Heater Core Flush!
 

I dont know if this is the right place to post this but I just have a simple question. I want to flush me heater core and heres how Im gonna do it. Im gonna run water through the outlet to flush whatevers clogging it through the inlet. After Ive done this I want to run compressed air through to blow out whatevers left. My question is how many psi should I run through it so I dont damage the fins inside the heater core? Any help is appreciated.

I wouldn't go above 15 psi thats what rad caps are rated to spew @...

air compresses, liquids do not. So 15psi for liquid would be quite a bit higher for air. I'd say 45psi would be reasonable but dont hold me accountable if it goes bad :)

You can't hurt the fins. All your doing is blowing through aluminum tubing. The fins are on the outside of where the liquid runs.

I have never used air but I would recommend flushing the heater core from both sides. I always flush in as many directions as possible when I do a flush. The different direction of water should help to break loose anything thats hanging on a little better. Since your doing it you should flush the entire system while your at it and its also a good time to change the tstat. I remove mine when I do my flush just to make sure its not blocking and debris from escaping.

Just did mine, take 2 hoses off at firewall then spray both ends....

Flushed mine by taking similar sized garden hose (cut) with fittings on either end. Clamp the cut ends on the inlet and outlet ends of the heater core and use another hose hooked up to a spigot to hook to one of the two hoses now attached to the blazer. Turn the water on and run until clear, switch hose to the other side, run until clear. Repeat until water runs clear as soon as it starts coming out of either of the hoses. Then you're good to go!