Tech A says that when performing a cylinder leakage test, the piston should be positioned at bottom dead center. Tech B says that a blown head gasket would generally leak past the exhaust valve. Who is correct

The causes of low compression in an engine cylinder and leakage past the exhaust can be identified by performing mechanical tests on the engine

The correct technician is Tech B; Blown head gasket would generally leak past the exhaust valve

The reason for arriving at the above selection is as follows:

A cylinder leakage test is generally performed after there is an indication of low compression from one or more cylinders. The test allows the identification of the part of the cylinder that is leaking.

The cylinder that shows sign of low compression is often the location that the cylinder leakage test is performed, although, the test can be performed on every cylinder

A cylinder leakage test is valid only when

The temperature of engine is about the temperature range of the engine in operationThe cylinder under test is at the Top Dead Center (TDC) position, such that the position of the piston in the cylinder is at the top or highest point of its stroke

Therefore, the positioning of the piston in the bottom dead center during a leakage test as mentioned by Tech A  is not correct

The route of coolant in the engine are sealed by the cylinder head gasket, where there is a blown head gasket, the coolant will be allowed to leak into the cylinders and into the exhaust, causing white smoke and sweet odor of antifreeze

Therefore, Tech B is correct, coolant leakage into the exhaust is an indication of a blown head gasket

Learn more about engine mechanical testing here:

Where is the rest of the information?

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