Dealing with a 2018 Duramax Coolant Reservoir

I've spent plenty of time under the hood of my truck lately, mostly because my 2018 duramax coolant reservoir started acting up out of nowhere. It's one of those parts you don't really think about until you see a puddle of orange fluid on the driveway or, worse, that annoying "Low Coolant" light pops up on the dash while you're hauling a heavy load. If you're driving an L5P, you know exactly what I'm talking about. These trucks are absolute beasts when it comes to towing, but like anything else, they have their little quirks that can drive you crazy if you don't stay on top of them. ...

February 18, 2026 · 7 min · Carlyon Mulhern