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Making Dollars and Sense Cleaning Blocks, Heads

While it can be difficult to rank the most important part of the engine rebuild process, consideration certainly has to be given to the cleaning process.

By Doug Kaufman

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Unless you’re starting with all new parts, cleaning is as important to your engine build as disassembly, inspection, machining and reassembly.

Without taking the cylinder heads and engine blocks down to bare metal, you can’t properly inspect the castings for cracks, wear and other defects.

For something so important, proper cleaning technique is often misunderstood, overlooked or ignored altogether. Of course, doing it right can be a significant part of your business expense – but doing it wrong can be even more costly.

Effective cleaning is often critical to the successful completion of remanufacturing. Customers expect clean parts and such parts generally perform better. The right cleaning equipment for the job can also free up personnel to perform other tasks while providing improved cleaning results.

If you can reduce the need to dispose of used chemicals, that can be significant savings, too. And if you can maximize your shop space by not having to isolate cleaning processes from the rest of the operation it’s definitely a savings.

A reduction in the amount of cleaning product you use can also save you money.

Newer techniques allow the use of water with various media to cushion the media, resulting in lower a consumption rate. Speed reductions, while realistic, are not typically noticeable to the average user.

Technology allows for even more accuracy. Automatic methods (or at least hands-off) can help speed up cleaning times. Process timers can help ensure standard and uniform practices and minimize human error; automatic chemistry control can monitor the chemistry’s concentration and add required amounts when needed; rinse quality can be monitored automatically and maintained as needed.

How clean is clean enough? It’s perhaps in the eye of the beholder – improper cleaning won’t necessarily save you money. If you’re cleaning the surface grime but damaging related components or leaving traces of the cleaning product that can eventually cause significant engine damage, the system is likely not right for your needs.

Time is money, so if a shop can implement an effective piece of cleaning equipment to allow them to free up the manual aspect of cleaning, it obviously saves cost and increases profit. But if equipment is purchased without careful consideration it could end up costing you more in the long run.

The most common mistake, say experts, is trying to clean parts with existing equipment intended for the wrong application. It’s always better to invest in the correct equipment for the job – the investment is actually in a versatile tool that can benefit your shop’s bottom line.

What Are Your Choices?
Simply put, the correct cleaning process is the one that removes all of the dirt, grease, oil, rust, scale and carbon deposits that have built up on heads or blocks over the years. If you’re working with painted castings, the old paint will need to be stripped away so the surface can be repainted.

Even if you’re working with brand new castings, a final cleaning is still necessary after you’ve completed your machining procedures to remove residual traces of oil, metal chips and honing residue.

Getting to the final clean requires decisions to be made. Depending on the cleaning solution or chemicals used, dirt, oil and grease are all soluble to some extent. Chemical solvents may be very effective cleaning agents, but rules that limit the release of Volatile Organic Compounds (VOCs) into the atmosphere mean their use may be limited.

Aqueous cleaning solutions that contain detergents or alkalines have replaced many solvents, and typically require a certain amount of heat (130 to 170 degrees F) and agitation to clean effectively.

Cleaning heads and blocks can be a challenge for a number of reasons. The castings have intricate contours, complex geometries and both interior and exterior surfaces that have to be cleaned.  However, whether the castings are iron or aluminum makes no difference – both have to be cleaned down to a bare metal surface and those surfaces may be difficult to reach.

Different metals may require somewhat different cleaning techniques depending on the method(s) that are being used. Aluminum and cast iron react differently to chemical cleaning solutions, abrasives and heat.

The water jackets inside the heads and block may be lined with  rust, scale or sediment and blind holes can trap debris. Oil lines inside the block may be contaminated with sludge and varnish deposits. Combustion chambers and ports are usually coated with hard carbon deposits. Iron castings typically have a layer of paint underneath the grease and dirt, which may, in turn, be covering rust.

A highly caustic solution in a hot tank or spray washer can effectively remove most contaminants from iron heads and blocks. But if the same solution is used on aluminum, it may be too strong and can etch or discolor the metal.

Conversely, if a milder aluminum-appropriate cleaning solution is used on cast iron, it may take much longer to achieve the same results. There are cleaning solutions and chemicals that are said to work effectively on both types of metal, but some shops prefer to use a dedicated cleaning process for each type of metal.