Failure mode - Duramax 6.6L V8 Turbo Diesel (GM HD, L5P 2017+ generation)

Cooling system wear: water pump, hoses, thermostat (towing duty)

Reliability tier: aggregated - verify before ordering, see /disclosure/

Symptoms

coolant seep/leak from the water pump weep hole; soft hoses; temperature creep under sustained tow
the risk is being stranded - vendor framing: routine inspections catch a failing water pump early

Compare with the other causes of the same sign on this engine: losing coolant · overheating or temperature creeping up (2 causes)

Root cause

Normal wear of water pumps, hoses and thermostats at higher mileage, accelerated by towing duty - the vendor guide frames cooling as a wear-item cluster, not a defect. NHTSA VOQ adds almost nothing engine-cooling specific for this platform (1 water-pump mention).

Diagnosis

pressure-test the cooling system; inspect the water pump weep hole, hoses and thermostat at service intervals
rule out the EGR path when coolant drops with no external leak (see the EGR record)

Fixes

replace the water pump / thermostat / worn hoses; refill with the specified coolant ()

Prevalence

occasional