Failure mode - Ford 3.2L Power Stroke Diesel (Transit 2015-2019)

Coolant loss without an external leak (overheat)

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

Symptoms

overheating with no visible external leak
recurring low coolant in the degas bottle
coolant odor / traces at the EGR or oil cooler area

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

Root cause

Internal coolant loss into the exhaust/oil paths via the EGR cooler or oil cooler seals - Ford documented 'Overheat Due To Coolant Loss Without An External Coolant Leak' (SSM 48543, MY2015-2019) alongside the EGR-cooler overheat SSM 46122.

Diagnosis

pressure-test cold and hot; inspect the EGR cooler and oil cooler before condemning external hardware
check the oil for coolant contamination
trace the degas bottle level history - intermittent loss with no puddle points internal

Fixes

EGR cooler / oil cooler replacement per the found path, fresh coolant, level re-check ()

egr-cooler - more than one option: 3.2L Power Stroke EGR Cooler (CK4Z-9U433-D, current), 3.2L Power Stroke EGR Cooler Valve Assembly (CK4Z-9U433-B)
3.2L Power Stroke Oil Cooler / Filter Adapter (BK3Z-6881-D, current)
powerstroke-3_2: coolant (service item)

Prevalence

common