DD15 Coolant Question.

It has been my experience that a truck that is equipped with silicone coolant hoses will have a water evaporation rate of some where around 1-2 quarts every few months or when due for service. I think this amount can vary slightly depending on the number of heat cycles and the run time. IMO if you are adding more that a gallon a month, you have a leak somewhere.

A truck with all rubber hoses and no leaks, should technically use near zero.



Pressure test the system where stone cold and put clean dry cardboard under the truck. 9 out of 10 trucks that come through my shop with a coolant loss complaint have external leaks that are just not in a spot that is easily noticed. Dont forget to check inside the cab heater core(s), fuel tanks, apu's.

 

If you have an APU, the leak may be coming from it. Some APU setups use coolant from the truck.

Every time you stop driving, look underneath your truck for leaks. Do you smell burned coolant while driving? Also, the coolant may be leaking inside the cab through the heater core. My heater core is located under my glovebox.

 

Radiator Pressure Test