Failure mode - Ford 6.0L Power Stroke

EGR cooler failure

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

Symptoms

white, sweet-smelling smoke from the exhaust on acceleration or at idle
coolant loss with no visible external leak
bubbles or pressure build-up in the degas bottle
overheating; low-coolant warning
rough running or misfire if coolant enters a cylinder

Root cause

The factory EGR cooler (square-tube design) fatigues and cracks under thermal cycling. Failure is accelerated by restricted coolant flow from a clogging oil cooler and by degraded / contaminated coolant. It routes hot exhaust gas through coolant; when it cracks, coolant enters the intake and combustion, or exhaust gas pressurises the cooling system.

Diagnosis

chemical combustion-gas test on the coolant (block test)
pressurise the cooling system and look for coolant entering the intake or exhaust
borescope the intake / EGR passages
watch degas bottle for exhaust-gas pressurisation with the engine running

Fixes

install an upgraded EGR cooler; ALWAYS replace or verify the oil cooler at the same time or it will fail again ()

egr-cooler (part category - specific model not chosen)
oil-cooler (part category - specific model not chosen)

coolant filtration and fresh spec coolant to prevent recurrence ()

coolant-filter-kit (part category - specific model not chosen)
coolant (part category - specific model not chosen)

Prevalence

near-universal