Ford 2003 Mustang Workshop Manual page 847

6. Carry out an oil consumption test:
a. Drain the engine oil, remove the oil bypass filter (6714) and refill with one liter (quart) less than
the recommended amount.
b. Run the engine for three minutes (10 minutes if cold), and allow the oil to drain back for at least
five minutes with the vehicle on a level surface.
c. Remove oil level dipstick and wipe clean. (Do not wipe with anything contaminated with silicone
compounds.) Reinstall the oil level dipstick, being sure to seat it firmly in the oil level indicator
tube (6754). Remove the oil level dipstick and draw a mark on the back (unmarked) surface at
the indicated oil level. This level should be about the same as the MIN or ADD mark on the face
of the oil level dipstick.
d. Add one liter (quart) of oil. Restart the engine and allow to idle for at least two minutes. Shut off
the engine and allow the oil to drain back for at least five minutes. Mark the oil level dipstick,
using the procedure above.
e. Record the vehicle mileage.
f. Instruct the customer to drive the vehicle as usual and perform the following:
Check the oil level regularly at intervals of 160 to 240 km (100-150 miles).
Return to the service point when the oil level drops below the lower (MIN or ADD) mark
on the oil level dipstick.
Add only full liters (quarts) of the same oil in an emergency. Note the mileage at which
the oil is added.
g. Check the oil level under the same conditions and at the same location as in Steps 6c and 6d.
Measure the distance from the oil level to the UPPER mark on the oil level dipstick and
record.
Measure the distance between the two scribe marks and record.
Divide the first measurement by the second.
Divide the distance driven during the oil test by the result. This quantity is the
approximate oil consumption rate in kilometers per liter or in miles per quart.
h. If the oil consumption rate is unacceptable, go to Step 7.
7. Check the positive crankcase ventilation (PCV) system. Make sure the system is not plugged.
8. Check for plugged oil drain-back holes in the cylinder heads and cylinder block.
9. If the condition still exists after performing the above steps, go to Step 10.
10. Perform a cylinder compression test or perform a cylinder leak detection test with Engine
Cylinder Leak Detection/Air Pressurization Kit. This can help determine the source of oil
consumption such as valves, piston rings or other areas.
11. NOTE: After determining if new parts should be installed, make sure correct parts are used.
Check valve guides for excessive guide clearance. Install new all valve stem seals (6571) after
verifying valve guide clearance.
12. Worn or damaged internal engine components can cause excessive oil consumption. Small
deposits of oil on the tips of spark plugs can be a clue to internal oil consumption. If internal oil
consumption still persists, proceed as follows:
a. Remove the engine from the vehicle and place it on an engine work stand. Remove the intake
manifolds (9424), cylinder heads, oil pan (6675) and oil pump (6600).
b. Check piston ring clearance, ring gap and ring orientation. Repair as necessary.
c. Check for excessive bearing clearance. Repair as necessary.
13. Repeat the oil consumption test (Step 6) to confirm the oil consumption concern has been
resolved.