Truck is a 1997 4.3 4WD with about 160K. Recent purchase. Have been gong through and fixing all the issues, chaging all fluids, etc. Latest project was the truck not getting to opeating temp. Most it would get is 160 or so. Have been chasing a rough idle and poor mileage and hope this is it. Have also taken off the throttle body and cleaned throughly, cleaning sensors, etc. New filters all around. Anyway, today I instaleld a flush kit, flushed the system, and replaced the thermostat and ECT sensor. Seems to have fixed the problem as it is now running at about 200 or so. I'm guessing it was the thermostat but the ECT is right there and was only like $12 or so I figured why not.

Now the heater doesn't seem to be working. Blower is fine but it is not blowing hot (or very hot) air. Seems the opposite should be true and it should work better, no? Feeling the heater hoses that go through the firewall, one is hot, the other not so much. So the question is, where is the heat going?

The other question I have, after backflushing the system, it would be mostly full of water right? I topped it off with antifreeze but I know I'm nowhere near 50%. How does one accomplish this when using a flush kit?

 

Drain the radiator after using the flush kit and add antifreeze to the remaining water. Takes about a gallon and a half to get back to 50/50. As to your heat: disconnect the hoses going to your heater core and go back and forth between the two with a garden hose - try to get it running freely. You may've plugged it with crud from the block. Don't be tempted to try a high pressure car wash hose. But first remove the radiator cap and make sure the system is actually full, Blazers can be challenging to get all the air out.