WATER KEEPS GOING THROUGH THE ENGINE AND COMES

It usually doesn't matter-it just circulates coolant through the core and returns it. But the hose going to the water pump is the return hose from the core. The other hose from the cylinder head or intake manifold is where the coolant comes from and going to the heater core. Take off the hose at the water pump and you will see a stream coming out with the engine running and the heater control on hot. Try this and if the stream is not good, try swapping the hoses at the core- I mean take the hose to water pump and fit it to the core's upper hose, and the inlet hose to the lower fitting. It shouldn't matter, but let us know.

I don't know if top or bottom, but the heater core inlet will be the hose coming from either the intake manifold or a fitting on a cylinder head. The outlet from the heater core goes to the front of the engine, it goes into the water pump. I think all GM engines are like this, and almost all engine designs likewise. On a 1992 3.8L, for example, the heater core inlet hose comes from the intake manifold on the passenger side. The heater core outlet goes into a fitting on the water pump (lower front of engine).

pretty sure it runs via lower hose, as gravity keeps it in the bottom of rsd.

Old trick with any car ,firstly drain the antifreeze out then refit the bottom hose ,get a plastic bucket and add about a cupfull of caustic soda ,add hot water being usual carefull about this then when the caustic has disolved you add this to the radiator ,then providing the level is ok you refit the rad cap and run engine ,time ? depends say a half hour drive around town ,then let engine cool ,remove the bottom hose to drain being carefull as well whilst doing this .then remove the rad cap and flush it through
,then refit the bottom hose and remove a heater hose ,both it access allows then flush back through the heater hose ,both ways if you can both heater hoses off ,then refit one heater hose and let it back flush out through the rad cap then reverse this flow ,and if it all comes out nice and brown then clears you know your heater will work ,now drive car around with the water in for 5 mins then drain via bottom hose and then after fitting the bottom hose refill with antifreeze 50% min ,even in a frost free climate as the antifreeze is a anti corrosion agent as well .

drain coolant system locate heater cores hoses going through firewall you need to buy the radiator flush kit at any auto parts stores. remove heater cores hoses from one end or buy extra long heater hoses same size as heater core hoses in vechicle at auto parts store use the flush kit when you flush through one of the heater core hoses let the other hose drain in a drain pan when you use home garden hose use low water pressure dont use garden hose to the max or you will rupture heater core. your best bet let radiator shop flush whole coolant system. because heater cores hoses are in a tight spot.make sure engine off if you just going to flush out heater core only .after flushing heater core good time to replace heater core hoses.if job too hard or complicated let radiator shop flush out radiator the engine block and heater core because if radiator stopped up or engine block stopped up the gunk and rust will reenter plug up heater core.if you tight on money you can flush out your own radiator.drain out radiator using large drain pan. remove top radiator hose and remove bottom radiator hoses connect to water pump.use garden hose with flush kit part with water pressure not too high put garden hose to top radiator hose run water until clear water run out bottom radiator hose in drain pan,the flush out engine block remove thermostat.if you had another spare thermostat housing with RTV SILICONE SEALANT THAT HAS SET UP INSTALL THERMOSTAT HOUSING BACK TO ENGINE WITHOUT THERMOSTAT FLUSH OUT THE ENGINE BLOCK, WHEN DONE INSTALL NEW THERMOSTAT THEN INSTALL ORIGINAL THERMOSTAT HOUSING WITH NEW ORING WHICH YOU BUY AT DEALERSHIP.IF ALL SOUND COMPLICATED LET RADIATOR SHOP FLUSH OUT COOLANT SYSTEM.

LOOKING AT HEATER CORE TOP HOSE COOLANT FLOW IN BACK OUT THROUGH THE BOTTOM HEATER CORE HOSE CHECK WATER PUMP BYPASS HOSE SEE IF IT GETS HOT.IF NOT COULD BE BLOCKAGE AT BYPASS HOSE FROM WATER PUMP OR WATER COULD BE FAULTY GETTING TOO WEAK PUMP COOLANT THROUGH SYSTEM.IF COOLANT GETTING HOT GOING TO HEATER CORE THE HEATER CORE AND COOLANT SYSTEM NEED FLUSHING OUT.

sound like you have a clog in heater core or water valve (if it has one ) need to take off heater hoses and make sure it flows thru flush with water hose

it may be a little off, but the lower water hose seldom gets very hot,, as its this hose that suplyes the engine with ""cold water"" the hot water comes out the top hose,, drains down the rad and cools on the way down then enters the engine through the bottom hose """if your engine stayes running in the normal place on the gage,,,and not over heating""" why are you spending money for nothing???""
you wont get the bottom hose to run hot unless the engine is cooking

The engine needs to be running and hot enought for the thermostat to open for water to flow to the heater core. I would keep the top hose on and let the water run out the bottom this will remove any air trap in the heather core.

This problem is one i have encountered on a number of vehicle not just your brand. The problem seams to be in the controls switches and sending units. you have change lot of parts but did you check to see if you had flow through the heater core.Remove the heater hose's from the engine going to the fire wall. This is not precise in how you get the hoses off, however you do it? Once the hoes are off take a garden hose and try to run water throught the heater core. If you do not have a flow you need to find the closed valve. You may need to block off the hoses to the engine so you can run it for a vacume system. You may need to cut and put splices in the water hoses to do this. As a lot of engines you can not get to the end of the hoses.
This is not a simple fix as you would think. As i have found the heater hoses are getting warm or hot with the engine running but it is still cold inside the car. The word is no water flow no heat and if you have flow you have a vent door stuck closed. Air conditioner controls can have effect also. you may also may need to check the water pump out put to the heater core. This needs to be done with all the anitfreeze removed so as not to lose it on the ground. If you do remove the anitfreeze you can check the heater core flow by only removing 1 (one ) hose for the firewall to the heater. if you have hose off remember to put the garden hose in the radiator with it one as not to over heat the engine while it is running. you had heat before it a matter of tracking down where the flow has stop or the cause like a bad switch, broken wire or vacume hose.
good luck