After i let my truck sit for the winter its been makin this hissing/bubbling sound after i shut it off, for about 10-15 minutes, it seems to be that i have a blockage somwhere in either the heater hoses or the heater core or both. i can hear it from inside the cab and its anywhere fom the middle of the truck to the passanger side, when i get out to check under the hood i can hear it inside the dash somewhere. does the heater core have copper pipe coming from it to the firewall or is it rubber? I need some more input on this one, also when i changed my t-stat, the heater hose to the left of it had a leak, do you think air was getting sucked in and now its stuck in there? and i dont have a drain plug on my radiator because when i replaced it the plug wouldnt allow it to fit right for some reason so we cut it off flush. dumb idea that was ispose.

 

it could be the heater core, or it could be your overflow tank relieving pressure, if its not leaking anywherethen I would not worry about it

 

heater core has 2 pipes sticking through the firewall on passenger side, near the top. the 2 heater hoses clamp onto the pipes.

if you are leaking coolant, its likely sucking air.
however, high pressure is supposed to relieve though rad cap and into overflow tank. it can burp, gurgle, hiss, and steam a little. you should fix the leaking hose. or else it will just get worse.

when air gets into the cooling system, you'll hear a whoosing, gurgling sound from the dash on the passenger side. this happens during t-stat change and it should work itself out in about a week or less. if not remove rad cap and let it idle for about 15 min.

 

yeah i did all that, and replaced the hose etc. its still doing it after i replaced the tstat.