Measure the bore in the cylinder block, with a dialindicating bore gauge, to determine if wear or anout-of-round condition exceeds the manufacturer’sspecification. Figure 3-2 illustrates the use of a boregauge to measure a cylinder bore. You can use an insidemicrometer as well, but a dial indicating bore gauge iseasier to use.Inspect and measure the engine block’s hold-downbolt holes. Use a telescoping snap gauge to determine ifwear has caused enlargement of the holes. If atelescoping snap gauge is not available, try to move eachbolt from side to side with your fingers. If a bolt movesfrom side to side, its hole has enlarged and must berepaired. Always follow the manufacturer’s instructionson how to correct a hole enlargement problem.DYE PENETRANT TESTConduct a preliminary dye penetrant test on theengine block’s surface to identify cracks that you cannotsee otherwise. Be sure to follow the manufacturer’sinstructions on how to conduct this test. Remember thatonly a certified nondestructive testing technician canperform a dye penetrant test that meets the requirementsof quality assurance.AIR AND WATER PRESSURE TESTSTest the cylinder block for cracks in the cylinderbores between the water jacket and the oil passages byusing either air pressure or water pressure. The purposeof each test is to pressurize the water Jacket to the point,within safe limits, that leaks show.Figure 3-2.—Checking the cylinder bore for wear orout-of-roundness.Air Pressure TestBefore you perform the air pressure test, make sureyou completely strip and clean the block. Then, followthese basic procedures:1. Seal all of the block’s freshwater passages withgaskets and flanges.2. Connect a low-pressure air hose to a fixture onone of the flanges.3. Immerse the block into a tank of water heated tothe engine’s normal operating temperature. Allow theengine to soak for approximately 20 to 40 minutes, asspecified by the manufacturer. This allows the block towarm to the temperature of the water.4. Apply approximately 40 psi of pressure to theblock and watch for bubbles. Bubbles indicate a crackor leak in the block. Determine what repair is needed orcan be made when you identify the source of thebubbles.If you cannot dip the block, you may still performthe air pressure test. Attach the hose to a fixture securedto an opening to the water jacket. Pressurize the waterjacket. Carefully spray soapy water over the block andlook for air bubbles caused by the pressurized air.Water Pressure TestThe water pressure test is similar to the air pressuretest, except that defects are indicated by water leaksrather than by air leaks. Before you perform the waterpressure test, strip and clean the block Then, followthese procedures:1. Seal off all but one of the freshwater openingswith flanges and gaskets. Make seals airtight.2. Fill the water jacket with fresh water until all airis purged from the water jacket. Seal the fill openingwith a flange that contains an air hose coupling.3. Attach an air hose and pressurize the waterjacket to approximately 40 psi (see the manufacturer’smanual). Maintain the pressure in the water jacket for atleast 2 hours.4. Inspect the cylinder bores, air box, oil passages,crankcase, and cylinder block exterior for the presenceof water. The presence of water at any of these locationsindicates that the water jacket has one or more defects.3-2
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