Flush heater core?
 

Hey guys. Just curious if anyone has a link to a HOWTO or DIY (prefer text and pictures, but video is okay too) for a heater core flush specific to 6th gen Civics. Thanks!

Re: Flush heater core?
 

Describe symptoms?
Fan on full blast: Weak heater output at idle, but heat gets a lot better with the RPM held high? (air trapped in upper heater hose or core)

Weak heater output regardless of RPM? (water flow or blockage issue)
No heat at all?



Check that radiator is completely full

Check that engine does come up to operating temperature, 180F and above (thermostat)

Check that cable operated lever on the water shutoff valve will move the lever about 90 degrees, as you adjust the temperature control from full cold to full hot (cable housing may dislodge from its clamp and not move the valve a sufficient amount...for testing you could disconnect cable and move valve lever by hand as well))

Check that the same water valve is actually closing and opening the passage inside, it's possible the valve could be broken internally

Check temperature of heater inlet and outlet hoses (engine at operating temperature, highest temperature setting, fan on full blast) feel for temp difference with your hand (tells if hot water is flowing through the core, and indicates how much heat is being removed by the blower fan)



To flush core, I'd disconnect the heater hoses at a most convenient location and then use a garden hose to "jet" through the circuit in both directions several times...be sure to check the water valve is wide open before attempting this

There are more drastic options for when the core is actually clogged with sediment of some sort, such as a HECAT pulsator flush gun, or even pumping something like CLR through the core

Re: Flush heater core?
 

ezone pretty much stated it all...however when i flush heater cores i find it easier to disconnect both in and out hoses leading to the core and flush from the out port with a decent amount of pressure...hey this is messy and a coolant refill and burp is required after but beyond the ONE heater core i actually had to change because this didn't work...just a completely messed up core....the countless cores on all makes and models i cleaned this way worked just fine...this might not work the first time but if you want your heat in the cold cold winters then you do what you gotta do....i never had to do it more than twice