Cooling System Maintenance on Marine Diesel Engines

“Why do I need this service? My engines aren’t overheating or smoking, and they only have 500hrs on them.”

At Scott Marine Power, we often get these types of questions from customers contemplating maintenance on their MAN or Yanmar engines. The Cooling System Maintenancealso known as the 1000Hr or 3200Hr service, provides maintenance on the heat exchanger, intercooler (after cooler/charge air cooler), gear box oil cooler, power steering oil cooler, fuel cooler, sea water cooled exhaust riser and in some cases, the seawater cooled engine oil cooler.  Cooling System Maintenance ensures proper water flow in the engines. Without proper water flow, the engine loses cooling efficiency. If the engine continues to operate inefficiently, overheating will eventually occur, which can lead to significant damage.

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Let us explain, the cooling system gets deposits on both the water jacket and the seawater side of a closed cooling system. A closed system has antifreeze or rust inhibitors on the water jacket side of the engine, while the salt water is used in place of a radiator. 

The antifreeze wears out and the energy release, which occurs millions of times during the running cycle in an engine, acts to remove tiny particulates of iron and aluminum from the engines’ water- jacketed parts. The antifreeze has additives to absorb and suspend these particles, but over time they overwhelm the antifreeze as the additives are depleted. On top of this, water of unknown quality is often added to the coolant, diluting it and adding debris.

The sea water contains microbes, sea grass, clams and barnacles. When an engine runs, these extra minerals are moved through the sea water side of the system. When the engine sits for extended periods, the water deposits fall out of suspension and stick to the metal pieces in the heat exchanger. Over time the deposits clog up the water passages that carry the seawater and don’t allow for a proper heat exchange process.

"Why can’t I just run barnacle buster through my cooling system?" Barnacle Buster has corrosive properties, which can cause damage to gaskets, seals and sensors in the water jacket side! Thus, it’s only suitable for the seawater side. The other reason is that the tube bundle type of heat exchanger systems has an inner (copper/nickel) tube bundle assembly and an outer reservoir.  O-rings are used to prevent the antifreeze and sea water from mixing in the reservoir.
Engine manufacturers, including MAN Marine Engines and Yanmar Marine Engines provide maintenance time interval guidelines so that service is performed before a problem (such as overheating) arises.The manufacturers understand that the marine environment is harsh, so they require these bundles be removed periodically. Ultrasonically cleaned and pressure tested bundles ensure that both seawater and coolant water portions are attended to. Disassembly, reservoir cleaning, and reassembly with new seals and lubricated fasteners are also assured during this routine maintenance. Corrosion occurs whether the engine is running or sitting. That is why the service has recommended time intervals. If this service is deferred, then damage due to corrosion occurs. Preventative work will save a headache and large repair bill!

Have questions? Call 888-584-7668
or email Carmine  

Scott Marine Power
3786 SW 30th Ave
Ft. Lauderdale, FL 33312

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