It's a much better idea to replace it. You can try the radiator flush, but no guarantee.
You don't clean a heater core. Once it's clogged, you cannot clean it out successfully. You need to replace it instead.
On a Mitsubishi Galant 2000, an idle on the vehicle could come from lots of things. Changing and cleaning fuel system and its components. Changing spark plugs and making sure wires are clean, rust-free, and tight.
The heater core may be clogged. You would need to take it out and clean it thoroughly. Other things to check are the thermstat
possibly clogged heater core, remove heater core hoses and flush with a hose until clean. reinstall hoses fill with coolant and let it run. if heater core is too plugged up you will have to replace it.
You cannot clean it. If it is clogged it must be replaced.
it's most likely a water flow problem....check the pump filter and clean if necessary. this happened to ours yesterday, and today we found the filter was clogged, cleaned it, and the heater started right up.
The Galant color code should be located on the firewall; sometimes it may be in the driver's side door along the front A pillar. Another possible location is the area near the radiator, where the hood closes. I have an '03 Galant and my color code is located on the firewall passengers side, the 2000 I think is on the driver's side firewall. You may have to clean dirt off of it to see it.
Fault with thermostat Heater matrix clogged (maybe with radiator sealant) That's exactly what was wrong with mine! the workshop had to clean all the radiator sealant (copper) and it start working perfectly.
pore strips
Wouldn't it be easier to buy a new one?
no
clean out the jets and any other holes that are clogged