dakota heater

[flyinlow]

Sons 2000 v6 Dakota dose not get very warm.  Little heat at idle. Some warmth when revved up. I changed the thermostat (205*) No help. I flushed the heater core with the garden hose. A little rust when reverse flushed.

I started the cold engine with the heater hoses disconneted from the heater just a trickle of water at idle , noticably more revved up. V8's I have done this on (440) pumped a lot more coolant. I looked down the tubes with an inspection camera and did not see a blockage as far as I could get. 

Wondering about the pump impeller?  Any though's ?

[A383Wing]

yup, check that impeller, the vanes could have been corroded off