I searched didn't find answer sorry if repeat' 2003 Dakota 4.7 3 weeks ago no heat at idle,did add coolnt about 1 qt to over flow,if revved to 1500 rpm got good heat. Now got close to over heat at idle low speed rpm.When driving home at 65mph no problem,but after slowing for 35 zone got hotter then at 55 started going up again again this is at 1500 rpm,turned off OD engine at 2000 cooled down made it home. 200,000 mile truck. Did find over flow almost empty refilled before going home with above going on. Did find that I spilled some lucus additive on water pump pulley wiped off also. when it was low a wile ago refilled but never bleed it. Thinking water pump with t= stat for good measure and good bleed? thank you all

 

Check the radiator, you are likely low on coolant. Need to find out where it is going.

 

Water pump vanes can wear down causing less flow and overheat. Also sounds like WP is leaking. Grab fan blade and rock back n forth. Should be rock solid. If not, pump bearings are worn.

 

My '02 with the 4.7 did that and I thought it was a leaky radiator. It was a loose water pump shaft. Topped it off and the heat worked great and reliably.

 

If overflow was empty, I assume you filled the overflow container. Did you also remove the radiator cap and check/fill there too? That's even more important than overflow. Check them again and keep checking often till u fix the root cause. 4.7s especially, does not do well with overheats.

 

Thank you all. I never let the temp get out of the bracket on gauge,lite was on for 3 seconds only. Know better then to let a engine get too hot. Coolant over flow has not gone down.snow here and am a old man have a backup car. Could not get cap off hose first try,going to wait so can get at least hose/cap here so if it break's can fix.,if break's or comes off will fix that then see how she act's ,will probably do water pump stat belts hoses etc.If cap, bleeding works may wait a little to do all of it. THANK YOU ALL.