need help ready to throw in the towel,heat is luke warm and when turn on the fan gets colder,I flushed the system flushed heater core checked blend door changed thrmostat everything seems to do what is suppose to but still no heat

 

Maybe water pump impellers are worn off and not circulating the coolant properly. Does it warm up when it is at road speed?

 

fixed it took the lines off heater core and flushed again but used the draino cleared the core and now have heat, the core was paritally clogged even though water was running through it center of core was blocked up, so when turned on fan only got cold but it is nice and toasty now fixed it with 3 dollar bottle of draino instead of five hundred for new core and install.