Hope someone can clue me in on this one. Checked the search and there is nothing there.

I have a 2000, Ram2500 4x4 with V10. Losing coolant at a fast rate...approx one gallon per month. So far trouble shooting has included replacing radiator cap, water pump, thermostat, thermostat gasket, and clean and flush radiator.

Cooling system has been pressure tested, resulted is success...system holds pressure. Checked cooling system for combustion gas...negative results on gas in the coolant.

Oil is clean and Antifreeze is clean...neither is cross contaminated from the other.

Vehicle does not leave antifreeze pools, puddles, or droplets when parked while idling or while ignition is shut down.

Heater core does not smell of antifreeze either.

Only location that I have been able to find any sign of coolant loss is from the overflow tube leading from the coolant overflow tank.

Any suggestions on where to look next????

 

I know you said the system was pressure tested, but this coolant has to be going somewhere. Really IMHO sounds like a cracked head, which I believe is a common problem with the V-10.

 

Original thoughts were the same.

Pressure rating on system is 16 PSI...we went 5 PSI over and held. When that was supported we went for combustion gases in cooling system.

Wouldn't one of the two or both tests shown a cracked head?

 

Was that with the truck running or off?

 

Any white smoke out the exhaust?
You can pull the spark plugs and inspect. Usually you have a fuzzy white powder on the tips if its burning coolant.

 

No white in the exhaust. Truck was running during combustion gas checks. We ran pressure tests with vehicle running and shut down.

Spark plugs haven't been checked yet...will have to look at them tomorrow.

 

Update...pulled plugs and they are normal.

Added another gallon of coolant...last gallon was put in during Jan.

Is there anyway that the coolant from the radiator could be moving into the block faster than the thermostat will allow resulting in a backup in the coolant tank? Could the pump be pushing water thru the system to fast resulting in a backup?

 

Is it possible you are leaking from ahose in or around the exhaust manifolds, like say a heater back flush spot? I've heard of guys having a leak they can't find because it's small and drips straight onto the manifold and evaporates.

 

Very strange. If you have to keep adding gallons that's a serious problem.
It can't go very many places. If its leaking in that quantity you would expect to see puddles underneath.
Other than an external leak there are only so many places it can go.
Into the crankcase (and you will have a chocolate milkshake for oil.)
Transmission (and you will have astrawberry milkshake for oil) less common
Or your burning it in the combustion chamber.

Do you have a sweet smell in the cab or under the hood when the engine is hot?

 

I don't smell anything in the cab. When vehicle is idling there is no smell of coolant outside of vehicle or under hood.
All fluids are clear, just changed oil and serviced tranny...all clear.
The onlycoolant that I have been able to find is the from the overflow tube itself after driving in from the house to work (15 miles). Wife smelt a hint of antifreeze in the morning a little over a week ago in the first 7 miles of trip into town. Smell stopped.

I'll have to check the hoses that aim4squirrels mentioned...never thought of a pinhole leak in the heater hoses.