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best way to clean dirty heater core?

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Mar 14, 2002
seattle, WA
hey all,

A while ago I took a stab at watercooling when I (and my offiicemates) had had enough of the whine of the glaciator. I pulled a heater core out of an old ford escort, and MAN was it dirty. Filled with all kinds of rusty water and gunk. I kept flushing it with water until the water ran clean, and hooked it up in the system. Omitting _many_ details and trials and tribulations, but everything worked just fine until the day the core accidentally took a fall, and on impact dislodged a ton more the rusty stuff to fill up my nice clean tubing.

I'd like to keep using this heater core, but need to find a much better way to clean it. I remember seeing an article on this here a long time ago, but it recommended soaking the entire core in some sort of hcl solution, 'found in many household cleaning products'. The only cleaning products I can find that list their ingredients are basic , not acidic.

So what's the best thing to do? Can I let it soak in a bucket of warm water and radiator flush? Can I put that stuff through my pump (eheim 1048) ? Are there better ways to go about this?

Thanks a lot for any input.

The bucket of flush is 'bout the best idea. You will want to get a pump to circulate the flush through the core. Maybe a power head from a fish tank. Good luck.


Here's what I did with mine...I took a 2 litre bottle, two 1' pieces of tubing, and my pump into the kitchen.

Rinse out the heatercore with fresh water, by sticking one tube up into the faucet.

In the bottle, fill to the label top with warm water, add about a 1/4-1/2 inch of CLR to it. (you can get CLR at any grocery store, walmart, kmart etc..)
Add the two hoses to the heatercore, and the pump on one of the hoses. Fill the free tube (and heatercore) with the mixture, then fill the pump. Plug the open tube into the pump and plug it into the wall (check to make sure the hoses are tight).
Let it run for an hour.

Come back, remove that tube from the pump over the sink, and drain...stick the tube up into the sink faucet (you may have to remove the aerator tip) and run cold-warm water through the whole setup for 5 minutes or so......Done!

It won't harm the pump, and is too dilute to hurt the heatercore.
Rinsing before and after is important, do not skip this!