Marine Cylinder Head Repair in Australia
The cylinder head on a marine diesel carries the valves and injectors and seals against high combustion pressures, while coolant passes through it — and on many raw-water-cooled installations, so does seawater at some point in the system. That combination means marine heads fail from corrosion as often as from heat.
Symptoms
- Overheating, or coolant loss with no visible leak
- White smoke, sweet-smelling
- Bubbles in the coolant, or the system pressurising quickly
- Oil and coolant mixing
- Low compression on one cylinder
- Salt water in a cylinder or in the oil
→ Losing coolant with no visible leak · Milky oil on the dipstick · Marine engine blowing white smoke
Rule out the cheaper causes first
On a marine engine, several faults produce head-gasket symptoms and cost far less:
A perforated heat exchanger tube, pushing seawater into the coolant or coolant overboard through the exhaust. → Heat exchanger service
A perforated oil cooler, mixing oil and coolant.
A corroded aftercooler, putting seawater into the intake. → Aftercooler service
A failed exhaust elbow, letting seawater back into a cylinder. → Exhaust elbow replacement
A failed pressure cap, expelling coolant.
Pressure testing the cooling system and a combustion gas test on the coolant distinguish these from a head problem. Insist on both before anyone removes a head — on a boat, that job is expensive and the access is often poor.
The work
Removal, strip and clean, crack testing, pressure testing, flatness measurement and machining, valve and seat work, new stem seals and guides where worn, and reassembly with correct clearances.
On many marine engines the head bolts are torque-to-yield and must be replaced. So must the gasket.
Corrosion assessment is the marine-specific part. A head that has been run with depleted coolant, or that has had seawater through it, may be corroded in the water jackets beyond economic repair. This is a real outcome and worth establishing before machining money is spent.
Fix the cause
Marine heads fail from overheating or from water ingress, and both have causes that outlive the repair. A new head on an unrepaired cooling system, or behind a corroded exhaust elbow, fails again.
→ Marine head gasket replacement · Marine engine rebuild
What it costs
→ Marine cylinder head repair cost
Find cylinder head repair in your city
Gold Coast · Sydney · Brisbane · Sunshine Coast · Melbourne · Perth · Whitsundays · Cairns · Port Stephens & Newcastle · Adelaide
Frequently asked questions
How do I know it’s the head and not something cheaper? You do not until the cooling system has been pressure tested and the coolant tested for combustion gas. On a boat those tests are essential before pulling a head — a perforated heat exchanger or oil cooler produces the same symptoms for much less money.
Can a corroded marine cylinder head be repaired? Sometimes. Corrosion into the water jackets frequently ends it. Get that assessed before paying for machining.
Do head bolts need replacing? On most modern marine diesels, yes — they are torque-to-yield.
Why did my head fail? Overheating or water ingress, almost always. Both have causes that must be fixed or the repair does not last.