So I'm trying to back flush my heater core due to poor heating. I've already diagnosed the controls to be working OK. There is an arrow on top of the water valve so I assumed that to represent the flow direction. When I disconnect the hoses and run the engine water flows in the opposite direction. In fact nothing flows out of the valve but the other side gets hot.

Yes, the control valve appears to be working - the cable works anyways.

Anyone have some insight into this? Is that arrow wrong? I mean, that wouldn't make sense, the valve should throttle flow going in. See my diagram below for graphical representation. Maybe my valve is broken?

 

direction of flow does not matter. try bypassing the valve. i also think you have the in and out confused. looks like the hot capped one is the hot comimg from motor to the heater. the other is the return. you wont get any pressure out of the return to flow any fluid into the buccket the way you have it set up.

 

The arrow on the valve indicates the way it should be orientated in relation to the heater core(Heater Core [←Valve]). The flow of coolant through the valve is in the other direction(Heater Core→ [Valve]). So..the valve actually "throttles" coolant going out of(not into) the heater core, and your back flushing method's flawed.

It does if you're trying to back flush...duh

 

your right i was correcting that after a second look at the drawing while you entered your post. my piont was that a heating system will flow in either direction an work, most people will flush in both directions. at first i thought he/she was flushing with an out side source indicated by the blue line (cold water supply).i apologize for upsetting you and making you get all personal on me.

 

Hey thanks for the replies guys. I'm not using an outside supply because it's so damn cold out and I filled the radiator with water and flushing solution. Also didn't want to over pressurized anything.

It sounds like I've got the in and out backwards. And yes, I realize flow direction doesn't matter but I think part of the heater core is blocked because the passenger side is colder but the electricals work fine. I'm hoping that back flushing clears it out.