2001 Chevrolet S-10 • 35 miles

I've read through older posts of simalar issues, and I think I might have an 'air lock', of sorts, in the heater core. Would like an opinion on how to fix this.

2001 S10 V6 4X4 P/U

Noticed a bubbling noise under the dash for the last two years. More prevalent when accelerating. I figured I had a plugged A/C drain and was hearing condensate slushing around in the housing. I never did find the drain, but my cousin, an S10 owner, said not to worry about it. I noticed this past Summer, it was draining A/C condensate as it should, so I assumed it fixed itself, as I no longer hear the 'sloshing sound'.
Well. Now the heater barely puts out warm air.

One of the two hoses is hot, the other is cold, so it seems I'm not getting flow through the core. I traced both hoses down, looking for a "heater control valve". None found under the hood. The coolent level was down just above the ADD mark when cold. I've added about a pint and it hasn't gone down. I can't say it hasn't been low in the past. I always go to Midas for oil changes, so if they added any coolent and didn't tell me.I'd have no way of knowing.

Anyone have an idea where to start?
November 19, 2011.

Check the heater core if its clogged-up

Nov 19, 2011.
Ya OK. That makes sense. Although, not what I wanted to hear as the hose is put up and the water lines to the garage are blowed-out for the Winter.

I assume you meant to try the water flush, as described elsewhere on this site? Right?

Might have to get this done by someone before Spring. : )

Thanks Much!

Nov 19, 2011.
Before working on it, start the engine, allow the engine to warm up to operating temp with the heater on, and feel both heater core hoses. If both are hot, the core isn't plugged. If only one gets hot, then it is.