LUBRICATING SYSTEM PROBLEM
troubleshoot an engine lubricating system, begin by gathering information on the problem.
Ask the operator questions. Analyze the symptoms using your understanding of system
operation. You should arrive at a logical deduction about the cause of the problem.
problems most often occur in the lubrication system are as follows:
oil consumption (oil must be added frequently)
oil pressure (gauge reads low, indicator light glows, or abnormal engine noises)
oil pressure (gauge reads high, oil filter swelled)
indicator or gauge circuit (inaccurate operation or readings)
diagnosing these troubles, make a visual inspection of the engine for obvious problems.
Check for oil leakage, disconnected sending unit wire, low oil level, damaged oil pan, or
other troubles that relate to the symptoms.
If the operator must add oil frequently to the engine, this is a symptom of high oil
consumption. External oil leakage out of the engine or internal leakage of oil into the
combustion chambers causes high oil consumption. A description of each of these problems
is as follows:
oil leakagedetected as darkened oil wet areas on or around the engine. Oil may also
be found in small puddles under the vehicle. Leaking gaskets or seals are usually the
source of external engine oil leakage.
oil leakageshows up as blue smoke exiting the exhaust system of the vehicle. For
example, if the engine piston rings and cylinders are badly worn, oil can enter the
combustion chambers and will be burned during combustion
Do not confuse black smoke (excess fuel in the cylinder) and white smoke
(water leakage into the engine cylinder) with blue smoke caused by engine oil.
Low oil pressure is indicated when the oil indicator light glows, oil gauge reads low,
or when the engine lifters or bearings rattle. The most common causes of low oil pressure
are as follows:
oil level (oil not high enough in pan to cover oil pickup)
connecting rod or main bearings (pump cannot provide enough oil volume)
or diluted oil (low viscosity or fuel in the oil)
or broken pressure relief valve spring (valve opening too easily)
or loose pump pickup tube (air being pulled into the oil pump)
oil pump (excess clearance between rotor or gears and housing)
oil pickup screen (reduce amount of oil entering pump)
A low oil
level is a common cause of low oil pressure. Always check the oil level first when
troubleshooting a low oil pressure problem.
High oil pressure is seldom a problem. When it occurs, the oil pressure gauge will
read high. The most frequent causes of high oil pressure are as follows:
relief valve struckopen (not opening at specified pressure)
High relief valve spring tension (strong spring or spring has been improperly shimmed)
High oil viscosity (excessively thick oil or use of oil additive that increases viscosity)
Restricted oil gallery (defective block casting or debris in oil passage)
or Gauge Problems
A bad oil pressure indicator or gauge may scare the operator into believing there are
major problems. The indicator light may stay on or flicker, pointing to a low oil pressure
problem. The gauge may read low or high, also indicating a lubrication system problem.
indicator or gauge circuit for problems. The wire going to the sending unit may have
fallen off. The sending unit wire may also be shorted to ground (light stays on or gauge
always reads high).
To check the
action of the indicator or gauge, remove the wire from the sending unit. Touch it on a
metal part of the engine. This should make the indicator light glow or the oil pressure
gauge read maximum. If it does, the sending unit may be defective. If it does not, then
the circuit, indicator, or gauge may be faulty.
Always check the service manual before testing an indicator or gauge
circuit. Some manufacturers recommend a special gauge tester. This is especially important
with some computer-controlled systems.