I just recently bought another 96 Blazer and the previous owner left a partial jug of green coolant in the back. I must assume that he's been topping the truck off with it. The problem is, when I when to back flush the the heater core, red coolant came out. What i need to know is how do I completely drain,flush and clean every single hose, tube and passage way the coolant sees during its circuit. I, and I'm sure many others would greatly appreciate comprehensive step-by-step insructions on how to do this. So far I've only been able to find summaries of this with no mention of the drain plugs on the engine itself (or their location) and how-tos on just flushing the radiator or heater core. Complete instructions from a knowledgable member would be a serious help. Thanks

 

To forward flush
The heater hose coming from the top of the intake is your engine output or hot side, remove that hose and hook a garden hose to it. turn on the garden hose and let it run until you see good clean water.

To reverse or back flush
Hook the garden hose to the intake and turn on the hose

Both ways work much better if you take out the thermostat and bolt the housing back on without the thermostat

Now to drain out the water, either remove the lower rad hose or use the drain in the rad if equipped, blow out the heater core with a air compressor and don't give it 100 psi that will definitely cause issues, and the engine block has 2 very hard to get 14mm plugs in the side of the block, left side plug is located just behind the motor mount and in front of the oil filter remove the 2 plugs.

Once the water is out as best as you can, reassemble everything and fill with coolant, start it up and bleed out the air

OR take truck to local repair shop and have them hook it up to their coolant flush machine and pay whatever their price is.

Hope this helps ya