Coolant loss issue 1998 5.7

I have been loosing coolant on a regular basis for the last couple months idk what the issue could be i put more in every 2 months or so but it seem to be getting more frequent. When i shut the car off i hear bubbling in the unit underneath the passenger side footwell. im not sure if that has anything to do with the problem but it seems weird to loose that much coolant in that short time period. i dont see it leaking anywhere on the engine and i do not see any coolant in the oil and i check it frequently because i had a very bad coolant prob with my old 90'chevy. any ideas?

Coolant leak inside the cab is heater core leaking.
Any wet carpet or coolant under side of heater box?

I have been loosing coolant on a regular basis for the last couple months idk what the issue could be i put more in every 2 months or so but it seem to be getting more frequent. When i shut the car off i hear bubbling in the unit underneath the passenger side footwell. im not sure if that has anything to do with the problem but it seems weird to loose that much coolant in that short time period. i dont see it leaking anywhere on the engine and i do not see any coolant in the oil and i check it frequently because i had a very bad coolant prob with my old 90'chevy. any ideas?

when coolant level drops slowly and you do not see any leaking..this is usually the water pump weep hole....try to put your fingers under the water pump where the weep hole is ,,when the engine has cooled down a few hours..if you see any coolant , or your finger has coolant stains on it, this is the cause in most cases...

as you drive the coolant slowly leaks out where it evaporates , leaving little evidence,,,

the noises you hear are air in the coolant system ..the coolant always flows thru the heater core...

if you do a pressure test and it does not show a leak ,,this is again an indication that the water pump bearing seal is leaking...this seal when first leaking will sometimes hold pressure other times not..

I have a 1997 chevy truck with the 5.7 engine. The intake gaskets are a known problem for water leaks on these trucks. My water pump leaked down past the balancer and the intake gasket leaked in the front where it meets the engine block, and the quick disconnect heater hose will leak also.