My heater only blows warm at best, that’s only after the engine gets warmed up good.
I’ll just start with everything I know and hope someone recognizes the problem. Top radiator hose is hot, bottom radiator hose alternates from cold to warm. Engine temp gauge gets up to the middle position after engine runs a few minutes. Engine never overheats. There are no numbers on the gauge, so I don’t really know how hot it gets. One heater hose at firewall gets pretty hot, the other one is cool to warm. However after you kill the engine, both hoses are HOT. I haven’t checked any air doors or vacuumed lines. But it’s getting to the point that the air never comes out of the defrost vents.

 

Vacuum or mechanical vents? (do you have a/c?)

Sounds like the heater core is getting plugged up. Could try backflushing it, and see if anything interesting comes out.

 

I will try flushing it. Do I just unhook the hoses at the firewall? Which is the “in” and which is the “out?
yes I have ac. It works great.

 

The side that's hot is the current "IN". The one that's cold when running is "OUT".

Try flushing OUT to IN first.

It does sound like the core's plugged, or the hoses would go from HOT to STILL PRETTY DARN WARM while the engine is running; the cold side says you're not getting much flow through the core.

To answer HeyYou - Temp is mechanical, all others are vacuum.

RwP

 

Thanks. I’ll try that this event and let you know what happens.

 

Ok. I ran water through the core from the “out” hose. A few chunks of goop came out. I can run water or air through the core. It still feels a little restricted but you can blow through it. It this normal or is it still clogged?

 

Blowing thru it won't really tell you anything.... Just a couple tubes being open will pass air. Running water thru it in both directions several times will clear a fair bit of the junk.... whether that will be enough remains to be seen.

 

Thanks. I’ll let ya know. Dang. All this plastic under here is so brittle. But I guess it is 26 years old.

 

Yeah, whoever thought plastic was a good idea for vacuum lines shouldn't be an engineer. After so long, if you even look at them cross-eyed, they disintegrate.

 

Well. The air in the cabin is warmer than it has been in years!

Which side is the thermostat is the temp gauge on? My temp gauge is on COLD. But I don’t think my thermostat has opened yet. Also. I broke two vaccine lines while I was taking the heater hose off.