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Hi! In Feb of '07 I purchased an '03 1 ton chev. It had over 100 000 miles, but I wasn't concerned as I've heard such great things about these motors. I've had 1 constant problem with it though. Since I've purchased it, it has always leaked coolant. I've sent it to the dealership, and then a few different mechanics. Nobody can figure out what is wrong with it. There are no external leaks and apparently the head gaskets are fine. I found 1 great diesel shop that fixed it for 2 months. But I have since moved to a new state and am dismayed to find that there are almost no shops that will work on this motor. I had the same problem at my previous residence and would be greatful if someone could suggest a good duramax diesel garage in the Phenix,AZ area. I love my truck and think I have gotten almost all the bugs out of it but have had it with this continuous problem and not being able to find a competent mechanic. Please help!:confused:
 

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so you have never figured out the problem with the leaking problem I have the same problem and Im just changing the motor
 

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Thanks

Thanks for the info! My truck has the western hauler conversion and I don't want to get rid of it either.
 

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I Havent payed attention to the tranny coolers on the LB7s and im not sure if they are built in with the radiator or they are separate. Some one inform me on that i would be greatful. But if i had to guess the tranny cooler is separate. But anyways i ran into this problem with a 1/2 chevy it was loosing coolant also not apparent leaks. i pressurized the system it would not hold pressure. Then i just happened to check my tranny fluid, it smelled like coolant and it was over full by atleast a half quart. I never thought that was possible because the tranny line pressure would over come cooling system pressure and you would have ATF in the coolant. But i was wrong the cooling system pressure must have allowed it to seep into the the tranny cooler on the side of the radiator when the truck was not running. I doubt that this is your problem but it maybe one quick check you could do that someone could have over looked, if the tranny cooler is not separate from the radiator on the LB7's.
 

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Pull the splash guard (aka plastic skid plate) down in front and inspect for coolant weeping around the water pump. From my research seems kind of common. I've been told that Dex-Cool will evaporate quickly, so it may not drip and leave telltale puddles but could still be leaking.
As for the other option, head gaskets. I understand about the pressure test, but I've read a better way to tell is to run the truck for awhile (get it warm) and shut it off. If within a couple of minutes 5 or so, if the upper rad hose is still rock hard you've got a headgasket issue. Check the oil to see if it's "milky" or slimy to indicate the presence of coolant, and finally, if after the truck has been shut off for a while, SLOWLY open the cap on the coolant overflow tank. If the tank is holding mucho pressure after sittiing for a while after running, you've most likely got a head gasket even though the pressure test may not indicate it.
Just my .02 from doing some reading on the subject.
 
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