Chrysler Repair: 90 2.5L 4 cyl. heater problem, domestic water supply, haynes repair manual

Question
Hi Roland, just thought I'd give you a few updates on my lack of heat situation. I had a mechanic check it out for me and he said that the water pump and head gasket seem to be okay. He told me that my radiator fan relay needed to be replaced, and he also felt both hoses going into my firewall for the heater core; and showed me that one was "sqishy" like it should be but the other one was kinda hard to squeeze...almost solid. He told me that my heater core seems to have some kind of blockage in it and that I should try a reverse flush on it first to see if that would clear the blockage. If not, I'd more than likely have to replace the core. Well, I've replaced the fan relay which works fine now. I know how to do a flush and a reverse one on the radiator...but I have no clue how to flush or reverse flush a heater core. I own a Haynes Repair Manual, but it doesn't show me how to do a flush of ANY kind on the core; it only shows how to replace one. (which looks like it's gonna be a job for NASA, even with the book) Anyway...do you have any ideas on how to clear out a core???

Answer
Hi Scott,
You would remove the 2 heater hoses where they attach to the engine, and use an adaptor for a garden hose on the heater hose that is the return to the engine side, from the core. Then turn on the domestic water supply to the garden hose and hope it flushes the core well. The adaptor is likely available at an autoparts store; I have an old one that Prestone marketed as a kit to do a cooling system cleaning/flush/etc. You would want to drain off the coolant again to get it lower than the heater core hose attachment levels before you start.
Roland
PS: The input hose is the one that comes out of the thermostat box, the return hose is the one that goes to the water pump. You can access both hoses I believe at the heater by-pass valve near the master cylinder by the way, I believe. Also, you might want to check that valve which is vacuum operated. It requires vacuum on that valve when choose AC-recirc and that is when the valve opens and allow the coolant to short circuit the heater core. If that valve were to be stuck in the by-pass setting that would also explain a lack of heat, by the way. I didn't happen to think of that as a cause of your problem. So check that valve and observe whether it moves when you choose AC/re-circ at the control panel. If not, then it might be stuck in the by-pass position. The lack of vacuum would not cause the problem, only the valve being stuck in that position would.