I have been without heat for my 2nd winter now (I know, I know)...and am now trying to do something about it. I am in the process of flushing/backflushing the heater core and am wondering if there is some sort of a solution, or cleanser, or something that I can flush through the heater core to try and help break up any residue or blockage caused by years and hundreds of thousands of miles of buildup. Any suggestions?

 

I would use plain water. If it's clogged up enough where water won't clear it, it should be replaced.

 

I was doing some looking around on the Interwebz the other day and found some other forums with posters claiming really good results with CLR being run through the core.

So, you may want to unhook the hoses and rig up an assembly and pour some CLR in and let it do its job for a while.

 

Petey, I merged your two threads on this topic. Please don't start multiple threads on the same subject - it can lead to confusion.

I vote for plain water too.

- Jack

 

thanks for the tips...here is the latest...I was able to (just using water) flush/backflush just the heater core and see just the vaguest bit of stuff come out after about 20 minutes of this...the heat improved just barely. I have verified that the blend door on the heater core functions properly.

when flushing the core, a fair amount of water comes through in a good stream but I'm still convinced that there is some blockage in the flow. The next step is to flush/backflush with CLR.

I will keep the thread updated and appreciate any and all help.

 

I have the same problem with mine. How did the CLR work out for you? I need to backflush mine just wondering if it worked for you.

 

I just back-flushed my heater core by following "car guy" you tube video. Reversed flow on heater hoses and started with forced air from air compressor. Really did remove some bad looking stuff. Then I poured a bottle of radiator flush in the heater hose and let it set for 30 mins. Blew all that out with air and then added water, again blowing that out. Finally re-connected, topped off coolant and now I have heat. 2002 f150 SC 4.6 V8.

 

I wound up using the CLR. I blew out the old coolant with an air compressor and poured a 50/50 mixture of CLR and water into the heater core hose on the inlet side until it started to flow out of the outlet hose, plugged the hose ends and left for an hour. Blew out quite a bit of scale from the heater core. I then flushed/backflushed the core with water hose several times. This improved the heat but still not fully restored. I repeated the process and left it overnight. Blew it out the next day and got quite a bit more scale and debris out of the core. Improved the heat substantially. I still think it could be hotter but I have heat. I am going to repeat the process again to see if I can get more improvement. I also drained and flushed the entire cooling system (removing the thermostat first) for 5 minutes and then replaced the thermostat with a new one. Refilling with the appropriate 50/50 mixture of antifreeze.

 

Still would love to hear any experience/suggestions of anything else to try to improve the heat.

 

CLR is good stuff, but it needs to touch the calcified areas. If you have a passage in the heater core completely plugged, the CLR can't get to it and won't dissolve it. You can try leaving CLR in for a few days, but really it seems you need to replace the heater core.