The 6.0L Power Stroke uses stainless steel injector sleeves to seal coolant from the injector…
Power Stroke 6.0L – Glow Plug Sleeve
Glow plug sleeves are used to keep coolant from coming in direct contact with the glow plugs and to seal coolant from the combustion chamber.
The glow plug sleeve is replaceable. See unique service procedures or the service manual for more details.