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 . Pertinent info - the water control valve
is cable operated from the dash along with the gating for airflow in the
heater box . I don't think there's a t-stat type device in there for temp
control , but if there is one and it's malfing that might explain it . The
coolant level is up , and circulating when observed in the radiator .
This has really got me stumped , and the wife is getting pretty hot
herself about it - we're getting into the cold season here and she's the
main driver .


Did you reverse flush it with the heater hose off, or just run water
through the system with it closed?

How fast does it warm up to operating temp?

Grab an IR thermometer and see what the water temps through the system
are. Just look for a large temperature differential to find the blockage.

I'm thinking you have some scale blocking the flow through the core. I
would probably pull the lines off the core, run some Prestone flush or
diluted CLR through it in a closed loop (5 gallon bucket and a drill
powered pump does pretty well to circulate the flush).
Then do the same with the block.

--
Steve W.