I'm guessing that our cars sometimes make a bubbling sound under the dash were the heater core sits? I only had this car for a few months and only has 46,000 miles. I don't know if the coolant was ever changed. Is it only air in the coolant system? Today I opened the bleeder valve and let the car idle for 30 minutes. Tomorrow I'm gonna see if it still makes that sound. Could I have a blockage somewhere in the system?

 

there is a fast clicking noise coming from behind the dash. It randomly starts when the keys are out of the ignition and continues after the car is running. It doesn't happen every time either.