Failure mode - Ford 6.0L Power Stroke

Water pump failure

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

Symptoms

coolant drip from the weep hole below the pump
coolant loss; coolant staining on the front cover
whine or growl from the front of the engine
overheating with NO external leak (the classic sign of a spun / cracked plastic impeller: the pump turns but moves little coolant)
pieces of plastic impeller found in the coolant filter

Root cause

Bearing and seal wear over time. The bigger issue is the factory plastic impeller: after years of heat cycling in hot coolant it goes brittle and can crack, fragment, or spin freely on the shaft. When it spins free, the pump is 'turning' but not circulating coolant, so the engine overheats with no visible leak. Reported as worse on 2004.5-2007 build.

Diagnosis

visual inspection at the weep hole and front cover
check for water-pump shaft play
if overheating with no external leak and the coolers/gaskets check out, suspect a spun or cracked impeller
inspect the coolant filter (if fitted) for plastic fragments

Fixes

replace the water pump (units with a metal impeller are preferred); replace the thermostat and degas bottle cap at the same time; refresh coolant ()

water-pump (part category - specific model not chosen)
thermostat (part category - specific model not chosen)
degas-bottle-cap (part category - specific model not chosen)

Prevalence

common