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Home , Antifreeze, Cooling, Heat exchanger

BOATKEEPER

Coolants and System Maintenance From Pacific Fishing, February 2001 By Terry Johnson, University of Alaska Sea Grant, Marine Advisory Program 4014 Lake Street, Suite 201B, Homer, AK 99603, (907) 235-5643, email: [email protected]

Marine diesel specialists say the most A 50-50 mix will stay fluid down to succinctly: “The importance of a properly frequent source of premature engine failure minus 34°F and will prevent freeze dam- inhibited cannot be overstressed.” is the cooling system. Improper age to a somewhat lower temperature. Ves- An intricate maze of , steel, and inadequate cooling system maintenance sels that winter at temperatures colder than bronze, , and sometimes aluminum can result not only in catastrophic overheat- 40 below may go as high as 60-40, while passages comprise a marine diesel cooling ing, but also in damage and even those that operate in warm may go system, an ideal breeding place for galvanic vessel flooding. Because most of the cool- as low as 30-70. Straight should corrosion, particularly if seawater is ing system is internal to the engine and diffi- never be used as a coolant because it doesn’t present. (Some with keel coolers cult to observe, damage can occur gradually transfer as well as a mixture, nor does for the still incorporate raw over time, essentially rotting the core of an it protect against freezing as well. Minor over- for exhaust elbows and other periph- otherwise hearty diesel. heating sometimes can be remedied by di- eral cooling.) Zinc plugs should protect the Nearly all marine diesels are cooled by luting the coolant with more water, or by raw-water side, but are not normally fitted either a keel cooler (or some variant such switching to an antifreeze with different in the freshwater system. Furthermore, vi- as grid cooler or skin cooler), or by a heat properties. According to a re- bration inside the block, particularly around exchanger. Both systems depend on circu- cent posting on an Internet diesel message wet liners, causes tiny pockets of lating coolant to remove heat from the en- board, adding the proper mix of Nalcool reduced , where heated coolant gine block and transfer it to the 3000 will lower the engine operating tem- vaporizes, forming bubbles of . As environment. Closed systems are called perature 7-10 degrees, which can be impor- these bubbles collapse against internal sur- “freshwater cooling” because seawater is not tant in a high-output engine. faces they physically erode the metal. This circulated through the block, but straight Select carefully the water to be used in “ erosion” can eat pinholes right fresh water should not be used in diesel coolant, since the and chlorine in through liners and cooling jacket walls, al- engines. Coolants normally consist of a mix city water enhance corrosion, and mineral lowing coolant into the cylinder. of water, antifreeze, and a conditioner or impurities contribute to scale buildup. Chlo- Scale, a hard coating of mineral solids inhibitor. rine is particularly corrosive to aluminum, derived from magnesium, calcium carbon- which is used in blocks, heads, and heat ate, and other impurities in the water, may Coolant must: exchangers of some lightweight, high-speed clog passages and diminish the transfer of • effectively remove heat diesels. Well water should never be used in heat through the water jacket walls into the • prevent freezing and resultant block cooling systems due to mineral content. You coolant. A quarter inch of scale on top of damage can get your water lab tested for impuri- one inch of cast iron slows heat transfer to • prevent deposits of scale and sludge ties, and in a pinch you can use a water- the same rate as four inches of cast iron on interior passages softening additive. Some antifreeze brands alone, enough to cause overheating. Sus- • inhibit corrosion are blended to compensate for impurities pended solids also grind away seals, caus- • prevent cavitation erosion in city water. Most municipal water is sat- ing water pumps to . • lubricate components such as water isfactory for cooling systems, but “de-ion- Popular supplement additives include pumps ized” or distilled water is best. Baldwin’s BTE, Penray’s Pencool (for- • be compatible with hoses and seals merly known as Nalcool), and DCA by Use a Conditioner Fleetguard. Sold as either or pack- Most operators know that a 50-50 mix- However, you can’t rely on pure water and ages of water-soluble powder, they are ture of antifreeze and wa- antifreeze alone to protect your cooling sys- mixed into the water-antifreeze coolant. ter provides good heat transfer and freeze tem. Any high quality, heavy-duty, low-sili- Some brands of antifreeze (Caterpillar and protection. (It’s usually yellow or green. cate antifreeze is appropriate for marine Fleetguard among them) are formulated The pink stuff, sometimes called “RV anti- diesel use, but most need a coolant condi- with conditioners included. freeze,” is , and is non- tioner, also known as inhibitor or supple- Conditioners become depleted with use, toxic for winterizing drinking water mental coolant additive, formulated to and coolant should be tested twice a year. systems. It transfers heat poorly and should protect surfaces from both galvanic corro- Some makers sell test strip kits that allow not be used as a coolant. Unfortunately, the sion and cavitation erosion, and also pre- you to check your coolant for conditioner color doesn’t always indicate the contents, vent or reduce the accretion of scale. The strength, and also may indicate presence of so read the label.) Detroit Diesel 71-series manual states it combustion gasses, electrical current, etc. Going a step further, you can send coolant samples to a test lab (testing kits are sold for this purpose) which will return an analysis indicating total dissolved solids, pH (acid- ity), glycol percentage, and the freeze point. Be sure to use only the test strip made for the coolant you are using, and don’t mix ad- ditives from different makers, or add a condi- tioner formulated for one antifreeze to a dif- ferent antifreeze. They may not be compat- ible because different manufacturers use dif- ferent bases. If changing brands, drain the sy- stem and flush before adding fresh coolant. Because solids usually are present in coolant, some mechanics say a coolant fil- ter is a good idea, even essential, while oth- ers say it’s unnecessary. Follow your engine manufacturer’s recommendation. If you do decide to use a filter, select carefully—some have surface filtering elements in the 15-60 If you have a , once every Coolant can also escape through faulty micron size range, others have deep filters couple hundred hours check the zinc plugs. seals elsewhere in the cooling system, in- at 1-5 microns. Obviously the latter take more Bang them with a hard object or scrub with cluding the water seal rings crud out of your coolant but also need more a wire brush and most of the corrosion should or the head , and through in oil frequent replacement. Some companies, flake off, exposing nearly bright metal. If not, coolers, coolers, gear oil coolers, cabin Baldwin and Gulf Coast Filter included, or if they are more than 50 percent dimin- heaters and other devices that are plumbed make filter devices that incorporate a con- ished in size, replace them. At around 500 to coolant lines. Don’t use any antifreeze trolled-release coolant conditioner. The fil- hours, drain the raw water side and clean containing methyl , which can dis- ter should be changed in accordance with with a wire brush. At the time of engine over- solve seals and hoses, and don’t put any manufacturer recommendations. haul or if there is a coolant problem, disas- soluble oil or any kind of sealer in Antifreeze doesn’t deteriorate or lose its semble the heat exchanger, removing the your cooling system. (Oil mixed with eth- ability to prevent freeze damage very quickly. core, and inspect the tubes. Minor deposits ylene glycol forms a varnish that can cause Some sources say that as long as it is rea- can be pushed out with a rod of soft mate- engine failure.) Coolant can also leak sonably clean and the conditioner potency rial, such as a wooden dowel, or a rifle-clean- through a faulty pressure cap or pinhole is maintained, it is good for several years. ing rod and brush with oxalic acid solution leaks due to corrosion in castings such as Follow your engine manufacturer’s recom- can be used. Don’t use a hard rod that could the heat exchanger or . You mendation; for example the recommended damage the thin tubes. If rodding can use a pressure tester to detect breaches change time for Caterpillar’s ELC is three doesn’t clear the deposits, take the core to a of system integrity. years or 3,000 hours, and with addition of radiator shop for cleaning in a chemical bath. Remember, if one gasket has started to an extender is good for six years or 6,000 Periodically, and any time coolant level leak, it’s time to replace all such , hours. Otherwise, it’s a good idea to test in the expansion tank drops, check the because the others will soon start to leak also. the conditioner annually or each 500 hours. “weep hole” at the bottom of the freshwa- Inspect hoses and hose clamps at least A word on draining antifreeze: the stuff ter circulating pump. If it is weeping, or even once a year. Cracked, soft, or puffy hoses is poisonous and classified a hazardous if it shows stains where it has been weeping, should be replaced, as should any hose material, so dispose only in approved re- it may be an indication that the water pump clamps that exhibit rust or cracks. ceptacles, never on the ground or in open seal is going. Replace it right away, or you’ll If your system includes a raw water containers. Antifreeze tastes sweet to ani- soon find you can’t keep coolant in the sys- pump, drain it when winterizing by loosen- mals, particularly dogs, but the result of tem, and this leads to overheating and en- ing the end plate screws and pulling the end lapping it is a slow and agonizing death. gine failure. (That is, unless the pump has plate out a bit, or better yet, remove the a type seal, which is designed to leak impeller so that it doesn’t take a set. (If the System Maintenance a little to provide cooling and lubrication.) boat is in the water, be sure the seacock is Even with correct coolant, cooling systems Some types of engine water temperature closed, and tag it so you will remember to require some maintenance. When the anti- sensors don’t show an overheat condition replace the cover and reopen the seacock freeze is drained, the system should be if the water level drops below the level of before starting the engine.) Also, check the flushed with a radiator-cleaning compound the sensor. This means that if your system sea strainer for clogging, and be sure to or a de-solvent consisting of one part muri- develops a leak, such as through the circu- drain it thoroughly when winterizing, or the atic acid to two parts water. Afterward, re- lating pump seal, the coolant could escape, water inside may freeze and break the con- verse-flush the system using air pressure to the engine could fry, and the alarm wouldn’t tainer. blow hot water through the in the sound. Consider installing a coolant level The daily pre-starting ritual includes opposite direction of its normal flow. alarm in your expansion tank. checking the fluids, which means both the oil and the coolant levels. And merely look- ing at the little recovery tank doesn’t 7. Did the overheating condition appear do it; open the expansion tank and look in- after replacing the coolant? The side. problem could be an air lock in the system. This is particularly likely Troubleshooting where there are long hose runs, such The possible causes of overheating are as to water heaters and cabin heaters. numerous, but you can start with a brief Bleed the system by starting at the checklist: water source and progressively open- 1. Is it really overheating? Gauges of- ing fittings until any air is vented and ten fail or provide faulty readings. water comes out. Check with a separate thermometer. 8. Did overheating occur after chang- 2. Is there coolant in the system? Open ing coolant? The problem may lie in the cap and check the tank. If not, different heat transfer properties in you have a leak, so start looking for the new coolant mix. You may need it. Meanwhile, you can use plain fresh to dilute with water or revert to your water as a temporary coolant. Allow previous brand of coolant. the engine to cool, then add the water slowly so that it doesn’t cool any cast- 9. If overheating developed after modi- ings so quickly that they crack. fying the hull, changing prop, add- ing weight, increasing injector size, 3. If coolant is vanishing, check the or adding power takeoffs to the en- header (expansion) tank cap (if it is gine, the problem could be an over- loose or defective coolant may escape loaded engine. Does it reach its rated there), the weep hole in the circulat- wide open speed? Black ing pump, and all the system fittings. smoke indicates rich fuel setting, If you find coolant in your engine which raises temperature. The solu- oil or gear oil, or if you have white, tion lies in engine adjustments or re- steamy exhaust the problem is likely engineering the system. ✦ a corroded oil cooler, , or other internal seal.

4. Is the coolant circulating? You can watch it swirling in the header tank (once the engine has warmed and the has opened). If not, the circulating pump has malfunctioned, or the passages are clogged.

5. Is the thermostat operating correctly? On most engines they are easy to remove and inspect. You can test by putting it in a pan of water with a ther- mometer and heating the water until the thermostat opens,which should begin at between 165 and 180 degrees and complete 15 degrees hotter, de- pending on model. New engines have 190 and 205 degree . Thermostats are cheap—carry spares.

6. If you have a heat exchanger, is the raw water system working properly? Look for flow from the wet exhaust, and check the seawater strainer. Mud or kelp can plug the intake grate. Blocked flow, stripped raw water pump impeller vanes, or loose v-belts could be the problem.