1991 1999 ford explorer chilton User Manual

							
INSPECTION
Now that the engine block and all of its components are clean, its time to inspect them for wear and/or
damage. To accurately inspect them, you will need some specialized tools:
Two or three separate micrometers to measure the pistons and crankshaft journals
· 
A dial indicator
· 
Telescoping gauges for the cylinder bores
· 
A rod alignment fixture to check for bent connecting rods
· 
If you do not have access to the proper tools, you may want to bring the components to a shop that does.
Generally, you shouldnt expect cracks in the engine block or its components unless it was known to leak,
consume or mix engine fluids, it was severely overheated, or there was evidence of bad bearings and/or
crankshaft damage. A visual inspection should be performed on all of the components, but just because you
dont see a crack does not mean it is not there. Some more reliable methods for inspecting for cracks include
Magnaflux®, a magnetic process or Zyglo®, a dye penetrant. Magnaflux® is used only on ferrous metal (cast
iron). Zyglo® uses a spray on fluorescent mixture along with a black light to reveal the cracks. It is strongly
recommended to have your engine block checked professionally for cracks, especially if the engine was
known to have overheated and/or leaked or consumed coolant. Contact a local shop for availability and
pricing of these services.
Engine Block
ENGINE BLOCK BEARING ALIGNMENT
Remove the main bearing caps and, if still installed, the main bearing inserts. Inspect all of the main bearing
saddles and caps for damage, burrs or high spots. If damage is found, and it is caused from a spun main
bearing, the block will need to be align-bored or, if severe enough, replacement. Any burrs or high spots
should be carefully removed with a metal file.
Place a straightedge on the bearing saddles, in the engine block, along the centerline of the crankshaft. If any
clearance exists between the straightedge and the saddles, the block must be align-bored.
Align-boring consists of machining the main bearing saddles and caps by means of a flycutter that runs
through the bearing saddles.
DECK FLATNESS
The top of the engine block where the cylinder head mounts is called the deck. Insure that the deck surface is
clean of dirt, carbon deposits and old gasket material. Place a straightedge across the surface of the deck along
its centerline and, using feeler gauges, check the clearance along several points. Repeat the checking
procedure with the straightedge placed along both diagonals of the deck surface. If the reading exceeds 0.003
in. (0.076mm) within a 6.0 in. (15.2cm) span, or 0.006 in. (0.152mm) over the total length of the deck, it must
be machined.
CYLINDER BORES
The cylinder bores house the pistons and are slightly larger than the pistons themselves. A common
piston-to-bore clearance is 0.0015-0.0025 in. (0.0381mm-0.0635mm). Inspect and measure the cylinder
bores. The bore should be checked for out-of-roundness, taper and size. The results of this inspection will
determine whether the cylinder can be used in its existing size and condition, or a rebore to the next oversize
is required (or in the case of removable sleeves, have replacements installed). HOW TO USE THIS BOOK
INSPECTION 475 
						

							Use a telescoping gauge to measure the cylinder bore diameter-take several readings within the
same bore
The amount of cylinder wall wear is always greater at the top of the cylinder than at the bottom. This wear is
known as taper. Any cylinder that has a taper of 0.0012 in. (0.305mm) or more, must be rebored.
Measurements are taken at a number of positions in each cylinder: at the top, middle and bottom and at two
points at each position; that is, at a point 90 degrees from the crankshaft centerline, as well as a point parallel
to the crankshaft centerline. The measurements are made with either a special dial indicator or a telescopic
gauge and micrometer. If the necessary precision tools to check the bore are not available, take the block to a
machine shop and have them mike it. Also if you dont have the tools to check the cylinder bores, chances are
you will not have the necessary devices to check the pistons, connecting rods and crankshaft. Take these
components with you and save yourself an extra trip.
For our procedures, we will use a telescopic gauge and a micrometer. You will need one of each, with a
measuring range which covers your cylinder bore size.
Position the telescopic gauge in the cylinder bore, loosen the gauges lock and allow it to expand.
1. 
Your first two readings will be at the top of the cylinder bore, then proceed to the middle and finally the
bottom, making a total of six measurements.
Hold the gauge square in the bore, 90 degrees from the crankshaft centerline, and gently tighten the
lock. Tilt the gauge back to remove it from the bore.
2. 
Measure the gauge with the micrometer and record the reading.
3. 
Again, hold the gauge square in the bore, this time parallel to the crankshaft centerline, and gently
tighten the lock. Again, you will tilt the gauge back to remove it from the bore.
4. 
Measure the gauge with the micrometer and record this reading. The difference between these two
readings is the out-of-round measurement of the cylinder.
5. 
Repeat steps 1 through 5, each time going to the next lower position, until you reach the bottom of the
cylinder. Then go to the next cylinder, and continue until all of the cylinders have been measured.
6. 
The difference between these measurements will tell you all about the wear in your cylinders. The
measurements which were taken 90 degrees from the crankshaft centerline will always reflect the most wear.
That is because at this position is where the engine power presses the piston against the cylinder bore the
hardest. This is known as thrust wear. Take your top, 90 degree measurement and compare it to your bottom,
90 degree measurement. The difference between them is the taper. When you measure your pistons, you will
compare these readings to your piston sizes and determine piston-to-wall clearance. HOW TO USE THIS BOOK
476 INSPECTION 
						

							
Crankshaft
Inspect the crankshaft for visible signs of wear or damage. All of the journals should be perfectly round and
smooth. Slight scores are normal for a used crankshaft, but you should hardly feel them with your fingernail.
When measuring the crankshaft with a micrometer, you will take readings at the front and rear of each journal,
then turn the micrometer 90 degrees and take two more readings, front and rear. The difference between the
front-to-rear readings is the journal taper and the first-to-90 degree reading is the out-of-round
measurement. Generally, there should be no taper or out-of-roundness found, however, up to 0.0005 in.
(0.0127mm) for either can be overlooked. Also, the readings should fall within the factory specifications for
journal diameters.
If the crankshaft journals fall within specifications, it is recommended that it be polished before being
returned to service. Polishing the crankshaft insures that any minor burrs or high spots are smoothed, thereby
reducing the chance of scoring the new bearings.
Pistons and Connecting Rods
PISTONS
The piston should be visually inspected for any signs of cracking or burning (caused by hot spots or
detonation), and scuffing or excessive wear on the skirts. The wrist pin attaches the piston to the connecting
rod. The piston should move freely on the wrist pin, both sliding and pivoting. Grasp the connecting rod
securely, or mount it in a vise, and try to rock the piston back and forth along the centerline of the wrist pin.
There should not be any excessive play evident between the piston and the pin. If there are C-clips retaining
the pin in the piston then you have wrist pin bushings in the rods. There should not be any excessive play
between the wrist pin and the rod bushing. Normal clearance for the wrist pin is approx. 0.001-0.002 in.
(0.025mm-0.051mm).
Measure the pistons outer diameter, perpendicular to the wrist pin, with a micrometer
Use a micrometer and measure the diameter of the piston, perpendicular to the wrist pin, on the skirt.
Compare the reading to its original cylinder measurement obtained earlier. The difference between the two
readings is the piston-to-wall clearance. If the clearance is within specifications, the piston may be used as is.
If the piston is out of specification, but the bore is not, you will need a new piston. If both are out of
specification, you will need the cylinder rebored and oversize pistons installed. Generally if two or more
pistons/bores are out of specification, it is best to rebore the entire block and purchase a complete set of
oversize pistons. HOW TO USE THIS BOOK
INSPECTION 477 
						

							
CONNECTING ROD
You should have the connecting rod checked for straightness at a machine shop. If the connecting rod is bent,
it will unevenly wear the bearing and piston, as well as place greater stress on these components. Any bent or
twisted connecting rods must be replaced. If the rods are straight and the wrist pin clearance is within
specifications, then only the bearing end of the rod need be checked. Place the connecting rod into a vice, with
the bearing inserts in place, install the cap to the rod and torque the fasteners to specifications. Use a
telescoping gauge and carefully measure the inside diameter of the bearings. Compare this reading to the rods
original crankshaft journal diameter measurement. The difference is the oil clearance. If the oil clearance is
not within specifications, install new bearings in the rod and take another measurement. If the clearance is still
out of specifications, and the crankshaft is not, the rod will need to be reconditioned by a machine shop.
You can also use Plastigage® to check the bearing clearances. The assembling section has complete
instructions on its use.
Camshaft
Inspect the camshaft and lifters/followers as described earlier in this section.
Bearings
All of the engine bearings should be visually inspected for wear and/or damage. The bearing should look
evenly worn all around with no deep scores or pits. If the bearing is severely worn, scored, pitted or heat
blued, then the bearing, and the components that use it, should be brought to a machine shop for inspection.
Full-circle bearings (used on most camshafts, auxiliary shafts, balance shafts, etc.) require specialized tools
for removal and installation, and should be brought to a machine shop for service.
Oil Pump
The oil pump is responsible for providing constant lubrication to the whole engine and so it is
recommended that a new oil pump be installed when rebuilding the engine.
Completely disassemble the oil pump and thoroughly clean all of the components. Inspect the oil pump gears
and housing for wear and/or damage. Insure that the pressure relief valve operates properly and there is no
binding or sticking due to varnish or debris. If all of the parts are in proper working condition, lubricate the
gears and relief valve, and assemble the pump.
REFINISHING
Almost all engine block refinishing must be performed by a machine shop. If the cylinders are not to be
rebored, then the cylinder glaze can be removed with a ball hone. When removing cylinder glaze with a ball
hone, use a light or penetrating type oil to lubricate the hone. Do not allow the hone to run dry as this may
cause excessive scoring of the cylinder bores and wear on the hone. If new pistons are required, they will need
to be installed to the connecting rods. This should be performed by a machine shop as the pistons must be
installed in the correct relationship to the rod or engine damage can occur. HOW TO USE THIS BOOK
478 INSPECTION 
						

							Use a ball type cylinder hone to remove any glaze and provide a new surface for seating the
piston rings
Pistons and Connecting Rods
Only pistons with the wrist pin retained by C-clips are serviceable by the home-mechanic. Press fit pistons
require special presses and/or heaters to remove/install the connecting rod and should only be performed by a
machine shop.
All pistons will have a mark indicating the direction to the front of the engine and the must be installed into
the engine in that manner. Usually it is a notch or arrow on the top of the piston, or it may be the letter F cast
or stamped into the piston.
Most pistons are marked to indicate positioning in the engine (usually a mark means the side facing the front)
C-CLIP TYPE PISTONS
Note the location of the forward mark on the piston and mark the connecting rod in relation.
1. 
Remove the C-clips from the piston and withdraw the wrist pin.
2.  HOW TO USE THIS BOOK
REFINISHING 479 
						

							
Varnish build-up or C-clip groove burrs may increase the difficulty of removing the wrist pin. If
necessary, use a punch or drift to carefully tap the wrist pin out.
Insure that the wrist pin bushing in the connecting rod is usable, and lubricate it with assembly lube.
3. 
Remove the wrist pin from the new piston and lubricate the pin bores on the piston.
4. 
Align the forward marks on the piston and the connecting rod and install the wrist pin.
5. 
The new C-clips will have a flat and a rounded side to them. Install both C-clips with the flat side
facing out.
6. 
Repeat all of the steps for each piston being replaced.
7. 
ASSEMBLY
Before you begin assembling the engine, first give yourself a clean, dirt free work area. Next, clean every
engine component again. The key to a good assembly is cleanliness.
Mount the engine block into the engine stand and wash it one last time using water and detergent
(dishwashing detergent works well). While washing it, scrub the cylinder bores with a soft bristle brush and
thoroughly clean all of the oil passages. Completely dry the engine and spray the entire assembly down with
an anti-rust solution such as WD-40® or similar product. Take a clean lint-free rag and wipe up any excess
anti-rust solution from the bores, bearing saddles, etc. Repeat the final cleaning process on the crankshaft.
Replace any freeze or oil galley plugs which were removed during disassembly.
Crankshaft Remove the main bearing inserts from the block and bearing caps.
1. 
If the crankshaft main bearing journals have been refinished to a definite undersize, install the correct
undersize bearing. Be sure that the bearing inserts and bearing bores are clean. Foreign material under
inserts will distort bearing and cause failure.
2. 
Place the upper main bearing inserts in bores with tang in slot.
3. 
The oil holes in the bearing inserts must be aligned with the oil holes in the cylinder block. Install the lower main bearing inserts in bearing caps.
4. 
Clean the mating surfaces of block and rear main bearing cap.
5. 
Carefully lower the crankshaft into place. Be careful not to damage bearing surfaces.
6. 
Check the clearance of each main bearing by using the following procedure: Place a piece of Plastigage® or its equivalent, on bearing surface across full width of bearing
cap and about  1
/4  in. off center.
1. 
7.  HOW TO USE THIS BOOK
480 ASSEMBLY 
						

							Apply a strip of gauging material to the bearing journal, then install and torque the cap
Install cap and tighten bolts to specifications. Do not turn crankshaft while Plastigage® is in
place.
2. 
Remove the cap. Using the supplied Plastigage® scale, check width of Plastigage® at widest
point to get maximum clearance. Difference between readings is taper of journal.
3.  HOW TO USE THIS BOOK
ASSEMBLY 481 
						

							After the cap is removed again, use the scale supplied with the gauging material to check the
clearance
If clearance exceeds specified limits, try a 0.001 in. or 0.002 in. undersize bearing in
combination with the standard bearing. Bearing clearance must be within specified limits. If
standard and 0.002 in. undersize bearing does not bring clearance within desired limits,
refinish crankshaft journal, then install undersize bearings.
4. 
After the bearings have been fitted, apply a light coat of engine oil to the journals and bearings. Install
the rear main bearing cap. Install all bearing caps except the thrust bearing cap. Be sure that main
bearing caps are installed in original locations. Tighten the bearing cap bolts to specifications.
8. 
Install the thrust bearing cap with bolts finger-tight.
9. 
Pry the crankshaft forward against the thrust surface of upper half of bearing.
10. 
Hold the crankshaft forward and pry the thrust bearing cap to the rear. This aligns the thrust surfaces
of both halves of the bearing.
11. 
Retain the forward pressure on the crankshaft. Tighten the cap bolts to specifications.
12. 
Measure the crankshaft end-play as follows:
13. 
A dial gauge may be used to check crankshaft end-playHOW TO USE THIS BOOK
482 ASSEMBLY 
						

							Mount a dial gauge to the engine block and position the tip of the gauge to read from the crankshaft
end.
1. 
Carefully pry the crankshaft toward the rear of the engine and hold it there while you zero the gauge.
Carefully pry the crankshaft back and forth while reading the dial gauge for end-play
2. 
Carefully pry the crankshaft toward the front of the engine and read the gauge.
3. 
Confirm that the reading is within specifications. If not, install a new thrust bearing and repeat the
procedure. If the reading is still out of specifications with a new bearing, have a machine shop inspect
the thrust surfaces of the crankshaft, and if possible, repair it.
4. 
Install the rear main seal.
14. 
Rotate the crankshaft so as to position the first rod journal to the bottom of its stroke.
15. 
Pistons and Connecting Rods Before installing the piston/connecting rod assembly, oil the pistons, piston rings and the cylinder
walls with light engine oil. Install connecting rod bolt protectors or rubber hose onto the connecting
rod bolts/studs. Also perform the following: Select the proper ring set for the size cylinder bore.
1. 
Position the ring in the bore in which it is going to be used.
2. 
Push the ring down into the bore area where normal ring wear is not encountered.
3. 
Use the head of the piston to position the ring in the bore so that the ring is square with the
cylinder wall. Use caution to avoid damage to the ring or cylinder bore.
4. 
Measure the gap between the ends of the ring with a feeler gauge. Ring gap in a worn
cylinder is normally greater than specification. If the ring gap is greater than the specified
limits, try an oversize ring set.
5. 
1.  HOW TO USE THIS BOOK
ASSEMBLY 483 
						

							Checking the piston ring-to-ring groove side clearance using the ring and a feeler gauge
Check the ring side clearance of the compression rings with a feeler gauge inserted between
the ring and its lower land according to specification. The gauge should slide freely around
the entire ring circumference without binding. Any wear that occurs will form a step at the
inner portion of the lower land. If the lower lands have high steps, the piston should be
replaced.
The notch on the side of the bearing cap matches the tang on the bearing insert
6.  HOW TO USE THIS BOOK
484 ASSEMBLY