Blocked heater core?

[Zoro]

My heater has been acting up for awhile blowing cold randomly. Never thought anything of it until I was under the hood with the motor running with the heat on and noticed one of the lines from the heater core was cold to the touch while the other, closest to the engine, is hot. Diverter valve is there and working. I'm guessing the core is clogged. Any good way to unclog it without pulling it? Will compressed air work? Going to be putting a new radiator in within the next month and gonna do a hardcore flushout then of the entire system.

[eaglefreek]

I would confirm the valve is working properly and then try to reverse flush it, flush it in the opposite direction of flow. I wouldn't use compressed air just a garden hose and try to keep from putting too much pressure on it.  You do run the risk of loosening rust and causing a leak.

[IowaEagle]

Install a flushing tee which accepts a garden hose.  As mentioned, reverse flushing with some of the chemicals provided on the market may cause a fragile core to leak.

[Zoro]

Will give that a shot.

BTW, in case I have to how much of a PITA is it to replace the heater core?

[IowaEagle]

Here the article in our Eaglepedia  http://amceaglesden.com/guide/index.php?title=Heater_Core_Removal

[carnuck]

It's a real PITA with one arm! But I did it. First make sure the vent flap under the dash on the passenger's side isn't opening on it's own (right above where the passenger's left foot would be) Mine did that and frustrated me after I changed the core till my buddy crawled under and felt the cold air, shut the flap and the heat started pouring in!