Originally Posted by vwnate1

Okay, almost a great picture, I guess the 'D' hose is out of frame .

So ; I disconnect the A & B hoses as well as the D hose, you'll find that reversing the flow so water is coming out the D hose nipple will often turn cloudy when you put water _in_ the D hose nipple plus of course you want to reverse the flow on the A & B hose nibbles .

The deal is this : sediment collects and settles in the matrix, it's lower than the hose nipples .

Over time this sediment dries out and becomes solid so working it loose it tricky , why I reverse the flow and let it sit awhile each time .

Obviously I've had to learn on some seriously neglected cars ~ some looked great but were allowed to sit a few years, others were battered daily drivers that only had tap water added now and then, all had serious amounts of sediment I flushed out in due time .

DO NOT USE AIR NOR HIGH PRESSURE WATER ! .

The heater matrix is delicate and trust me, you don't want to need to change it out .

Time and patience are your friends here .