Specifications

CONDITION POSSIBLE CAUSES CORRECTION
LUBRICATING OIL PRESSURE
LOW
1. Low oil level. 1a. Check and fill with clean engine oil.
1b. Check for severe external oil leaks that
could reduce the pressure.
2. Oil viscosity thin, diluted, or wrong
specification.
2. Verify the correct oil is being used. Check
for oil dilution.
3. Improperly operating pressure switch/gauge 3. Verify the pressure switch is functioning
correctly. If not, replace switch/gauge.
4. Relief valve stuck open. 4. Check/replace valve.
5. Plugged oil filter. 5. Change oil filter. Oil filter change interval
may need to be revised.
6. Oil cooler was replaced, shipping plugs left
in cooler.
6. Check/removed shipping plugs.
7. Worn oil pump. 7. Check/replace oil pump.
8. Suction tube loose or seal leaking. 8. Check and replace seal.
9. Worn bearing or wrong bearing installed. 9. Inspect and replace connecting rod or main
bearings. check and replace piston cooling oil
jet.
10. Oil jets under piston loose or bad fit. 10. Check oil jets position.
LUBRICATING OIL LOSS 1. External oil leaks. 1. Visually inspect for oil leaks. Repair as
required.
2. Crankcase being overfilled. 2. Verify that the correct dipstick is being used.
3. Incorrect oil specification or viscosity. 3a. Make sure the correct oil is being used.
3b. Look for reduced viscosity from dilution
with fuel.
3c. Review/reduce the oil change intervals.
4. Oil cooler leak. 4. Check and replace the oil cooler.
5. High blow-by forcing oil out the breather. 5. Check the breather tube area for signs of oil
loss.
LUBRICATING OIL LOSS (CONT.) 6. Turbocharger leaking oil into the air intake. 6. Inspect air duct for evidence of oil transfer.
7. Piston rings not sealing (oil being
consumed by the engine).
7. Perform blow-by check. Repair as required.
COMPRESSION KNOCKS 1. Air in fuel system. 1. Bleed the fuel system (refer to Group 14,
Fuel System).
2. Poor quality fuel or water/gasoline
contaminated fuel.
2. Verify by operating from a temporary tank
with good fuel. Clean and flush the fuel supply
tank. Replace fuel/water separator.
3. Engine Overloaded. 3. Verify the engine load rating is not being
exceeded.
4. Improperly operating injectors. 4. Check and replace injectors.
5. Fuel injection system defective. 5a. Instrumented injection. 5b. Timing solenoid
of the fuel pump. 5c. Pre and post heat time
of the glow plugs. Check the fault codes in the
ECU.
EXCESSIVE ENGINE NOISES 1. Drive belt squeal, insufficient tension or
abnormally high loading.
1. Inspect the drive belts. Make sure water
pump pulley, generator and power steering all
turn freely.
2. Intake air and exhaust leak. 2. Refer to excessive exhaust smoke. (Engine
Diagnosis and Testing)
3. Excessive valve lash. 3. Make sure the rocker arms are not bent.
Defective hydraulic lash adjuster.
4. Turbocharger noise. 4. Check turbocharger impeller and turbine
wheel for housing contact.
5. Power function knock. 5. Check and replace rod and main bearings.
6. Fuel injection system defective. 6a. Instrumented injection. 6b. Timing solenoid
of the fuel pump. 6c. Pre and post heat time
of the glow plugs. Check the fault codes in the
ECU.
HYDRAULIC TAPPETS
Before disassembling any part of the engine to cor-
rect tappet noise, check the oil pressure. If vehicle
has no oil pressure gauge, install a reliable gauge at
the pressure sending unit. The pressure should be
between 3.5 bars to 5.0 bars at 4000 RPM.
Check the oil level after the engine reaches normal
operating temperature. Allow 5 minutes to stabilize
NS/GS ENGINE 9 - 39
DIAGNOSIS AND TESTING (Continued)