Luke L

2021 Sierra 3 liter AT4 10,00 miles, almost always smell coolant after it is parked. Found a couple puddles at 2000 miles and took it in and the dealer could not find anything and pressure testing didnt leak down. I only had a small puddle a couple times when it was run at 25 below zero and then pulled into the shop for the night. Puddle was found in the morning after it had sat overnight. My coolant overflow is almost empty again at 10,000 and it is going back in to the dealer. I put it up on my lift and you can see a coolant trail on the tranny cooler lines on the right side of the motor. The turbo is just above this location and I don't believe the dealer wanted to dig that far into it to fix the leak. Hopefully they take care of it this time.

I have 3900 miles on my 3 liter Duramax and have towed roughly 800 miles with it. 700 miles with a 5500lb trailer load and 100 pulling a fishing boat. I have used 7.5 gallons of DEF so far. I was going to take it into the dealer and complain about the DEF usage, after talking to the dealership owner who returned my call I decided to cancel the service appointment and run the truck for another 5-10,000 miles and monitor the DEF usage. I was told that higher DEF usage is normal while towing and breaking in the motor. Initially I was figuring 5 gallons per/oil change, which is what I was told to expect when I bought it but that apparently is with no towing. Price per mile is more than I was expecting but it does pull great and I made 11 to 12 mpg pulling a 5500lb trailer at 70-80mph. I will wait to see how the def usage is after the truck has 10,000 miles on it and go from there. I average 16-21 mpg in town all depending on how I drive it. And have gotten 23 on the highway at 70mph.