Cylinder Block and Head - Continued

Wheeled Vehicle Engines
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Small coolant leaks in the combustion chamber may be indicated by white smoke (steam) from the exhaust,

loss of coolant, engine overheating, and engine misfiring. To check for a small leak, either remove the

thermostat or operate the engine until the thermostat has opened. Remove the fan belts so the coolant pump

will not operate, and then fill the radiator all the way to the top.

Operate the engine and look for bubbles in the coolant at the radiator filler neck. If there are any bubbles,

there is a leak between a coolant passage and a combustion chamber. The bubbles are caused by pressure

leaking from the combustion chamber into the coolant during the compression and power strokes. Do not

operate the engine any longer than necessary to make this test as it will overheat very quickly with the fan belts

removed.

If the engine has an internal coolant leak, the problem is most likely a faulty head gasket or a cracked cylinder

block or head. The cylinder head will have to be removed to determine if these faults exist.

To test the sending unit, first run the engine until it has had time to warm up. If no reading is indicated on

the gage, remove the wire from the sending unit and momentarily ground the wire to the engine block. If the

gage now indicates, the temperature sending unit is faulty and must be replaced. If the gage still does not

indicate, the gage or wiring is probably defective.

If the gage or circuit is defective but still indicates, it will most likely read full scale. When the gage reads full

scale, disconnect the wire from the sending unit. If the gage pointer moves all the way to the cold position, the

sending unit is defective. If the pointer remains at full scale, the gage or wiring is defective.

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