You don't know what quiet means until your diesel goes "clunk" and dies—silence may be golden, but it rarely bodes well. "Clunk" is what a snapping crankshaft sounds like, for example. I once lost a crank halfway across the Gulf Stream, leaving me adrift on a moonless, star-filled night. Mea culpa: If I had included oil analysis in my regular maintenance program, it probably would have warned me that things weren't copacetic in my diesel.
Analysis of lubricating oil is a dirt-cheap service that can pay you back many, many times over by revealing incipient problems before they become disasters. Most labs charge less than $25 for a standard oil analysis, which includes a spectroscopic examination of the oil to determine the levels of metals, additives, and possibly coolant. Other tests measure viscosity and the percentage of solids in the oil. The test report will include possible causes of any irregularities. Your mechanic can determine the best course of action or if further, more specific, testing is needed. (Elemental analysis, for example, discovers very small particles of metal in the oil, smaller than those detected by standard tests.) And it's not just for diesel engines: Analyzing oil from gasoline engines and marine gears is smart, too. Either way, it's not only cheap, but easy. Here's what you need to know to analyze your oil.
First, find a lab; most will provide all the equipment and supplies you need to draw and submit the sample. POLARIS Laboratories and Blackstone Laboratories are good ones, but an Internet search may turn up one in your neighborhood. SeaKits sells a variety of fluid-analysis kits packed in waterproof boxes; prices include prepaid mailers for sending your samples to Polaris. A kit with a vacuum pump, tubing for drawing the samples, three collection bottles, and three prepaid analyses costs $95.
Always analyze oil that's been circulated through the engine enough to pick up impurities and contaminants. The only time most people analyze oil is when they're buying a used boat—surveyors recommend it—but often brokerage boats have been laid up with fresh oil in the crankcase. Analyzing fresh oil won't tell you much. Instead, draw a sample from oil with 30 or 40 hours on it, at least, or take one when you change the oil. You need only a few ounces. Run the engine until the oil is hot before sampling.
An oil-change system makes sampling easy, but take the sample when about half the old oil is pumped out. You don't want to sample from the first oil that comes from the bottom of the sump, where lots of gunk collects. You can use the dipstick pipe, too—a better method if you're sampling between changes. Withdraw oil using a pump attached to tubing pushed down the pipe. Labs sell inexpensive (about $25) vacuum pumps specifically for this purpose. Measure the dipstick, and insert the same length of tubing so you don't sample the dregs of the sump. Discard the tubing afterwards—reusing it could contaminate later samples with remnants of earlier ones. Fill out the analysis form, and send the sample jar to the lab. In a few days you'll get the results (usually via fax or e-mail) with any potential problems highlighted. Discuss actions and remedies with your mechanic.
At $25 a pop, you can't afford not to sample your oil regularly. If it saves you one "clunk" over your entire boating life, you're ahead of the game.
Ask the Experts: Elizabeth Nelson
The question: Many laboratories offer coolant testing along with oil analysis. why should I have my coolant analyzed?
The answer: Few people know as much about coolant testing as Elizabeth Nelson, coolant program manager at POLARIS Laboratories. Nelson has more than 30 years' experience in researching, analyzing, and testing coolants. She has written five technical publications and trained countless mechanics, technicians, manufacturers, and others working in the field.
"Oil is the blood for an engine; coolant is its lymph system," Nelson says. "Forty to 50 percent of premature engine failures are due to problems in the cooling system." Coolant analysis can spot trouble before it can cause permanent damage. The lab report will highlight problems and abnormalities and suggest remedies. Catch a mechanical problem early enough, correct it, and you may not need to replace the coolant, she says.
Nelson recommends Level III testing twice a year for yachts—once in the spring before the season starts and again before layup. Level III testing checks for chloride (salt) as well as nitrates and sulfates; it costs less than $100 at POLARIS. It takes just three ounces of coolant, extracted with a clean vacuum pump. Between analyses, use test strips to check the pH, nitrite, molybdenum, and glycol levels (if glycol is the coolant) at every oil change; acidity or inhibitor depletion is a sign of contamination.
It doesn't take a major catastrophe to cause problems. Low coolant pressure, blockages, or even mechanical conditionss—coolant lines run too close to a turbocharger, for examples—can create higher running temperatures and/or hot spots. Internal boiling reduces nitrite and lowers pH. Acids then form that can lead to severe metal corrosion.
Electrical grounding issues can affect nitrite, too. "Stray currents take the path of least resistance," Nelson says. "Typically that's through the cooling system. The stray current destroys the nitrite and causes severe liner pitting. This destroys an engine faster than anything else."
Other contaminants often arrive via the faucet: Chlorides and sulfates can form acids and scale. Acids attack soft metals; scale formation causes heat-transfer loss. Both can come from the water that's mixed with the glycol or other coolant. "Bad water can destroy a good coolant, rendering it useless," Nelson explains. "It's important to know the contaminant levels of the water you put into the system." Salt can get into the system through air leaks, too, or by seawater contamination. Coolant analysis will discover the chloride and determine where it's from: Sea salt has more magnesium, while airborne salt has more calcium.
All of the above is made worse if the engine runs normally at a high temperature, like many of today's high-output, low-emissions diesels. And, Nelson adds, the increase is exponential: "A 160-degree operating temperature should be your baseline. For every 15 degrees above that, the potential for metal pitting and scale formation doubles."
This article originally appeared in the May 2008 issue of Power & Motoryacht magazine.