Yeah - I made a joke of it at first. But it could cause your heater core to leak.

The heat was weak first time I turned it on this season. I figured I had the GM Red plug in the heater core. When I got to dad's, I checked the coolant. Clear, dark, greenish, NOT RED.

???

I got home and and got a flush-on. The radiator drained alot lighter green. Then I put the hose in the heater core where there's a 'T', with one line goin' to the TB (or the intake manifold below it) , and pulled the trigger. I heard the water slow, then release pressure.

I could hear the hose water flow, then slow, then break free with the Campbell's chunks in the heater core. Comin' out from the 'T' and the radiator drain was good stuff, then it got darker, and I could feel the chunky jam hittin the back of my hand in the coolant comin' out of the 'T'.

So the heat that I had was not much more than 'interface' with the main system flow. The plug was not the pinkish-white slime plug that you get from GM red stuff.

So the question was, is there a flow controller to the heater core in a '94? Since there is then, when is it open? Always when the heat is on? Only when the heat is on max?

If there's a heater control valve in theheater coreline, that is closed all summer, isn't every car gonna' get jam accumulatin' in the heater core?

If ya' put in a by-pass to allow 'always' flow, ain't ya gonna' get better coolin' in the summertime (and I had no coolant problemsthis summer). Will the heater core heat increase the interior temps, when the heat is NOT on?

EDIT:
Next question: have you ever seen the heater valve controller? If you feed the garden hose into the heater core line, can you break the valve door with water pressure in the line?

OR, maybe the door doesn't completely shut off the flow, so you can't break it, AND it allows a little flow ALWAYS, which [supposedly] prevents plugs formin' in the core???

And, where does the thermostat control flow for? The heater core? So there's redundant heater core flow control?

In short, if your heat ain't burnin' yer little finger in the dash heat ducts, you got flow restriction.

 

I'm not sure just what year it happened, but I recently found out that my 2001 does NOT have a heater control valve. At some point, they did away with them. Bottom line, this means that warm/hot air is ALWAYS existant in your heater core as there is nothing to stop it as it is part of the overall system.

The (sole) device keeping heat out of the interior is an electronically actuated door that (hopefully) closes when you need a/c and prevents the heat from the heater core from coming inside. Your model year may or may not be involved with this scenario.

 

Yeah, makes sense there moscooter, but what was it for in the first place - exactly how did it work even?

And the duct doors must have pretty tight insulation there, with 230* coolant movin' through there in the summer...

I think it was continued on some models by GM. I bought an '02 1 ton Express van, that had one, and which got fouled by GM red coolant, OR, went bad, at around 160k (and I had flushed the thing at 150k).