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Discussion Starter · #1 ·
Overheated truck, DIC said low coolant, 1.5 gallons low. Got system all filled up again. No fluid on ground or in oil. Exhaust is good. Top radiator hose is soft when hot. That tells me no pressure, but where did the fluid go? 1800 miles from home.
 

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Welcome to DieselPlace
Please tell us about the vehicle ( Year, Make, and Model ) and list any mods. (y)
 

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2005, 200,000 miles, no mods
I have the exact same truck, the exact same issue when I drive it on long hauls pulling or empty. efi live 24/7 only on level one, RV program designed to not blow smoke at any of the five settings. Injectors are spraying factory fuel amounts on level one.

Unburned gases and unused fuel have been deactivated to not go back into the engine through the intake, however the system is still in place, but closed off and non functional through efi live programming. That said, I believe the radiator fluid is leaking through the hidden hose piece of the EGR set-up hidden to the eye at such an insanely small amount, and at a high temperature, there’s never any evidence of a leak, except I can ALWAYS smell sweet antifreeze on these trips.

I will buy an EGR delete kit some day that eliminates the system altogether. I have yet heard of any other explanation about where the coolant disappears to. Furthermore, apparently the 2005 has the smallest cooling capacity as well, which, with the factory turbo inlet pipe creating more heat and all the stacked on top of each other cooling radiators for everything coupled with the smallest engine cooling radiator the whole package put together slowly heats the engine compartment up hotter and more hot by the hour traveling along long distances is what I read in an informative article about heat build-up.

And for the record I’m not a mechanic and I have little to no mechanical skills per say. Just dealing with the same issue you are, but only on long trips over the road in the summer. Perhaps someone has the answer to the mystery.
 

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It might be worthwhile to put some fluorescent dye in the coolant system and trace down any leaks with a blacklight
 
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Discussion Starter · #6 ·
Mechanic said system has good pressure and no visible leaks. May be internal. If that's the case what am I in for? Obviously it's not a fast leak so do I gamble and drive it home, another 3000 miles or pull the plug and purchase a new truck?
 

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pull the plug and purchase a new truck?
NO. You sound like you've been getting advice from a dealer. ;)

You need more information to make an informed decision, such as how fast it's losing coolant. Start paying attention to that, now that you've refilled and know there's an issue someplace. Keep driving, watch the fluid level, watch the temps, check hoses as you've been doing, check oil for any signs of coolant, etc. Everything you've been doing, to see if there are any symptoms that might help direct you to the leak (or not).

At some point, get a second opinion from a different mechanic that is familiar with the Duramax. Maybe don't even mention you've taken it someplace else already. See if they can find the leak and/or have any other suggestions. Then go from there. You can do a WHOLE LOT of diagnostics and troubleshooting for the price of replacing the entire truck!
 

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Discussion Starter · #8 ·
I came up with the same idea. I'll be putting 500 miles on the truck by Friday, so I'll have a good idea what kind of leak I have going on.
 

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I have the same truck (2005, no mods and currently 215,000 miles). Back around 150,000 miles same thing was happening to me (losing coolant, no sign of it in oil or on the ground, top radiator hose was soft after sitting overnight). Turns out it was my water pump. Mechanic went ahead and replaced head gaskets at the same time (didn't help that while pressure checking system he finished them off and coolant went into oil). If yours is the water pump as well, my recommendation would be to drive it home and check the oil at all stops (oil will look like chocolate milk if coolant gets in, at least mine did) and refill as needed. Good luck and safe journeys.
 
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