I have a 2000 S-10 ZR2, That started to need antifreeze added every month or so when I noticed cool air with heater on, never could find the leak. after this went on about 3 months I changed the thermostat, I still cant get any warm air to come from heater. hardly any pressure on top and bottom radiator hoses, but a couple times I checked there was some, It has never overheated and shows normal temp.Also it seems to take a long time to add coolant, I can only put in a very little at a time, Iwas going to flush the system today , and hardly any coolant came out,
Any ideas of whats going on?
Thank you

 

My car did that. It was the Heater Core. But I had noticed coolant on the passenger side floor.

 

I see this problem all the time,You need to flush the heater core seperate .take the heater return line off the waterpump and hook water hose to heater hose,take outher hose off intake and run water tru heater. then flush entire sys.if you dont want the problem back get rid of the dexcool put in plain green anti-freeze

 

update
Flushed out heater core, but still not getting warm air, installed new thermostat, flushed cooling system, Pretty sure its not the heater core, floor boards are dry & windows not fogging over. I diconnected hear hose to waterpump to check for airlock, Is there a good way to remove an airlock if there is one ?, All out of ideas, also is there a way to check the heater controls, the hot-cold temp control seems to turn very easy. but it seems to be working.
thank you

 

when at opertating temp r either of ur heater hose hot?