gurgle noise under dash when accelerate

i have a 96 blazer with 68000 miles. a while back i started hearing gurgling under the dash occasionly when i accelerated. i got the radiator flushed and it seemed to stop. (the overflow still had sludge in it though).

a couple of days ago it started again. now it happens consistantly when i accerarate (even in park). this morning it also started making a noise almost like a squesk or a grind...don't know it that is related (i was thinking that it could either be an unrelated squeaky belt or a water pump going bad).

any advice on what to do would be apprecitated. i'm not a car guy so simple answers please. thanks.

Have run into this before-it comes down to low coolant level/leak in cooling system. What your hearing is coolant and air bubbles pushing thru the heater core. Your noise stopped after the flush job because the cooling system was full. Any coolant on a belt will make it noisey-look behind the water pump pulley from the bottom and look for traces of leaks. Hope this helps.