I have an 09 Dodge Ram 1500 that has been having a coolant issue that my dealer and I can't track down.
Truck Background:

• 3 Owner Truck - I'm the 3rd owner
• Over 7.5k engine hours
• 198k+ miles
• Camshaft and lifters and rollers replaced 10k miles ago
• Left and right heads removed and machined and reinstalled @ camshaft replacement

Symptoms:

• The overflow tank/expansion tank will empty itself after a day or so from being filled.
• The radiator will be about 1/2 or 3/4 quart low of coolant.
• The top radiator hose collapses on itself when engine is cold
• The radiator cap is a tight seal and hisses when opening as air gets introduced back into the system.
• The coolant today as turned a rusty color, will see through but brown instead of Neon Green.

Checked:

• Oil; not milky and nothing diluting it. Levels decrease on their normal rate as expected in a 10 year old truck
• Left radiator cap off and revved the engine, no reaction. Head gasket seems fine.

Replaced:

• Tried three radiator caps, all three appear to be working as designed
• Replaced the heater core due it being clogged.

Since the coolant is not leaking into the oil, is not pooling on the floor, and does not smell like it's burning off the exhaust system, I'm trying to figure out where it is going. I have a feeling that it leaks out only at high pressure when the system is hot. Either a hose expands too much and it leak around or I believe the radiator has a crack because it would allow for the coolant to leak or spray out when hot and then when cooling down it would reseal and cause lower coolant levels and a vacuum on the system.

Does anyone have any thoughts on this? I would love to get this figured out and sorted out as I want to use the truck in the summer for towing and don't want to risk overheating.

 

Get a cooling system pressure tester, your local parts store will likely rent you one.... pump the system up to 16psi, and see if anything starts dripping.

 

How old is the water pump? The top hose should not be collapsing.

 

Water pump is probably around 2 years old. It was replaced while the previous own was tracking down a noise. There is nothing around the weep hole that I have seen.

 

That much coolant loss means it's going somewhere fast.....probably out the tail pipe if it's not on the ground....it sure isn't evaporating.

 

If it was leaving through the tailpipe, wouldn't I then be having misfires, coolant in the oil, lots of steam out the tailpipe and other engine issues and overheating?

 

You got a leak somewhere. I would do the pressure test on it and see what you find.