Engine block repair has become increasingly important in car mechanics in recent years. The thin wall casting and high operating temperatures in many modern engines means that cracks are a much more common occurrence.
Additionally, where previously it was often cheaper to replace a head than repair a crack, finding rebuildable cylinder heads for late period engines is becoming increasingly difficult. For auto mechanics, this means that heads which they would have thrown away a few years ago now require lengthy, careful repair.
Engine block repair is quite complex, but bearing in mind a few basic points about assessing an engine, and some the different methods of repair, will help students get a firmer grasp on the topic.
Inspecting and Assessing Engine Blocks: Car Mechanic Training Basics
Cracked engine blocks occur due to excess heat, which can be caused by low coolant levels, water pump failure, overpowering, or casting failure. Cracks can often be identified by visual inspection, but students in mechanic training schools are taught to look out for other signs, such as excess engine smoke or signs of oil in the antifreeze. Cracks need to be closely inspected to determine how deep they are, and the location and metal type will also help determine which repair technique is required.
Intro To Pinning Techniques For Students In Mechanic Training Schools
80 per cent of cracks in cast iron heads or blocks can be repaired with iron or steel pins, though this process is less effective on aluminum heads, as it is a softer metal. Pinning requires no heat, so is less time consuming than welding, which makes it much more popular choice among mechanics. It also carries no risk of warping the casting.
Students pursuing car mechanic training will learn how to apply a number of different types of threaded pins and tapered plugs. Straight threaded pins are installed by drilling, tapping, and screwing pins into slightly overlapping holes to lock them in place. A heat resistant thread sealer is then applied to seal the crack fully.
Tapered pins are installed similarly but wedge themselves into the hole as they are tightened, with the tops being cut off once they have been fit. Small locks can be placed along cracks to hold them together, and the tops of the pins must be preened over with a blunt tool to blend them into the surrounding metal. The head should be pressure tested to ensure there are no leaks.
Welding Techniques You’ll Encounter During Your Career in Car Mechanics
For cracks that can’t be pinned, there are different welding methods that can be used. In flame-spray welding, a mechanic fuses a nickel powder to the sides of the crack to fill it in. TIG welding, common for aluminum heads, uses argon or helium gas to create an inert gas shield, which is needed as aluminum forms an oxide coating when exposed to air. In extreme repairs, furnace welding can be used to recast damaged heads, though mastering this requires extensive specialized training.
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