heater not getting hot

[rstar]

Hello. This is my first post and your help is much appreciated.

Heater output seems to only get hot if the engine is rev'd for 5 minutes or being driven to maintain the rpm's high.
1) Thermostat OK? The temperature gauge reads around the 1/4 mark and fluctuates higher a division or two higher then returns to the 1/4 mark. As I recall it always seemed to read that way. It never was up near the 210 degree mark.
2) Temperature control OK? The temperature control seems to operate in that I can go from the cold to hot position and get cold to warm (and sometime hot) air flow in the truck.
3) Hearter core OK? not sure. Even though I can get some heat, could a clogged core result with the tempermental warm to hot scenario I explained above? The hoses going into the core both seem warm/hot. The output hose is not cold unless just the engine heat convection is fooling me. I tried to pull the hoses off the core to try a back flush, but I didn't have any luck removing the hoses. I was afraid of stresssing the hose connections at the core. Should this be of concern?

Any ideas?

[cgrimm9]

what I would do is back flush the heater core I am assuming that you had dexcool and gelled up in your heater core. take both hoses off your heater core take a garden hose and turn on the water should take care of the problom

[rstar]

Yes. it is a 1997 with Dexcool. Is that prone to clogging up the core? How flimsey are the hose connections to the core? I couldn't get the hoses off and I'm afraid of bending or braking the connectors.
Thanks for the feedback.

[jackass#1]

try to disconect hoses from the other end not from core

[cgrimm9]

yeah I should of been more specific. its easeir and also dont want to break the heatercore

[rstar]

Thanks guys! I'll try it tommorrow morning.

[OverBoardProject]

You should really use something like Prestone rad flush too.
If you have a compressor blowing the system out afterwords will really get rid of a lot more junk.

When you re-connect everything try filling the system through the top heater outlet, and it will fill the heater core... otherwise you'll have an air pocket in there, and no heat.

[footballmoose]

when the water level is low in the radiator it will cause no or little flow to the heater core.sounds like your problem.

[jackass#1]

any progress?

[dblthebass]

check the thermostat it might be stuck open