With a 19-year track record under its belt, it’s safe to say the Duramax is one of the more reliable diesels to ever grace the ¾-ton and larger truck segment. Sure the LB7 had injector problems and the LLY’S ran hot, but by and large the 6.6L V8 holds up remarkably well—regardless which generation engine it is. We’ve even seen well-maintained Duramax mills accumulate more than 700,000 miles without needing an overhaul or any other major repair. But while the Duramax is no stranger to racking up hundreds of thousands of miles, it’s not immune from requiring a minor repair from time-to-time.
Following the purchase of a high-mile ’06 Chevy Silverado 2500 HD, the truck’s new owner noticed the LBZ was low on coolant. The cause? The 13-year-old, 251,000-mile factory water pump was on its way out. After getting a quarter-million miles out of the original water pump, it was an easy decision to stick with an OEM unit. And thanks to Merchant Automotive’s water pump kit, not only was the owner able to start over with a genuine AC Delco unit, but the new pump was modified to hold up to elevated rpm and higher horsepower. If you plan to keep the water pump alive in your modified Duramax, look no further than Merchant Automotive’s Tig-welded unit.
Jake Bosie of Flynn’s Shop in Alexander, Illinois would handle the 5-hour water pump job. He got started by pulling the passenger side inner fender well in order to access the bottom radiator hose.
With water pump failure striking anywhere between 130,000 and 250,000 miles on a Duramax, we’d say the factory unit on this ’06 LBZ had a pretty good run. When water pumps fail due to age or miles, it’s typically the fault of a worn pump seal, which in turn allows coolant to leak from the weep hole located on the top, gear side of the pump. Maintenance-savvy owners will typically spot a coolant leak before the “Low Coolant” message appears on the dash.
Due to the Duramax radiator not incorporating a drain plug, draining the engine’s coolant can be a messy job. Using a piece of cardboard, wedged between the frame and radiator hose, Bosie was able to minimize the mess by deflecting coolant into a 5-gallon bucket.
Next, Bosie turned his attention under the hood, removing the transmission control module (TCM), the twopiece fan shroud, and the fan clutch. Then the serpentine belt was pulled and the camshaft position sensor was unplugged (shown).
From there, the fan hub was unbolted and the ½-inch rubber hose that supplies coolant from the bypass tube to the turbocharger center cartridge was removed (arrow). Brittle and deteriorating, Bosie would end up replacing the ½-inch rubber hose later on.