2002 durango 5.9L .Is it normal to have to top up coolant every 2 weeks?. No signs of
leaks or overheating and runs well otherwise. Thanks

 

No its not. You might have an exhaust manifold leak. Or some other leak. Park it over a clean piece of cardboard.

 

I have done that and the garage floor is clean. Maybe there is a crack in the reserve
tank.If i don't top it up there is no overheating !

 

You might have a slow leak only under pressure. I had this happen to me and it took me a while to find. Similar problem as you described. It turned out to be the radiator itself. Take a look at your radiator and check to see that the seals are clean and no anti-freeze is showing. Mine went from the lower corners on both ends, but was just barely leaking. You should look into this before it becomes a bigger problem!

 

Is the reserve tank low or you're actual radiator low? Have you checked water pump and hoses? Put a pressure tester on it and check for leaks

 

I don't understand why all the coolant doesn"t drain out altogether even if it is a small leak
bec there is always pressure when the engine is running.

 

Some leaks may take a while to happen under pressure. And they may happen in such a way where you never see coolant hit the ground.. But I would think if you have to fill it every 2 weeks that it is a decent sized leak.

 

There's a leak somewhere... i have had my truck 1 1/2 years and have yet to "top it off"