schematics and diagrams: How to Unclog heater core?

When dealing with a clogged heater core causing poor or no heat situation, I've had good success doing it myself, for about $25-$30 . First thing to look at is if you can get to your heater hoses, as some may be a nightmare, others are easily accessible, but the closer you can get to the heater core, where the hoses go into the firewall, the better. Many will allow you to remove the heater hoses right at the firewall which is ideal.
With engine cool, I simply remove the heater hoses (after draining down the system and making sure I don't spill antifreeze on the ground where animals can get to it, which if ingested could more than likely kill them), and attach a drill pump, and hose to one of the heater core tubes, then get an extra piece of garden hose, and attach it to the other core tube, and cut it long enough to run it back into a pail, as a return line, to recover the cleaning solution. The hose on the suction side of the drill pump also goes in to the pail. Then add 1 or 2 jugs of CLR, (calcium, lime, rust remover) available at most hardware stores, into the pail as my cleaning solution. With pressure side hose from pump attached to heater core tube, and other hose(suction) from pump inside pail to draw liquid, as well as return hose from core in pail, start up the drill pump, which can be driven with electric, or cordless drill. I circulate it through for a while, then stop and let it sit in the core to work at the calcium etc inside the core for a few minutes, longer the better. After running it through a few times that way, I reverse the hoses at the core, and run it through again, like a reverse flush, and repeat as above, letting it sit in there for a while from time to time. I will normally do this when it isn't urgent that the vehicle be used soon, and if at all possible, I will let the CLR sit in the core overnight just to give it that extra time to break things down inside that core. Then next morning, I will run it through again, and reverse hoses again, run it some more, then I'm done. Remove all hoses, re-attach heater hoses to core, and start vehicle, re-fill cooling system, with heater turned on to remove air in system, and your done. I found this quite effective as well on vehicles that tend to blow cooler air when idling, but get warmer when RPM's are increased, just due to less restriction now in heater core, allowing coolant to flow through better at idle as well as higher RPM's. I've saved $100's if not $1000's of dollars this way, not to mention a lot of aggravation trying to change the heater core. Even if it doesn't get you back to the heat you were getting when vehicle was new, if money is tight, or your just trying to make the vehicle last a little longer before your ready to replace it, this will probably get you the heat you need to get you through until it's warmer outside. If you can't get to the hoses at the firewall location, try following them back toward engine to a location that may be easier to work from. There you would want to buy a couple of "Barbed" fittings (Joiners) the proper size to enable you to cut heater hoses, attach hoses from pump, then re-attach heater hoses together when done. Be sure to get good quality fittings, and re-check for leaks after/occasionally, to be sure. Be sure to check also, that there isn't some type of valve restriction or whatever in the hose between where your planning on cutting hose and the heater core where it's attached, that will not allow flow through, as well as out on return hose. Be sure to store or dispose of cleaning solution (CLR) in a safe place. It does have other cleaning abilities, as labeled on the jug, and a simple coffee filter in a funnel, to filter out the debris from core and poured back into jugs will allow you to re-use it elsewhere, but if you do, please remember it has been contaminated with antifreeze, and if re-used for cleaning or whatever, make sure it's not an application where it may be ingested by animals, or humans. Best bet for safety sake, is to dispose of it properly to avoid that risk.

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