yamaha894racer

now that it is starting to get a bit chilly here in WI i would really like to get my heat going strong. my problem is heat is weak and not to sure why? truck runs at normal temp and warms up normal. thermostat is working as it should as you can feel the upper radiator hose get hot when it opens. both of the heater hoses are warm( both about the same temp). the heat blows kinda cool when the fan is on high but then and low it blows warm but output is not enough to warm the cab. how ever when i rev it up to about 3000 rpm and hold it for about 30 seconds it will blow a bit warmer on high and hot like it should on low. i was thinking maybe a water pump and the heater core is just not getting the flow unless it is at high rpms. any ideas what else it could be? anything you guys have ran into befor? thanks in advance!

Prayerhater

I am having this exact problem! I thought my heater core was stopped up so I flushed it. That didn't help. So I had the entire coolant flushed. That didn't help. I would love to figure this thing out.

gator0308

Mine did the same thing a couple of years back. It was the water pump. The fins had rusted completely off. Hope this helps

yamaha894racer

would explain the rust in the coolent! thanks ill check it out!

MyFX4Project

Mine does the same thing but I just replaced my water pump, coolant, overflow tank, upper/lower hoses, and thermostat. It was a very dark and ugly brown before I replaced all of those parts.