I have a 2000 Durango with the 5.9 engine.
Radiator got hole in it so replaced it. also did the water pump, cap and thermostat at same time.
Now am seeing that the overflow bottle gets water to it but it doesn't go back into the system. I now see hot water coming out at cap as water pressure and heat get to normal. thus resulting in over heating.
Have tried all the tricks to ensure that there is no air in the system. Have checked system with pressure tester and loos no water.
Any ideas, as now can drive it about 10 miles and then have to add water?.

 

Water won't go back into the system until the engine cools. As it cools, the coolant contracts, creating a vacuum in the radiator, which will suck the coolant back in. Do you have the wrong radiator cap??

 

Sure you didn't install that thermostat backwards?

 

Have tried the new one and the old one same results. Can't understand why it starts blowing water out at the radiator cap.

 

Pretty sure, if in backwards it shouldn't circulate the water, right? and it does do that.

 

Did you flush the block and heater core when you replaced everything?

 

It would circulate the coolant already in the block, like cold start. It would never open up to circulate the radiator contents. How do the top and bottom hoses feel when it starts to overheat?

 

If you are running it with the cap off, yeah, when the 'stat opens, it's gonna blow coolant out. Especially if there is still an air pocket in there...... Need one of the neat funnels designed for just such an occasion.

 

Every new thermostat has to be checked in boiling water with old one.

 

I had all kinds of water and heater problems until I fixed the head cracks.
All that stuff works way different now, with all the same old parts....
I suspect the cracks were such that combustion got pushed into the water but water did not leak to pistons sitting.
5 out of 8 cylinders, intake to exhaust, $600 Jegs heads