I have a 2000 Dakota with a 4.7 in it that has recently been rebuilt an doesn't even have500 miles on it. I've replaced all the main things waterpump radiator thermostat bled the engine several times and even went as far as flushing it it numbers times and it's a crying shame I can't drive her why where now! She'll start off just fine for 20+ miles then start to run hot easy ad cutting the heater on I know but she blows out cool air for about 5 minutes then it'll get hot and cut it all off an she'll run perfectly but as soon as you get right into slow traffic she's start back running hot!!! What is a matter with her I'm stumped please help me

 

Who rebuilt it? Maybe it wasnt built correctly? Why was it rebuilt? Were the heads checked for cracks or warpage?

 

I'm curious if your Aux Fan is kicking in? Is it hooked up? Do you still have the Fan/Clutch, does it kick on? (you would hear a roaring sound when it does and you start accelerating)

 

If you've replaced the radiator I would say check the fan clutch. Should roar when you first start up from cold and then subside after a minute or two. When your temp needle starts to creep up higher than normal it should kick into high gear, crack your window so you can hear it.

I've only heard mine come on once when the needle budged over 1/3rd on a hot day during a 5000' climb on a dirt road in the Seven Devils mountains here.

If unsure, they're not expensive and an easy fix.