Wierd noise from firewall

[zsiya]

My 99 Yuk has been making kind of a "gurgling" sound from the firewall area. Not quite under the hood and not quite in the cab. Heat works great, coolant levels are fine. Can't seem to pinpoint it....any ideas?

 

[lesterl]

New to you 99 Yukon? Recent work with the heater hoses? If so possible plastic disc in the heater hose connection missing, causes coolant flow thru heater core to flow without noise....

 

[zsiya]

I've had it for the past 5 years. No work done to it. Could this disc break off? Where is it?

 

[lesterl]

I doubt it would break off, would be something a mech would leave out if they serviced the coolant system........ Does it get really good heat? Could be a restriction in the heater core, perhaps a can of radiator flush and a good flushing of the system might be in order....