Yes it has a rear heater for the farthest back seat. Not sure if it has a separate heater core? If it does have two heater cores where would the second be located?

 

It's back there somewhere, as is the plumbing for it.... So, another place to check for leaks/seepage.

 

How badly? The 4.7L does not take kindly to overheats, not that any engine does but this is aluminum heads on a cast iron block.

 

Got it!
Pressure tested again at 15lbs with UV Dye twice and let it bleed down for 4 hours. Came back and hit it with a UV light and bingo. Not any of the thought issues. I came to be a minor issue. The overflow line where it goes into the over flow tank has a leak. Off to the parts store in the a.m. for a replacement hose. What a relief. No other leaks detected.

Thank You to everyone! I will let you know if this is not the end to this issue.

 

Ya just gotta love the simple fixes.

 

Leaks are gone the Durango is now over heating at speeds lower than 30 MPH and when idling with AC on?

Any Ideas

I am thinking of flushing the system not sure if I want to do the full system regular flow flush through the entire system or to back flush the heater cores it has two. For some reason I am getting no heat to the drivers feet. Not sure what to think of this? Heater cores need flushed? The blend door is broken? Any ideas?

 

Did you bleed the cooling system? Raise the front end and run with radiator cap off, topping off as you go along. Also check to see if your fan is working.

Another thing. Glad you found it, but you didn't find that overflow leak by pressure testing. A pressure tester's cap replaces the radiator cap and has no path to the overflow, else it wouldn't build pressure. The overflow is never pressurized anyway. Last time I checked, coolant glows under UV light without the need for dye. At least the green stuff does.

 

I have did the burping of the cooling system a couple of times. I will do it again may have got some air in it from drawing down the the over flow tank? Just glad to find a leak and now it holds pressure, You are right about it not holding pressure in the over flow. I think you may be right ab[out the UV and the coolant as well. Thanks for the help.

I am going to flush the system and burp it again as well hoping this takes care of it.

 

Just make sure the front end is higher than the rear when you burp it. Turn temp dial all the way hot. (Might not matter as I don't think you have a valve, but it doesn't hurt)

 

Isn't there a bleed valve somewhere on that cooling system??