My truck when first started runs up to about 80% of gauge then drops back down like its taking the thermostat time to open. Once it drops back down, maybe 3 miles, its fine the rest of the time. The radiator doesn't build any pressure but I'm not losing any water to indicate a leak. I replaced the cap a and it didn't change anything. Is there any way to tell if maybe the pump isn't pumping, but wouldn't that cause an overheat condition?

As a side note, I can't find a lower radiator hose anywhere local. I'm having to order one, that's frustrating!

 

Try running your heater on full during that 3 minutes....does it keep or drop the temp? If so then water is circulating. Sounds like maybe thermostat is sticking.

 

Heater doesn't effect it either way. I think this weekend I'll flush the radiator and change thermostat to see if it changes anything.

 

Depending on how long it's been since the system was flushed, your budget, and your location.... I'd consider taking it to a rad shop or repair shop that is COMPETENT with using a flush gun to clean your whole system.

Many people complain the Dodge heater cores suck. They work extremely well when kept clean. By doing a true flush with a water+air flush gun your cooling system will work like new. If a OEM Dodge heater core is NOT capable of roasting you in a Dakota, it's not working like it should LOL

Just make sure your parts are in decent shape and the person flushing the system knows how to do it right without making your heater core suddenly be slightly round-ish with burst joints. They also need to remove the heater control valve in the heater line (if your truck has one) to prevent damaging it.

Don't use a cheap thermostat either, when you take them out of the box you can see the big difference. Stant makes a fairly decent one.

 

I just replaced the heater core because it ruptured. It seems that after having a new radiator cap for a week its starting to function normally. I still want to replace the lower hose because I'm thinking it may have something built up in it. Its so hard to the touch you can't collapse it at all with your hand.