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Cleaning Engine Parts - In The Real World
By Larry Carley
Regardless of what kind of engine work you do, cleaning the parts is almost always the first step in any job. Parts need to be cleaned before they are machined for a variety of reasons: it helps keep your shop equipment cleaner (which means less mess and cleanup later), it uncovers the bare metal surface so you can see hairline cracks and other flaws that may need to be repaired, and it creates a clean surface that can be painted or left "as is" in the case of aluminum.
Cleaning is also one of the last steps you do after parts have been machined. The first cleaning removed the accumulated dirt, grease, carbon and corrosion from the parts, and the second cleaning is necessary to remove the cutting lubricants, metal chips and/or grinding or honing debris from the parts. The final cleaning is especially important because anything that is not washed away can end up inside the engine. Honing residue that's left in the cylinders will scrub away at the new rings. Metal chips or residual shot blast media that gets trapped in a recess or ends up in an oil galley may find its way to the bearings. These are problems no engine builder wants, so make sure all the parts are as clean as they need to be before the parts leave the shop or the engine is assembled.
Cleaning costs also have to be managed. The labor and expense that goes into cleaning can eat up 10 percent or more of the total cost to rebuild an engine. In some shops, cleaning may account for as much as 20 to 30 percent of the overhead expenses when you factor in time, labor, the cost of the cleaning equipment, cleaning chemicals and disposing of the waste. Cleaning is usually a much higher expense for shops that rebuild older engines with years of accumulated grease and grime than for shops that primarily do performance work on racing engines with mostly new parts.
Regardless of whether you are removing years of accumulated crud or just washing off new or relatively new parts after machining them, every engine builder needs to review the cleaning procedures that are being used in his shop periodically to make sure the procedures are working well and there are no cleaning issues. Maybe you can save some money by making some changes in procedures, equipment or chemicals. Maybe you can reduce the time needed to clean parts by switching to a more effective process. Or, maybe you'd like a process that leaves a better cosmetic appearance on the parts than you are getting now. There's always room for improvement. So there is no excuse to keep cleaning parts the same old way you've always done it if there are better options available.
For example, many shops use a hot tank to clean parts. Various kinds of degreasing solvents, caustics or water-based detergents can be used in these tanks to clean aluminum, cast iron or both. Some do a better job of cleaning cast iron or aluminum than others. So you need to choose a cleaning solution that works best on the kind of parts you clean the most - or add a second hot tank or other cleaning process just for aluminum or cast iron.
Though solvents are very effective cleaning agents and are still used in many areas of the country, they have been banned in some areas because they give off Volatile Organic Compounds (VOCs). VOCs are a major cause of urban air pollution, and many contain compounds that are toxic and have health risks associated with long term exposure. Many solvents are also flammable. But on the plus side, they require minimal maintenance and can be recycled.
By comparison, water-based aqueous cleaning solutions have very low VOC ratings. This makes them a better choice in areas with air quality concerns than solvents. Most water-based detergents and chemicals are also nontoxic, nonhazardous and nonflammable. Water is also recyclable, relatively cheap and much easier to dispose of. Contaminants in the water can be removed chemically, mechanically or biologically (bioremediation), or concentrated by evaporating away most of the water. The only downside is that the concentration of the cleaning solution has to be monitored and maintained for optimum cleaning performance. This means adding make-up water periodically, monitoring the concentration of the cleaning solution, and using a skimmer and/or filter to extend the life of the solution (which can double or triple the life of the cleaning solution).
Cleaning Supply Directory
If speed is essential, a spray washer is often a better cleaning choice than a hot tank because it is faster. A typical wash and rinse cycle in a spray washer may only take 10 to 15 minutes compared to hours of soaking in caustic, solvent or cleaning solution. Automated spray washers clean parts without any manual scrubbing or brushing. Most spray washers use V-jet nozzles and a stationary manifold system to direct water at parts sitting on a turntable inside the cabinet. On some washers, the parts are stationary and the nozzles rotate to vary the spray pattern. Power or pressure washers, by comparison, operate at higher pressures to dislodge dirt and grime and use much larger nozzles. Some washers use a water wheel rather than a pump and nozzles to wash the parts. Either way, the parts come out clean and are ready to machine in most cases.
For water to clean effectively, it usually needs heat. The hotter the better. The recommended temperature range will vary according to the type of equipment and chemicals used, and may range from 105° up to 190° F. Many spray washers operate best in the 140° to 180° F range. If the water temperature is too hot, though, water loss due to evaporation may become a problem requiring more make-up water to maintain the cleaning solution. Some equipment suppliers recommend a slightly lower water temperature when cleaning aluminum while others do not.
Though a relative newcomer to the automotive cleaning world, ultrasonic parts washers will do as good of job cleaning the external surfaces as bead media without damaging ports and other critical surfaces, say experts. Ultrasonic cleaning also offers the convenience of being an automatic process: you can throw the part in, turn it on, and walk away to do something else.
According to manufacturers of ultrasonic systems, many engine builders are using jet spray washers to pre-wash aluminum parts to get the heavy grease off and then using the ultrasonic system to do the precision cleaning.
Ultrasonic cleaning works well because you're not using a high impact force to do the cleaning, so you're not changing the tolerances of the aluminum. It creates a vacuum bubble that when it hits the part and pops it doesn't blow out it implodes. This is what is called cavitation. It is basically sucking dirt off the part you're cleaning.To find out what kind of cleaning processes some of our readers are using, we contacted the following engine builders for their input.
Johnny Bianchi of B&G Machine in Seattle, WA says he has both a hot tank and a spray washer for cleaning big diesel engine blocks and other parts. "We're using a caustic solution (sodium hydroxide) in the hot tank, and a water based cleaning solution in the spray washer. We don't shot blast any engine parts because we don't want any media left inside the engine. We do use glass beads on external parts, and we have considered buying a soda blast machine, but have not yet made that decision."
Bianchi says quality control of their cleaning operations is very important because of the high dollar value of the engines and parts they rebuild. "We do a lot of diesel crankshafts. To make sure the oil galleys in the crankshafts are clean, we do a millipore test. The galleys are flushed with solvent and the solvent is run through an 8 micron filter that traps any contaminants. The filter is then weighed and examined under a microscope to make sure there are no contamination issues."
Bianchi says he has invested over $5,000 in his millipore test stand, but the cost has been well worth it because it eliminates potential warranty problems. "Many of the new MTU diesel engines are running half the bearing clearances of a typical Caterpillar engine, so cleanliness is especially important on these applications."
As for waste disposal, Bianchi says all the drains in the shop have been plugged because they are not needed. "We skim the oil off our waste water, then transfer the water to a holding tank where it is neutralized and evaporated. The slurry that is left can pass a cold plug test and goes out with the regular trash. We received an environmental award called a Green Works Certificate from the City of Seattle for our waste reduction efforts."
Randy Bauer at Jasper Engine & Transmission in Jasper, IN says his company uses a molten salt bath cleaning system that runs at 735° F. The salt bath is used primarily to clean cast iron parts, but can also be turned down to 625° F to clean certain aluminum parts.
"After the parts come out of the molten salt, they are rinsed, dipped in an acid tank to remove surface rust, then rinsed again in an alkaline tank to neutralize the acid. If any additional cleaning is needed, the parts may then be shot blasted."
Bauer said aluminum parts are usually cleaned and degreased in a hot tank with agitation that loosens the dirt and grime. If parts have blind holes, recesses and other hard to reach areas, they go into an ultrasonic tank, which he says works much better than soaking and agitation alone to clean the parts. Aluminum parts are then finished by blasting with plastic media. "Plastic media doesn't distort or damage the metal, and it does a great job removing dirt and carbon. But it does not remove stain." But Bauer said that doesn't really matter because Jasper always paints their engines after they are assembled. The aluminum parts are sprayed the same color as the other parts on the engine (typically gray or black).
TEM MACHINE SHOP
In some areas, such as southern California, waste disposal is such an expense that shops need to use cleaning processes that keep waste generation to an absolute minimum. Rich Oliver of TEM Machine Shop in Napa, CA says having a drum of solid waste insured and hauled away by a licensed hazardous waste disposal firm costs as much as $1,400.
Consequently, he has a standard minimum cleaning charge of $20 on all jobs ($75 if the parts are really dirty or greasy). What if a customer doesn't want his parts cleaned? Then he is charged $20 to cover the cost of cleaning the shop equipment that is used to machine those parts. Either way, the customer helps pay for the shop's cleaning and waste disposal expenses.
Oliver says he cleans aluminum parts in a jet washer with a citrus-based aqueous cleaning solution, then oven dries the parts at 180° F before blasting them with glass beads or soda. Drying the parts helps keep the blast media from sticking to the metal. The soda leaves a nice, natural-looking finish that doesn't have to be painted.
George Anderson at Gessford Engine in Hastings, NE (2004 Machine Shop of the Year winner) said he relies on a traditional hot tank to clean diesel engines. He says his shop does not clean many aluminum parts, so a hot tank is all he needs for cleaning large cast iron parts. For cleaning pistons and other small parts, he uses a solvent sink.
"Most of the cleaning we do is the initial degreasing and removing dirt. We seldom do a final cleaning unless we are also assembling the engine, which we usually don't do."
Anderson said he has a detailed price sheet for cleaning everything from small 4-cylinder passenger car engines up to the largest diesel engines. The charge depends on the engine and how difficult it is to clean based on previous experience. For example, Anderson charges $76 to clean an average smallblock Chevy V8 and $179 to clean a Caterpillar 3406 diesel.
Dick Bowshier of Dick's Performance in Urbana, OH is rather unique in that he doesn't do much of his own cleaning. "I have an outside source who cleans my cylinder heads and blocks. I send them dirty parts that need to be cleaned, and they send me head work in exchange. It's a win-win arrangement for both of us. They have a flame rotisserie and shot blast system that does a great job on cast iron parts. Aluminum can't take the heat, so if I have aluminum parts that need cleaning, I have a high pressure spray washer or use solvent or carburetor cleaner. Carburetor cleaner works great for removing carbon from valves."
Bowshier said he charges customers a flat $20 fee for cleaning a pair of cylinder heads, and $35 to clean an engine block. He usually doesn't paint aluminum heads because most customers just want the bare metal finish. But he does often spray aluminum intake manifolds, water pumps, timing covers and valve covers with clear paint. The clear coat helps preserve the bright finish and keeps oil and grease from soaking into the metal.
RAM RACING HEADS
Rich Maitre of RAM Racing Heads in Oxford, PA said most of the engines he works on are performance engines so cleaning is not a big issue. The parts are relatively new and not caked with years of grease and dirt, so a light degreasing or washing is often all that's necessary. Maitre said he uses a spray washer, then blasts the parts with glass beads where necessary to clean up the parts. A final wash is given in the spray washer before they are machined, then a final wash when all the work is done.
"We charge a flat $70 fee to disassemble, degrease and clean a customer's engine. On OEM style valves, we just blast clean them. On titanium or stainless steel performance valves, we put them in a drill chuck and use a Scotch Brite pad to clean them up."
The most difficult engines to clean, Maitre says, are often marine engines because the water jackets are often caked with deposits. On these, he may use silicon carbide or aluminum oxide media to blast off the deposits. Cylinder heads on dirt track cars can also become caked with baked on mud, which may require blasting with aluminum oxide to get clean.
Another cleaning challenge is aluminum heads that have been painted. Maitre said it is too time-consuming to blast off all of the old paint, so he uses a strong solvent that is similar to carburetor cleaner to eat off the paint. "Some of our customers just want a bare metal finish on aluminum heads. But a lot of street racers like to paint the heads the same color as the block to conceal the fact that they are running aftermarket performance heads on their engines. We just give them what they want."
And so it goes with most cleaning processes. You find a process that works well for you, is cost-effective and satisfies your customer's needs.
REDUCING CLEANING & WASTE DISPOSAL COSTS
One of the "hidden" costs of cleaning engine parts is disposing of the used chemicals and other wastes that are generated by the cleaning process. With thermal cleaning systems, most of the volatile organic compounds are burned up, leaving only residual ash inside the oven. With wet cleaning systems, however, sludge and oils inside the tank or spray wash cabinet have to be filtered, skimmed or removed creating potential disposal issues.
According to RCRA regulations, a substance is classified as waste when it is no longer a usable product. A barrel of caustic or a drum of degreasing solvent is not a waste as long as it is still being used to clean parts (or is being stored for future use or reuse). But once a cleaning product becomes contaminated with sludge and is removed from the cleaning equipment, it becomes "waste" and may be subject to hazardous waste storage and disposal regulations if it contains any ingredients that make it hazardous.
The EPA publishes a lengthy list of chemicals that are considered hazardous. Generally speaking, a material must be labeled hazardous if it contains more than the allowable amount of:
Corrosives such as strong acids (phosphoric, hydrochloric, etc.) or caustics (sodium hydroxide) that have not been neutralized. This would be determined by measuring the pH of the liquid.
Toxic or poisonous chemicals (most petroleum distillates & solvents).
Organic solvents or chlorinated hydrocarbons (such as methylene chloride or carbon tetrachloride).
Explosive or flammable chemicals with a flash point of less than 140° F). This would include most solvents, benzene, aromatic hydrocarbons, mineral spirits, toulene, naptha, ketone, alcohols, paint thinner, etc.
Heavy metals (lead, mercury or cadmium). This would include contaminated shot blast, oven ash, cleaning solutions and sludge.
Cyanide from electroplating or metal treating operations.
Any other substance that the EPA, Department of Transportation or state regulatory agencies have labeled hazardous or toxic.
Any machine shop that generates more than 220 lbs. of hazardous waste per month is considered a "Small Quantity Generator" (SQG). The 220 lb. figure includes all solid and liquid hazardous waste generated by all aspects of your business, including any additional facilities (such as an installation service or warehouse that you might also operate). If you are a SQG, then you must comply with all the various federal, state and local laws regulating on-site storage, transport, disposal and/or treatment of hazardous waste.
To reduce waste disposal issues, those who are currently using caustic solutions in a hot tank can switch to non-toxic detergents, and use an evaporator to reduce the volume of the waste water as much as possible before disposing of the slurry. An evaporator can reduce 1,000 gallons of spent cleaning solution down to 50 gallons of sludge.
Another option is to switch to thermal cleaning using either a convection oven or a direct-flame rotisserie oven to clean parts. An oven requires no chemicals and uses no water. The ash that's generated is a much smaller volume than the waste typically generated by wet cleaning, and all of the grease and oil is burned as it goes up the stack. Convection ovens typically operate at 700° F when cleaning cast iron, or 450° to 550° F with aluminum. Direct flame rotisserie ovens, by comparison expose the surface of the parts to temperatures of up to 1,100° F, which is hot enough to burn off even synthetic oils. Afterburners that operate at temperatures of 1,400° to 2,200° F assure low stack emissions.
Abrasive cleaning is yet another option, which can be used by itself or in combination with wet or thermal cleaning systems. Manufacturers of shot and bead blasting equipment, tumblers and dry vibratory cleaning equipment say their approach is the most environmentally friendly of all because it doesn't use any chemicals, detergents or water, and generates no VOC emissions or chimney emissions. The dust and cleaning media residue that's generated by abrasive cleaning can be separated and collected by filtration, which reduces and condenses any potentially hazardous material that must be disposed of.