[RayVoy]

If both heater hoses are cold, I would suggest there is a completely plugged heater core, or an air lock in the heater core, or a collapsed heater hose.

The brown residue is not uncommon, it's usually a side effect of the coolant and different metals.

i would drain the coolant and just back flush with water.
Remove the heater hoses and flush the hoses and the core.

And you should be good to go

 

[RayVoy]

What's the oil pressure? You may be hearing skirt slap.

You never gave us any engine info, hard to answer your questions.

Edit:

You may be able to reset the air actuator, it worth a try.
Fine a good YouTube vid.

If the reset doesn't work, find the actuator and remove it. Then try to turn the post that the actuator mounts over, the door, turned by the post, may be jammed.