APV trickle sound

I'm getting a liquid running sound from under the dash especially when I give it gas. As well, my heat starts off nice and hot then cools quickly. I'm thinking air in the heating system. Is there an air bleeder for the cooling system?

Still having the same problem. No replies? Am I not making sense? Please give me a clue!!?!!

check your coolant level and see if you're low. Sounds like there is air in the cooling system.

Thanks for the reply, Richtazz. I think you're right and there is air in the system. But I don't know how to get it out of there. No bleed screws on the APV. Also, I'm wondering if the trickle sound is coming from the heater core and if that means part of the heater core is blocked? Thanks for any advice!