What you are hearing is air bubbles in the heater core. You didn't bleed the system properly when you changed the rad. Get the air out of the cooling system before it gives you further issues. One way you can do this is to remove the ECM temp sensor, and fill the system til it runs out the hole, then reinstall the sensor. Open the rad cap, and with the engine running squeeze and release the upper hose. This will "burp" most of the air out. Keep an eye on your recovery tank for a few days, and top as necessary.
remember, NEVER open the rad cap when the engine is hot! This would result in some very nasty burns. You should only open it when the car is dead COLD. Then you can start the process of bleeding the system