Heat stopped working HELP!!!

[lilsprite]

I have a 94 astro with a 4.3 throttle body I just put new water pump and thermostat in it runs great but now I have no heat. The heat worked before i changed these thing but now it doesn't. The fan works fine it's just cold air. What do I do?

[CD Smalley]

Does the temp gauge move at all?

I would bet that the thermostat that you installed has failed in the open position....

[lilsprite]

Temp gage doesn't work now either

[tableman]

Sounds like you have an air lock in the cooling system. Did you run the van with the rad cap off, after you refilled it? This allows air to escape. If you have filled the rad right up to the top, you will want to take out about 3 or 4 cups of antifreeze, then run the engine, if you don't do this when an air bubble breaks loose and tries to escape it will shoot antifreeze out the top of the rad.

[drew300]

GM used to be famous for air locks in the heater system. Do these vans have that problem?

[loonytu]

they know to have air lock problems because the engine is lower than the heater core

[Kings-x59]

Let's see, the temperature sensor is in the vicinity of the thermostat isn't it?
I bet you've got an air bubble in the system, right at the thermostat housing- doesn't even have to be in the heater core.
What it means is that your water pump isn't circulating coolant because of the bubble, and your engine is running hot but it's not apparant because the temperature sensor is in the air bubble.
Had this same problem on my Jeep after replacing the radiator hoses.
If running it with the cap off doesn't rectify the situation, unhook the top radiator hose at the thermostat housing. Use a screw driver to Gently open the thermostat and pour coolant directly in till no more will go. Then hook up the top hose.

[brcidd]

You may want to check your heater water shut off valve- underhood right on top of HVAC case- see if it is not stuck in off, bypass position- are your heater hoses hot?

[loonytu]

the heater hoses are hot only going in the valve but not after the valve into the heater core so i am assuming the valve is stuck closed so no coolent can by pass through

[Aqua Angel]

Well i have learned the hard way with my Audi Coupe and my other Audi Sedan and that also applies to Chevy. once you do a coolant flush or any part replacement around the coolant, is to leave that rad cap off until all the air are out of the system. just remove the rad cap, start your van and rev it a few time until you see the temp rise, make sure that you also squeeze the upper rad hose so that you can remove as much air as possible. After reving that engine for 5 to 10 minutes, most of the air should be out of the engine and you will be up and running in no time.

PS don't forget to add coolant when it is getting low.

Good luck.

=D