On Friday, October 30, 2015 at 8:52:32 AM UTC-4, Terry Coombs wrote:
Hey at least it ain't politics !

Our '99 Toyota 4Runner has a heater problem that's driving me (more) nuts
. The heater apparently isn't getting enough coolant flow , and isn't
putting out enough heat . I've checked all the hoses from the motor thru the
valve and heater core and back to the engine , hoses are OK and the core
isn't plugged . I've also flushed the entire system , all hoses and the core
and associated plumbing . After flushing it out it'll do OK for a short time
then it's back to not enough heat .
Snag

I am stumped too. When you flush the system , do you get anything out or do you just get clean coolant?

I suspect it is just clean coolant. It sounds as if you have something in the line that moves to a place where in blocks the coolant flow. If it were in the engine coolant hoses or radiator , your engine would be overheating.

I would try back flushing the heater and heater hoses. That is have the flushing water going in the opposite direction from the normal flow. If that does not have anything come out of the system , then try flushing the other way and see if there is a good flow rate. If the flow is restricted , then you just need to figure out where. So check the hoses and then the heater core.

I think the most likely place for a clog is the temperature control valve. Probably the hardest place to check.

Dan