92 chev astro van heater won't heat

It is probably not the heater core do to most times when the heater core goes bad it stars putting water into the interior of the car. It may be the heater core supply valve or the blend door actuator is not working. Try warming the Vehicle, then carefully feel the heater hoses, are they both hot? If one is cooler than the other, You need to flush the core, or do a replacement job on the heater core. Also if the system has a heat control valve on the heater hose, make sure it is working! Also check the thermostat, and the temperature blend door, thats under the dash, in the heater plenum. You can flush this yourself, buy the prestone flush kit and install the tee in the heater return line. Disconnect the heater hose at the waterpump, clamp the hose in back of the tee you installed and back flush till it runs clear.20 mins or so.

Blocked air intake to system?

If the heater valve operate properly then the line to the heater core is plug.
Check & replace or flush.

Good luck

Mai

Feel your heater hoses. If both are hot, the core is circulating. If only one is hot-poor or no circulation of the core.
If the heater core is circulating, the temperature blend door may not be working to let blower air pass across the heater core, and into the vents. If vacuum operated, watch the vacuum valves as you move heater controls-you may spot the problem. Check that the vacuum line from the engine to the control switch is working and still connected. If not operated by vacuum, the controls may have cables to the heater case or may be electrically operated. You'll just have to scope it out. Good luck.

make sure when you put in fluid that you burp heater core might be air in it.

If you have two heater cores on your van, the front heater core may be stopped up by rust or stop leak if any has been put in it. It is a common problem i have seen. or your blendoor

the problem is probably the heater core, it can become clogged with dribris. this stops heat from the engine getting to it and then no heat.

It sounds to me that you may have 2 problems. 1). Air Lock in the Heater Core. 2). Inactive Heat Damper in the Plenum.

But since you state that the Heater Hoses do not get warm that is indicative of an Air Lock in the Heater Core. This is a relatively simple fix. It is best performed COLD but requires a method of pressurizing the Cooling System. All reputable Auto Parts stores Sell and/or Rent Pumps that temporarily replace the Radiator Pressure Cap for Leak tests and curing Air Lock. The Collant Level must be filled FULL then pressurized and then loosening the Highest Heater Hose at the Firewall so that Air and a Small Amount of Coolant escapes. Once all the Air has escaped tighten the Heater Hose Clamp, remove the Pressure Pump, Restore the Collant Level to FULL, re-install the Pressure Cap and Start the Engine. As it Warms up you should be able to feel coolant running through the Heater Hoses and they should become warm.

Get the heater core flushed if youy can verify that the valve in the upper heater hose moves when you go from hot to cold.

SOUNDS AS THOUGH THE HEATER CORE IS PLUGGED. TRY BACK FLUSHING IT AGAIN. IF YOU STILL GET NO FLOW IT IS MORE THAN LIKELY PLUGGED AND WILL NEED TO BE REPLACED. THE TUBES ARE VERY SMALL AND PLUG EASILY WITH RUST.