Not all parts need cleaning. Careless cleaning can cause damage, either directly (eg. due to breakage), or indirectly (eg. oil dispersing cleaning fluids finding their way into the gearbox/engine). Unless a concours finish is essential, consider wiping dirt and grime away or scraping oil-soaked mud from parts.
Baby wipes are a cheap, plentiful, and extremely effective way to achieve cleaning of parts in-situ with a low risk of damaging or defacing anything hidden underneath (eg. brass identity plates). A wooden spatula or blunt stick makes an excellent mud removing device for cleaning the chassis, and a small wire brush should only be required for very stubborn dirt or rust removal.
When considering restoring paintwork or other finishes to parts, consider how difficult the part is to remove, restore and replace. It may be easier to effect an improvement to the current finish than to 'properly' restore the part.
As an example, take the steering column and wheel, both of which should be painted black and are often scratched or chipped. Whilst removal of the steering column may not seem overly complex, replacing it after re-painting often results in more scratching and damage to the work. A much better finish can be obtained by cleaning and painting in-situ (and consider also the final visibility of this part).
The steering wheel, on the other hand, is far better re-lacquered after removal. Engine lacquer is ideally suited for this task, giving a thick, smooth, gloss, finish which covers imperfections well and does not hold brush strokes.
It is not always possible to clean parts in-situ, or more thorough cleaning may be required. An ultrasonic bath may seem the ideal tool, especially for delicate parts such as the carburettor. The bath tank should ideally be a cube and not the very shallow baths sometimes seem for sale, which are underpowered and totally unsuitable for cleaning automotive parts. A 5" cube should be considered a minimum useful size (4.3/4"x5"x4.1/2" was found to be adequate in the following trials). Expect prices to be in the region of £80 to £100 (2007).
The bath kit as supplied, is typically not suitable for cleaning automotive parts (since this is rarely the intended function). A metal basket may have been provided (sometimes no basket) and this should, on no account, be used. It is crucial that no dirt, no matter how small, be allowed in contact with the stainless steel tank for extended periods of time since the vibration will cause the particles to erode the tank lining. To prevent this, it is necessary to construct an inner tank, usually a plastic or glass container, which is fixed such that no part of it comes in contact with the outer tank below the water line. Dirt and cleaning chemicals are now contained in the inner tank and clean water between the outer and inner tanks transmits the ultrasound to the inner tank.
To use the bath effectively, place the part to be cleaned in the inner tank, with a cleaning agent, most probably being white spirit, covering the part. Between the inner and outer tanks, fill with clean water, such that the water level is slightly higher than the level of the fluid in the inner tank (to maximize transmission of the ultrasound to the inner tank). After ensuring that no part of the inner tank is in contact with the outer tank below this water line, activate the bath for a period of 5 minutes. This is usually sufficient for most cleaning, altho occasionally a longer 10 minute period may be desirable. Resist the urge to leave the tank on for extended periods of time - this will very seriously shorten the lifespan of the transducer. If, after 10 minutes, the part is not clean, consider using a different cleaning agent, or different method of cleaning.
The orientation of the part is critical to achieving the best cleaning action, and it is often necessary to rotate the part during the cleaning process for best results. Be particularly careful not to create pockets of trapped air when placing the parts in the tank, since only the liquids will transmit the ultrasound.
An ultrasonic bath was tested on various LD10 parts against the more traditional approach of 'toothbrush and bucket of white spirit'. The parts tested were - 2 carburettors, an oil filter element, a collection of small screws, washers, bolts and other fixings, including some brass parts, rusted exhaust brackets. The cleaning solutions tested were water with washing-up liquid, harsh bathroom cleaning liquids (containing bleach and acid and marked as being totally unsuitable for use on metals), and white spirit.
Of these, the carburettors cleaned best in the harsh cleaning liquid and after 5 minutes the transformation was spectacular and the finish very professional. The float chamber and emulsion block cleaned perfectly, the body had to be cleaned in stages (it was too large to fit entirely in the tank). It would, of course, have been quite possible to clean and achieve very respectable results with the 'old fashioned' method however.
The oil filter element had seen 50,000 miles without cleaning and was badly distorted and no longer functioning efficiently as a filter. After straightening with an old scaffold pole, the filter was cleaned by soaking and agitating in 4 pints of white spirit (the 'old-fashioned' way). For comparison, it was then treated to 10 minutes in the ultrasonic bath with white spirit. Unfortunately, a before and after photo looked identical, but the amount of oil removed, per pint of white spirit, was approximately 4 to 5 times greater with the ultrasonic bath. The filter might be suitable for a few more miles now, but it is clearly cheaper to buy a new filter than the white spirit needed to clean the filter thoroughly.
All screws, bolts, washers, including brass parts, cleaned extremely well, altho there are cheaper ways to clean such parts. The brass gauze used for filters in the carburettor and fuel pump did not clean however, possibly due to the very fine mesh being quite badly blocked by 'gummy' petrol deposits. Repeated cleaning did not help, and it was necessary to use a toothbrush to clean these parts.
Corrosion and especially rust, were not affected significantly, altho longer periods and harsher cleaning agents will apparently help and will even strip the plating off chrome and other plated parts. Be particularly aware of this if using a more powerful bath.
Whilst the ultrasonic bath tested was not of sufficient size or power to tackle the more serious and demanding jobs required for cleaning automotive parts, it was still a useful tool. However, for £100, perhaps a very pretty girl in a French maid's outfit could be hired to clean for you instead.