Short answer
In engines with wet cylinder liners, liner vibration creates tiny bubbles in the coolant that collapse against the metal and can pit it over time, eventually letting coolant into the oil. The right coolant and inhibitor level protect against this. Conventional coolant needs regular supplemental additive (SCA) testing; extended-life coolants work differently. Follow your engine maker's coolant specification, and do not mix types.
Start with the easy checks
- Know what coolant type your engine maker requires.
- Test coolant condition and inhibitor level on schedule with the right test strips.
- Do not mix coolant types.
Likely causes, most common first
- Depleted inhibitors
- Coolant not tested or maintained.
- Wrong coolant for the engine
- Some makers specify nitrite-free coolant.
- Cooling system problems
- Air in the system and low pressure can make it worse.
These are common causes, not a diagnosis. The same symptom can have a different cause on your engine; codes, tests and your service information decide.
When to stop and see a diesel tech
- Coolant in the oil or oil in the coolant.
- Unexplained coolant loss.
Questions
Do diesel pickups get liner pitting?
Cavitation pitting is mainly a concern for wet-liner engines, more common in heavy-duty and equipment engines. Check what your engine uses and follow its coolant spec.
Related symptoms
My diesel is losing coolant with no visible leak. Why?
Troubleshoot →CoolingWhy does my diesel run hot when towing?
Troubleshoot →Guides & checklistsWhat maintenance does a diesel need that a gas engine does not?
Troubleshoot →Where this comes from
- Detroit: Coolant requirements for engine cooling systems (PDF)
- Shell Rotella: Understanding engine coolant types
- ALS: Coolant formulation and cavitation
Last reviewed 2026-10-19. General information only: confirm with your service information and a qualified diesel technician.