Ford Explorer, Maintaince And Repair Manual, Page: 451 / 1119

With the engine cold, locate and remove the oil pressure sending unit. 1.
Following the manufacturer's instructions, connect a mechanical oil pressure gauge and, if necessary,
a tachometer to the engine. 2.
Start the engine and allow it to idle. 3.
Check the oil pressure reading when cold and record the number. You may need to run the engine at a
specified rpm, so check the specifications. 4.
Run the engine until normal operating temperature is reached (upper radiator hose will feel warm). 5.
Check the oil pressure reading again with the engine hot and record the number. Turn the engine
OFF
.
6.
Compare your hot oil pressure reading to specification. If the reading is low, check the cold pressure
reading against the chart. If the cold pressure is well above the specification, and the hot reading was
lower than the specification, you may have the wrong viscosity oil in the engine. Change the oil,
making sure to use the proper grade and quantity, then repeat the test. 7.
Low oil pressure readings could be attributed to internal component wear, pump related problems, a low oil
level, or oil viscosity that is too low. High oil pressure readings could be caused by an overfilled crankcase,
too high of an oil viscosity or a faulty pressure relief valve.
Buy or Rebuild?
Now if you have determined that your engine is worn out, you must make some decisions. The question of
whether or not an engine is worth rebuilding is largely a subjective matter and one of personal worth. Is the
engine a popular one, or is it an obsolete model? Are parts available? Will it get acceptable gas mileage once
it is rebuilt? Is the car it's being put into worth keeping? Would it be less expensive to buy a new engine, have
your engine rebuilt by a pro, rebuild it yourself or buy a used engine from a salvage yard? Or would it be
simpler and less expensive to buy another car? If you have considered all these matters, and have still decided
to rebuild the engine, then it is time to decide how you will rebuild it.
The editors at Chilton feel that most engine machining should be performed by a professional machine
shop. Think of it as an assurance that the job has been done right the first time. There are many
expensive and specialized tools required to perform such tasks as boring and honing an engine block or
having a valve job done on a cylinder head. Even inspecting the parts requires expensive micrometers
and gauges to properly measure wear and clearances. A machine shop can deliver to you clean, and
ready to assemble parts, saving you time and aggravation. Your maximum savings will come from
performing the removal, disassembly, assembly and installation of the engine and purchasing or renting
only the tools required to perform these tasks.
A complete rebuild or overhaul of an engine involves replacing all of the moving parts (pistons, rods,
crankshaft, camshaft, etc.) with new ones and machining the non−moving wearing surfaces of the block and
heads. Unfortunately, this may not be cost effective. For instance, your crankshaft may have been damaged or
worn, but it can be machined undersize for a minimal fee.
So although you can replace everything inside the engine, it is usually wiser to replace only those parts which
are really needed, and, if possible, repair the more expensive ones. Later in this section, we will break the
engine down into its two main components: the cylinder head and the engine block. We will discuss each
component, and the recommended parts to replace during a rebuild on each.
Engine Overhaul Tips
Most engine overhaul procedures are fairly standard. In addition to specific parts replacement procedures and
specifications for your individual engine, this section is also a guide to acceptable rebuilding procedures.
Examples of standard rebuilding practice are given and should be used along with specific details concerning
HOW TO USE THIS BOOK
OIL PRESSURE TEST 445