Cleaning & Repair
Possible solutions discussed here in the order of my best guess of preference.
1) Hot soapy water (and/or boiling in tub)
2) Simple Green
3) Paint thinner
5) Castrol "Multi-purpose"
7) Schaeffer's citrol
5) Castrol "Purple Power"
8) Amsoil "Power Foam"
I have three cases I just finished cleaning. I did a modest scrub with gas and dish detergent like Dawn, then rinsed them with the garden hose. Next, I took them down to the car wash and lightly scrubbed with dish soap again; blew them again with the high pressure washer and detergent. After a quick wipe down and letting them dry for a day they where ready for work.
I made inquiries about the best way to desolve grease at a couple car garages. The most experienced advice seemed to think the closest thing legal to Stoddard Solvent was paint thinner. I went to a auto rebuild shop and ask them what they used; they said they fill their engine tank with "Simple Green". They first hit hard spots with a can of Amsoil "Power Foam" on warm engines and reported it worked much better than just soaking in Simple Green.
Castrol works pretty good but Schaeffer's Citrol is considered better. Castrol doesn't contain any acid. It's KOH, potassium hydroxide. Pretty strong and can etch aluminum (and magnesium). Only use Castrol Purple or Fantastik for quick dips and only if the part can be completely washed and dried in detergent water; or it will etch the part and ruin it.
I did leave some parts soaking in Simple Green in cleaning bucket outside through one winter. The next spring aluminum parts were unharmed but the magnesium had 3 or 4 deep etched areas about the size of a penny and 1/8 inch deep. The Simple Green did have quite a bit of water in it so to this day I do not know if the water played a part or not.
Cleaning VW Engines
Heat accelerates chemical processes. Cleaning parts is largely a chemical process. Always use the hottest temperatures practical. (A few charcoal briquettes and a 'hobo' stove will keep a pot of TSP solution simmering for hours.) If you are unable to heat your cleaning solution, or when it is unwise to do so, you must schedule additional soaking time to give the process a chance to work. Cleaning parts calls for a surprising variety of brushes and scrubbers. I use a variety of rifle, pistol and machine-gun bore-brushes in both bronze and fiber. Cutting the bristles of a regular paint brush to about 1" will provide enough stiffness for scrubbing.
Do not use steel wool on aluminum or magnesium parts. Microscopic fragments of steel become embedded in the softer metal and cause electrolytic corrosion. The dismantling, cleaning and inspection of a used engine takes considerably more time and consumes far more materials than most realize. In a majority of cases this labor and expense will be wasted, for after going through this lengthy, messy and exacting procedure you
Cleaning Steel Parts
Steel parts are cleaned using either lye (sodium hydroxide) or trisodium phosphate. The traditional 'hot tank' formula was a solution containing lye. Be advised that lye will dissolve both aluminum and magnesium. Lye is available from grocery and hardware stores. Oven cleaners usually contain some amount of lye, as do most drain cleaners. Lye is a powerful caustic. Don't just read the instructions, follow them. Gloves and suitable eye protection should be worn when working with lye.
Trisodium phosphate is usually found in the paint department of hardware stores. Some soaps used in dishwashing machines contain trisodium phosphate. Many janitorial supplies contain either lye, trisodium phosphate or acids, from hydrochloric to phosphoric. Read the labels. Many communities have banned the sale of certain chemicals in the mistaken belief that doing so will protect the environment. Yet those same chemicals remain available in janitorial supplies and household cleaning agents.
I clean most steel parts by boiling them in a solution of trisodium phosphate, discarding the solution onto my compost heap. Remove any rust by carding (ie, using a scratch wheel) or with phosphoric acid, which is available in the paint department of most hardware stores. A saturated solution of acidic brine is also an effective derusting agent. Once steel has been degreased and derusted it must be protected by either plating, painting, waxing or oiling. Since an aircraft engine spends it's life exposed to the elements cadmium plating is the best protection but paint, if properly applied, will also serve.
Cleaning Nonferrous Parts
Methyl Chloride, the active stuff in paint remover, is the classic 'cold tank' solution, usually mixed with kerosene or diesel fuel. For most of us the most common source of methyl chloride will be in the form of carb cleaner. A five gallon pail of the stuff will accept your heads (once dismantled) one at a time. It may also be used on your crankcase but the problem here is finding a suitable container. Methyl chloride will dissolve even baked-on deposits in the combustion chamber, which should give you some idea as to why you don't want to get it on your skin. After soaking a part in carb cleaner it is rinsed in solvent then blown dry. The 'solvent' I'll mention frequently is common white mineral spirits paint thinner, to most of us. Do not use gasoline. Tthe modern-day stuff sold under that name contains carcinogens that can be absorbed through the skin. Kerosene, diesel fuel and even JP5 may be pressed into service.
To properly clean a used crankcase you must have access to all of the internal passageways. Begin by removing the oil pressure control valve and the volume control valve (if so fitted). You'll probably need to fabricate a special screwdriver for this task. Be very careful to save the aluminum washer(s). These are difficult to find and you may have to reuse them. Put the parts cap-screw, washer, spring & piston in that Special Place where you stored the main bearing dowel pins. It is standard aircraft practice to modify the oil control/pressure valve cap screws by welding on a small steel tang that will allow the cap screw to be secured with safety wire. As with all other hardware, the cap screws must be plated or painted.
In a properly built engine the piston-type oil pressure & control valves are normally replaced by ball-type valves after installing a suitable valve seat. Due to the pulsations of the pump, piston-types tend to wear the bore rather rapidly and once worn, may cock far enough to become wedged. This can cause all of the oil to be by- passed to the sump. Robbed of oil pressure, a catastrophic failure is only minutes away. Ball-type valves, which are the standard in the industry for this purpose, have none of those faults, plus they provide a wider range of control than does the piston type. (When working with Volkswagen engines it is important to always keep in mind that you are dealing with 1930's automotive engineering technology.
By modern standards, the Volkswagen engine has a host of potentially lethal faults.) If you do not plan to modify your oil control/volume valve(s) to ball types, be especially careful when cleaning the bores. Do NOT use any form of abrasive nor a metal brush on the bores of the valves, which must form a perfect fit to their pistons. The myth of the Volkswagen's reliability, largely created by the Doyle-Dane-Bernbach ad agency, is perpetuated by a host of technically incompetent 'experts,' any of whom can kill you with their bum dope. In his enormously popular book "How to Keep Your Volkswagen Alive..." the late John Muir tells his readers to scrape the cylinder with a Scout knife followed by 'polishing' the piston with sandpaper(!) '...and your troubles will be over.'(*) As will the useful life of the engine.
In fact, Volkswagen provides oil pressure/control pistons in two oversizes to compensate for wear in the cylinder. (As a point of interest, the reliability of any high-maintenance vehicle is primarily a reflection of the maintenance it receives.) All of the oil gallery sealing plugs must be removed. They are soft aluminum plugs, easily removed by drilling then threading a sheet metal screw into the hole and pulling the plug with a slap-hammer. Since these plugs will be replaced with threaded plugs it is standard practice to tap the bores now so that the cleaning can remove any swarf. Since the threaded plugs will see as much as 200 psi, particular care is taken in the tapping. (Installed with high strength Lok-tite, the threaded plugs are modified by filing a smooth, shallow scallop into their tops into which the parent metal of the crankcase will be straked using a round-nosed tool. I'll go into this in more detail when describing the engine's assembly.)
Lacking a suitable container for cold-tanking your crankcase, the next best option is a large tub, a good detergent such as 'Simple Green', plenty of hot water and copious amounts of elbow grease. When cleaning the crankcase you must pay particular attention to the parting line. This is a gasketless seal, a rather remarkable feature in a mass-produced article from the 1930's. Unfortunately, the sealing surface is a bit narrow by modern standards and is susceptible to leaking due to corrosion (on the lower parting line), minor scratches and 'shop rash' that occur in normal handling. So handle the crankcase with abnormal care.
Insure ALL of the old sealant is removed, not only from the parting line but the area around the cam plug, main oil seal and the drain-back channels associated with the #4 bearing and cam plug. When water is involved in the cleaning process you must insure the parts are perfectly DRY on completion. This is best accomplished by concluding the cleaning process with a boiling water rinse (and I mean literally boiling) followed by blowing all of the passages dry with compressed air.
The heads require further dismantling before being cleaned. See my posting in the archives of the VW engine group for the dismantling procedure. (http://www.escribe.com/aviation/vw/index.html?mID=6186 ) Given their importance, I prefer to treat heads as a special case, cleaning and overhauling them as a task apart from a major overhaul. Since your exhaust valves will need replacement or reseating about every 200 hours, you will find it more practical to provide yourself with four heads, all of equal chamber volume and valve geometry. This allows you to swap the heads and overhaul the pulled units at your leisure.
When dismantling used heads it is normal to discard the exhaust valves. (The relatively small (8mm) stems of VW valves are one of the weakest links in the engine's design, a fact easily confirmed by comparing them to the 10 and 11mm valve stems used in the Porsche or the half-inch [13mm] stems found in many aircraft engines.) You may also discard the stock adjusting screws, if so fitted. The remaining steel parts are to be cleaned as a group using carb cleaner & solvent, then lightly oiled and kept together for inspection. The head goes into the pail of carb cleaner for an overnight soak followed by a solvent rinse. In cleaning the heads do not use a wire brush in the chamber. We must inspect the chamber for cracks between the valve seats and the spark plug hole. Wire brushing can conceal such cracks.
The Woodruff key that aligns the pulley is removed using a BRASS drift no wider than the key to tap downward on the outboard end of the key. The front of the key will rock down, the back will rock up and you will eventually be able to remove WITH YOUR FINGERS. (Don't bugger up the Woodruff keys. They are a critical fit in their slots, both on the crankshaft and the parts they are used to align.) Put the Woodruff key in that Special Place along with the main bearing dowel pins. The cam- and distributor-gear are a shrink-fit on the crankshaft and serve to trap the #3 bearing. These parts are removed using a suitable press or puller. Do NOT try to do this job without the proper tools. A screw-type puller is available from most after-market VW retailers for about $30.
Use only solvent on the crankshaft. If inspection shows that a regrind is both required and possible, we will give it a better cleaning before sending it out (and an even more serious cleaning when we get it back).. Dismantling the crankshaft involves removal of the timing gear, distributor gear, the spacer between them and the Woodruff key which aligns them. You have already removed the Woodruff key for the pulley. The last items that need be removed are the four dowel pins that align the flywheel. Put all of the parts removed in that Special Place. (If the flywheel dowel pins refuse to come free, grasp them with a collet-type puller and vibrate the pulley-end of the crankshaft while maintaining a steady pull on the collet.
Use an air hammer fitted with a round-nosed tool, inserted into the threaded bore and making firm contact with the bottom. Wrapping tape around the tool to protect the threads is a good idea. If you don't have a collet-type puller, take a large pair of cheap import vise-grips, close the jaws and jig them true in the drill press or mill and drill a hole about .008 smaller than the dowel pins, centered on the jaws. Now use the modified vise-grips as your collet. [The jaws of most imported visegrips are not hardened and may be easily drilled.])
Clean the cam with solvent, oil it and put it aside for inspection.
If the rods are caked with baked-on oil you may boil them in TSP. Normally, a simple solvent wash is sufficient.
Wash the oil pump with solvent and inspect the pump body for scoring. On a proper overhaul the old oil pump is normally discarded. The best oil pump for the VW engine is the stock unit made by Bilstein. Over the years, Volkswagen used nine different oil pumps in the Type I engine. The oil pump is specific to the cam gear, with later model (ie, larger) pumps requiring the use of a dish-faced cam gear. Avoid after-market oil pumps, especially those having a cast-iron body. To insure proper sealing of the pump's inlet, the oil pump body is a .003 interference fit in the crankcase. The different coefficient of expansion between cast iron and magnesium alloy makes such pumps a very poor choice.