SLUDGE FORMATION IN CRANKCASE OIL.

Southland Times, Issue 20669, 15 December 1928, Page 16 (Supplement)

SLUDGE FORMATION IN CRANKCASE OIL.

Motor truck operators arc sometimes surprised and perplexed to find the oil in the crankcase of their engine has turned to a thickened, slimy—and in some cases, an almost pasty—mass, which is practically impossible to distribute through the lubrication system. While- this condition of “sludging” is I known to some operators, its cause and remedies are practically mysteries to the great majority. Causes of Sludge Formation. The formation of "sludge” in crankcase oil is due to a combination of several causes, and it is really an emulsion formed by water in the presence of road dirt, carbon dust, and minute metal particles, such as are always present in an engine crankcase. This conxiition is possible even with very high quality oils which, in their fresh and uncontaminated state, do not easily combine with water. Water in the Crankcase. The presence of water in the crankcase is often mystifying, and the reason for its accumulation in the oil pan is not generally understood. In exceptional cases—which should be immediately remedied—the source of the greater part of this water may possibly be an improperly fitted head gasket or even a cracked cylinder. Omitting from consideration these exceptional cases, it is practically impossible to prevent the presence of water in the crankcase of a motor vehicle. In fact, in our laboratory work, we have noted the presence of water in a crankcase which was previously cleaned, dried and warmed, after but three minutes of operation. Water vapour suspended in the air settling on the cooler metal parts in the crankcase causes condensation of the moisture. One of the most common- sources of water vapour in the motor comes from the exhaust gases of combustion, and its presence may be demonstrated by placing an ordinary glass tumbler over the end of the muffler pipe and notice the rapid accumulation of water drops condensed from the exhaust. The water (hydrogen and oxygen) is chemically formed in the combustion chamber by the explosion- of the motor spirit (hydrogen and carbon) in the presence of the oxygen in the air which is part of the combustible mixture. Contributory Causes. With some engines this water accumulation is much greater than in others. Worn engines naturally allow a greater proportion of exhaust gases to reach the crankcase than those which are in- good mechanical condition. Also a not running motor permits much less water collection in the oil pan than a cold one. Engines used in short runs, with frequent stops or much idling, may be expected to be more subject to this annoying condition than those in which the crankcase becomes heated sufficiently so that the greater part of the escaped ex haust gases are thoroughly warmed and pass on out through the breather. If the oil is fresh and of high quality the water will not remain in permanent suspension: but as the oil becomes contaminated with the minute particles from metallic wear—road dirt, free carbon from the underside of the piston heads—moisture resulting from the combustion of motor fuels —its ability to separate from the water is lessened. Laboratory tests show very surprising figures with different oils as to demulsibility—or their ability to separate from water —in the presence of contamination, verifying the statement that the readiness i of fresh unused oil to separate from clean water cannot be accepted as the sole measure of its suitability for use in any particular engine. Fortunately, it takes quite a little time for the water and contamination to form the oil into a dangerous “sludge” under the whipping action of the crankshaft and connecting rods and the heat of the engine operation. Most generally the dilution of the crankcase oil by unburned portions of the fuel is sufficient to thin the mixture and delay sludging. Sludge formation must be carefully watched, otherwise, the complaint will become chronic. Unless :he crankcase is perfectly cleaned after sludge has once formed, the trouble will appear again with startling rapidity. Particles of the sludge remaining seem to act as catalyzing agents to hasten the emulsification of the fresh oil. The Remedy. The remedy is tc use a high quality oil of the correct grade and character and maiiK tain this oil in good condition. The good mechanical condition of the engine is, of course,important. Satisfactory performance of any unit is dependent on its mechanical condition. Periodic crankcase draining is absolutely essential. Inasmuch as colder operating temepraturee are encountered in winter service, there is a greater tendency toward crankcase oil dilution and contamination than in summer driving, and the oil should be changed more frequently. Drain the oil after a run while the engine and crankcase are warm. The oil is much more fluid when heated, and will more readily carry off the accumulated sediment, thereby obviating all excuse for the dangerous practice, all too common, of using kerosene for flushing the crankcase. When kerosene is used for this purpose, some of it is bound to be trapped in various pockets and partitions of the crankcase, remaining to dilute the new lubricating oil when added. If it is desired to flush the crankcase, use a quart of two of fresh engine oil, allowing the engine to turn over slowly for a few minutes. Then drain and fill with the proper quantity of fresh oil. At least twice each year—more often is desirable—the oil pan should be completely dropped, and the pan, as well as the entire lubricating system, thoroughly cleaned with kerosene and motor spirit. Use clean cloths —avoid cotton waste or linty rags. Carefully remove all cleaning solution before replacing pan and filling with fresh oil. The following suggestions will be found of assistance in avoiding oil sludging: How to avoid Oil Sludging. First: ——While the motor is warm drain ■ off a cupful of oil. If it contains a quantity of water, make it a practice to repeat this operation every three or four days, and by so doing, remove the cause of much worry. Second:—Drain the crankcase oil .periodically. Every 500 miles in winter and every 750 miles in summer operation. Clean the oil screen at these times. Draining weekly in winter and semi-monthly in summer may be found more convenient. False economy occasionally prompts operators to unduly extend the draining periods. Statistics show Correct Lubrication to be one of the smallest items of operating cost and the greatest insurance against wear, depreciation, and expensive loss of truck service through shut-down. Third:—The selection of fuel has ag reat deal to do with water accumulation. Highly volatile motor spirit generally gives better satisfaction. If you are using a volatile motor spirit, it is advisable to continue its use rather than replenish your supply at random. Fourth:—lf sludging should occur, make positive that the last trace of the formation is cleaned from the crankcase before refilling. Do not rely on flushing—drop the oil pan and clean it thoroughly. Published by—Engineering Division, Automotive Dept., Vacuum Oil Co.. Pty ’ Ltd.