2007 LBZ overheating really bad - Chevy and GMC Duramax Diesel Forum
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post #1 of 4 (permalink) Old 07-07-2019, 03:50 PM Thread Starter
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2007 LBZ overheating really bad

I’ve been watching all the videos and reading about the strange behaviors these trucks have with temperatures. I still can’t figure out what is wrongs with this truck.

1. The truck is used for spraying and injecting meaning it has huge tanks on the back full of liquid. It also tows a dump trailer at the same time.

2. It has done a great job in the past even with this aggressive load... but then last week I get back to the yard and the tech who was driving it informs me that both the trans and coolant were sitting just about 300 degrees.

3. I immediately just do a service on the truck. Trans fluid change, coolant flush, oil change, fuel filter. I take the truck out (~90 degrees outside) with 1 of the 200 gal tanks full and no trailer. It runs awesome on highway and around town, but I try to drive up a hill and about 1.5 miles up it starts getting hot starting w coolant and trans quickly behind it. It hits 235 on trans temp so I stop to see what happens. The coolant immediately boils over. I turn around and coast back down hill and it all goes back to normal.

3. My list for next to try is replace water pump, and thermostats with low temp mishimoto (truck is only used in summer), new radiator cap and then a new fan.

4. As side notes the truck only has 90k on it. It also just idles and drives around slow about half the time for using the sprayer on the bed. This made me think I should check the intercooler for oil, has anyone seen this in these trucks?

5. Thanks so much for all the help,
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post #2 of 4 (permalink) Old 07-07-2019, 05:49 PM
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Did you ever hear the fan go full lock for a cool down?

And the life you describe sounds like it's in a field all the time. Which is not a good scenario when it comes to clogging up the cooling stack out front.

Not talking about what you see thru the grille, this grass and bug buildup will be sucked in from the bottom and collect/mat up on the fins, in between each coil, blocking the air flow thru the stack and to the fan clutch.

If the heat doesn't hit the fan clutch, it's not going to know the house is on fire and lock up full howl (which should immediately drop the ECT gauge).

In order;
clean the stack, then try to duplicate. Easiest way is to drain and remove the radiator, leaving the CAC in place.
It's a common thing to see after years of service.

Once you've verified the stack is clean and flowing air and the problem persists, If the fan never kicks in full lock, then look at replacing the fan clutch.

If at that point after cleaning the cooling stack, the condition persists and the fan is working, then look to the T-stats sticking open as a cause.
replace with new 180/185 set.
Going lower won't fix the problem and will make the truck use more fuel.
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Last edited by Hook'em_Horns!; 07-07-2019 at 05:53 PM.
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post #3 of 4 (permalink) Old 07-18-2019, 02:17 PM Thread Starter
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SO...after trying all of this and only getting minorly better I took egr apart. It was toast so I replaced the whole system. Then it gets a bit better, and shortly there after starts leaking coolant. I found a bad hose, but that wasn't the only thing leaking now. Passenger head gasket is leaking in the back. FML, this is going to be fun.
Thanks for the help!
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post #4 of 4 (permalink) Old 07-18-2019, 04:59 PM
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Welcome to the headgasket club. That could explain the higher temps as well since cylinder gases are probably directly contacting the coolant. You sound like you run on the heavy side so theres probably a LOT of heat being soaked directly by the coolant.

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