Failure mode - Ford 6.0L Power Stroke

Head gasket failure / cylinder head lift

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

Symptoms

white smoke and coolant loss
immediate pressurisation / bubbling in the degas bottle on start-up or under load
coolant overflow, overheating, sweet smell
overheats and then stalls, and will not restart until cooled
misfire; coolant in a cylinder on borescope

Root cause

The factory torque-to-yield (TTY) head bolts provide marginal clamping load. Repeated overheating (usually caused by the EGR / oil cooler failures above) and / or increased cylinder pressure from tuning stretches the bolts; the heads lift off the dowels and the gasket loses its seal. Almost always a downstream consequence of neglected cooling problems or added power without studs. Ford enlarged the cylinder-head alignment dowel from 18mm to 20mm at engine build date 2006-01-16 (Ford catalog gasket application; vendor pages cite 01-11/12); vendors describe the larger dowel as a more robust locating point that reduces 'head shuffle', but there is no published data showing MY2006+/20mm engines fail head gaskets meaningfully less often (SME question).

Diagnosis

combustion leak (block) test confirming exhaust gas in the coolant
cooling system pressure test
running compression / cylinder leak-down
observe degas bottle behaviour at idle and on a road load

Fixes

ARP head studs plus new head gaskets; machine-shop check of head and deck flatness; the gasket MUST match the dowel size (18mm: Ford 4C3Z-6051-EB, engines built before 2006-01-16; 20mm: Ford 6C3Z-6051-AA, engines built 2006-01-16 and newer - Ford catalog gasket application rows). Confirm dowel size by build date, measurement, or head casting number (18mm: 1843080C1/C2/C3; 20mm: 1870389C1); a step dowel (Ford 6C3Z-6B041-B) adapts 20mm heads to an 18mm block ()

head-stud-kit (part category - specific model not chosen)
head-gasket-set (part category - specific model not chosen)

for higher-power builds, O-ringed or fire-ringed heads ()

head-machine-work-o-ring (part category - specific model not chosen)

fix the cooling-system root causes first (oil cooler, EGR cooler, coolant) or the repair recurs ()

Prevalence

very-common