1991 1999 ford explorer chilton User Manual

							Use a micrometer to check the valve stem diameter
Springs, Retainers and Valve Locks
The first thing to check is the most obvious, broken springs. Next check the free length and squareness of each
spring. If applicable, insure to distinguish between intake and exhaust springs. Use a ruler and/or carpenters
square to measure the length. A carpenters square should be used to check the springs for squareness. If a
spring pressure test gauge is available, check each springs rating and compare to the specifications chart.
Check the readings against the specifications given. Any springs that fail these inspections should be replaced.
The spring retainers rarely need replacing, however they should still be checked as a precaution. Inspect the
spring mating surface and the valve lock retention area for any signs of excessive wear. Also check for any
signs of cracking. Replace any retainers that are questionable.
Valve locks should be inspected for excessive wear on the outside contact area as well as on the inner notched
surface. Any locks which appear worn or broken and its respective valve should be replaced.
Use a caliper to check the valve spring free-lengthHOW TO USE THIS BOOK
INSPECTION 465 
						

							Check the valve spring for squareness on a flat surface; a carpenters square can be used
Cylinder Head
There are several things to check on the cylinder head: valve guides, seats, cylinder head surface flatness,
cracks and physical damage.
VALVE GUIDES
Now that you know the valves are good, you can use them to check the guides, although a new valve, if
available, is preferred. Before you measure anything, look at the guides carefully and inspect them for any
cracks, chips or breakage. Also if the guide is a removable style (as in most aluminum heads), check them for
any looseness or evidence of movement. All of the guides should appear to be at the same height from the
spring seat. If any seem lower (or higher) from another, the guide has moved. Mount a dial indicator onto the
spring side of the cylinder head. Lightly oil the valve stem and insert it into the cylinder head. Position the
dial indicator against the valve stem near the tip and zero the gauge. Grasp the valve stem and wiggle towards
and away from the dial indicator and observe the readings. Mount the dial indicator 90 degrees from the initial
point and zero the gauge and again take a reading. Compare the two readings for an out of round condition.
Check the readings against the specifications given. An Inside Diameter (I.D.) gauge designed for valve
guides will give you an accurate valve guide bore measurement. If the I.D. gauge is used, compare the
readings with the specifications given. Any guides that fail these inspections should be replaced or machined. HOW TO USE THIS BOOK
466 INSPECTION 
						

							A dial gauge may be used to check valve stem-to-guide clearance; read the gauge while
moving the valve stem
VALVE SEATS
A visual inspection of the valve seats should show a slightly worn and pitted surface where the valve face
contacts the seat. Inspect the seat carefully for severe pitting or cracks. Also, a seat that is badly worn will be
recessed into the cylinder head. A severely worn or recessed seat may need to be replaced. All cracked seats
must be replaced. A seat concentricity gauge, if available, should be used to check the seat run-out. If run-out
exceeds specifications the seat must be machined (if no specification is available given use 0.002 in. or
0.051mm).
CYLINDER HEAD SURFACE FLATNESS
After you have cleaned the gasket surface of the cylinder head of any old gasket material, check the head for
flatness.
Check the head for flatness across the center of the head surface using a straightedge and feeler gauge
HOW TO USE THIS BOOK
INSPECTION 467 
						

							Checks should also be made along both diagonals of the head surface
Place a straightedge across the gasket surface. Using feeler gauges, determine the clearance at the center of
the straightedge and across the cylinder head at several points. Check along the centerline and diagonally on
the head surface. If the warpage 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 head, the cylinder head must be resurfaced. After resurfacing the heads
of a V-type engine, the intake manifold flange surface should be checked, and if necessary, milled
proportionally to allow for the change in its mounting position.
CRACKS AND PHYSICAL DAMAGE
Generally, cracks are limited to the combustion chamber, however, it is not uncommon for the head to crack
in a spark plug hole, port, outside of the head or in the valve spring/rocker arm area. The first area to inspect is
always the hottest: the exhaust seat/port area.
A visual inspection should be performed, 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) heads. Zyglo® uses a spray on
fluorescent mixture along with a black light to reveal the cracks. It is strongly recommended to have your
cylinder head 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.
Physical damage is usually very evident. For example, a broken mounting ear from dropping the head or a
bent or broken stud and/or bolt. All of these defects should be fixed or, if unrepairable, the head should be
replaced.
Camshaft and Followers
Inspect the camshaft(s) and followers as described earlier in this section.
REFINISHING & REPAIRING
Many of the procedures given for refinishing and repairing the cylinder head components must be performed
by a machine shop. Certain steps, if the inspected part is not worn, can be performed yourself inexpensively.
However, you spent a lot of time and effort so far, why risk trying to save a couple bucks if you might have to
do it all over again? HOW TO USE THIS BOOK
468 INSPECTION 
						

							
Valves
Any valves that were not replaced should be refaced and the tips ground flat. Unless you have access to a
valve grinding machine, this should be done by a machine shop. If the valves are in extremely good condition,
as well as the valve seats and guides, they may be lapped in without performing machine work.
It is a recommended practice to lap the valves even after machine work has been performed and/or new valves
have been purchased. This insures a positive seal between the valve and seat.
LAPPING THE VALVES
Before lapping the valves to the seats, read the rest of the cylinder head section to insure that any
related parts are in acceptable enough condition to continue. Also, remember that before any valve seat
machining and/or lapping can be performed, the guides must be within factory recommended
specifications.
Invert the cylinder head.
1. 
Lightly lubricate the valve stems and insert them into the cylinder head in their numbered order.
2. 
Raise the valve from the seat and apply a small amount of fine lapping compound to the seat.
3. 
Moisten the suction head of a hand-lapping tool and attach it to the head of the valve.
4. 
Rotate the tool between the palms of both hands, changing the position of the valve on the valve seat
and lifting the tool often to prevent grooving.
5. 
Lap the valve until a smooth, polished circle is evident on the valve and seat.
6. 
Remove the tool and the valve. Wipe away all traces of the grinding compound and store the valve to
maintain its lapped location.
7. 
WARNING
Do not get the valves out of order after they have been lapped. They must be put back with the same valve
seat with which they were lapped.
Springs, Retainers and Valve Locks
There is no repair or refinishing possible with the springs, retainers and valve locks. If they are found to be
worn or defective, they must be replaced with new (or known good) parts.
Cylinder Head
Most refinishing procedures dealing with the cylinder head must be performed by a machine shop. Read the
sections below and review your inspection data to determine whether or not machining is necessary.
VALVE GUIDE
If any machining or replacements are made to the valve guides, the seats must be machined.
Unless the valve guides need machining or replacing, the only service to perform is to thoroughly clean them
of any dirt or oil residue.
There are only two types of valve guides used on automobile engines: the replaceable-type (all aluminum
heads) and the cast-in integral-type (most cast iron heads). There are four recommended methods for
repairing worn guides.
Knurling
· 
Inserts
· 
Reaming oversize
· 
Replacing
·  HOW TO USE THIS BOOK
REFINISHING & REPAIRING 469 
						

							
Knurling is a process in which metal is displaced and raised, thereby reducing clearance, giving a true center,
and providing oil control. It is the least expensive way of repairing the valve guides. However, it is not
necessarily the best, and in some cases, a knurled valve guide will not stand up for more than a short time. It
requires a special knurlizer and precision reaming tools to obtain proper clearances. It would not be cost
effective to purchase these tools, unless you plan on rebuilding several of the same cylinder head.
Installing a guide insert involves machining the guide to accept a bronze insert. One style is the coil-type
which is installed into a threaded guide. Another is the thin-walled insert where the guide is reamed oversize
to accept a split-sleeve insert. After the insert is installed, a special tool is then run through the guide to
expand the insert, locking it to the guide. The insert is then reamed to the standard size for proper valve
clearance.
Reaming for oversize valves restores normal clearances and provides a true valve seat. Most cast-in type
guides can be reamed to accept an valve with an oversize stem. The cost factor for this can become quite high
as you will need to purchase the reamer and new, oversize stem valves for all guides which were reamed.
Oversizes are generally 0.003-0.030 in. (0.076-0.762mm), with 0.015 in. (0.381mm) being the most
common.
To replace cast-in type valve guides, they must be drilled out, then reamed to accept replacement guides. This
must be done on a fixture which will allow centering and leveling off of the original valve seat or guide,
otherwise a serious guide-to-seat misalignment may occur making it impossible to properly machine the seat.
Replaceable-type guides are pressed into the cylinder head. A hammer and a stepped drift or punch may be
used to install and remove the guides. Before removing the guides, measure the protrusion on the spring side
of the head and record it for installation. Use the stepped drift to hammer out the old guide from the
combustion chamber side of the head. When installing, determine whether or not the guide also seals a water
jacket in the head, and if it does, use the recommended sealing agent. If there is no water jacket, grease the
valve guide and its bore. Use the stepped drift, and hammer the new guide into the cylinder head from the
spring side of the cylinder head. A stack of washers the same thickness as the measured protrusion may help
the installation process.
VALVE SEATS
Before any valve seat machining can be performed, the guides must be within factory recommended
specifications. If any machining occurred or if replacements were made to the valve guides, the seats
must be machined.
If the seats are in good condition, the valves can be lapped to the seats, and the cylinder head assembled. See
the valves section for instructions on lapping.
If the valve seats are worn, cracked or damaged, they must be serviced by a machine shop. The valve seat
must be perfectly centered to the valve guide, which requires very accurate machining.
CYLINDER HEAD SURFACE
If the cylinder head is warped, it must be machined flat. If the warpage is extremely severe, the head may
need to be replaced. In some instances, it may be possible to straighten a warped head enough to allow
machining. In either case, contact a professional machine shop for service.
Any OHC cylinder head that shows excessive warpage should have the camshaft bearing journals align
bored after the cylinder head has been resurfaced.
WARNING
Failure to align bore the camshaft bearing journals could result in severe engine damage including but not
limited to: valve and piston damage, connecting rod damage, camshaft and/or crankshaft breakage. HOW TO USE THIS BOOK
470 REFINISHING & REPAIRING 
						

							
Certain cracks can be repaired in both cast iron and aluminum heads. For cast iron, a tapered threaded insert is
installed along the length of the crack. Aluminum can also use the tapered inserts, however welding is the
preferred method. Some physical damage can be repaired through brazing or welding. Contact a machine shop
to get expert advice for your particular dilemma.
ASSEMBLY
The first step for any assembly job is to have a clean area in which to work. Next, thoroughly clean all of the
parts and components that are to be assembled. Finally, place all of the components onto a suitable work space
and, if necessary, arrange the parts to their respective positions.
Except the 2.3L, 2.5L and 4.0L SOHC (VIN E) Engines Lightly lubricate the valve stems and insert all of the valves into the cylinder head. If possible,
maintain their original locations.
1. 
If equipped, install any valve spring shims which were removed.
2. 
If equipped, install the new valve seals, keeping the following in mind: If the valve seal presses over the guide, lightly lubricate the outer guide surfaces.
¨ 
If the seal is an O-ring type, it is installed just after compressing the spring but before the
valve locks.
¨ 
3. 
Place the valve spring and retainer over the stem.
4. 
Position the spring compressor tool and compress the spring.
5. 
Assemble the valve locks to the stem.
6. 
Relieve the spring pressure slowly and insure that neither valve lock becomes dislodged by the
retainer.
7. 
Remove the spring compressor tool.
8. 
Repeat Steps 2 through 8 until all of the springs have been installed.
9. 
2.3L, 2.5L and 4.0L SOHC (VIN E) Engines Lightly lubricate the valve stems and insert all of the valves into the cylinder head. If possible,
maintain their original locations.
1. 
If equipped, install any valve spring shims which were removed.
2. 
If equipped, install the new valve seals, keeping the following in mind: If the valve seal presses over the guide, lightly lubricate the outer guide surfaces.
¨ 
If the seal is an O-ring type, it is installed just after compressing the spring but before the
valve locks.
¨ 
3. 
Place the valve spring and retainer over the stem.
4. 
Position the spring compressor tool and compress the spring.
5. 
Assemble the valve locks to the stem.
6. 
Relieve the spring pressure slowly and insure that neither valve lock becomes dislodged by the
retainer.
7. 
Remove the spring compressor tool.
8. 
Repeat Steps 2 through 8 until all of the springs have been installed.
9. 
Install the camshaft(s), rockers, shafts and any other components that were removed for disassembly.
10. 
Engine Block HOW TO USE THIS BOOK
ASSEMBLY 471 
						

							
GENERAL INFORMATION
A thorough overhaul or rebuild of an engine block would include replacing the pistons, rings, bearings, timing
belt/chain assembly and oil pump. For OHV engines also include a new camshaft and lifters. The block would
then have the cylinders bored and honed oversize (or if using removable cylinder sleeves, new sleeves
installed) and the crankshaft would be cut undersize to provide new wearing surfaces and perfect clearances.
However, your particular engine may not have everything worn out. What if only the piston rings have worn
out and the clearances on everything else are still within factory specifications? Well, you could just replace
the rings and put it back together, but this would be a very rare example. Chances are, if one component in
your engine is worn, other components are sure to follow, and soon. At the very least, you should always
replace the rings, bearings and oil pump. This is what is commonly called a freshen up.
Cylinder Ridge Removal
Because the top piston ring does not travel to the very top of the cylinder, a ridge is built up between the end
of the travel and the top of the cylinder bore.
Pushing the piston and connecting rod assembly past the ridge can be difficult, and damage to the piston ring
lands could occur. If the ridge is not removed before installing a new piston or not removed at all, piston ring
breakage and piston damage may occur.
It is always recommended that you remove any cylinder ridges before removing the piston and
connecting rod assemblies. If you know that new pistons are going to be installed and the engine block
will be bored oversize, you may be able to forego this step. However, some ridges may actually prevent
the assemblies from being removed, necessitating its removal.
There are several different types of ridge reamers on the market, none of which are inexpensive. Unless a
great deal of engine rebuilding is anticipated, borrow or rent a reamer.
Turn the crankshaft until the piston is at the bottom of its travel.
1. 
Cover the head of the piston with a rag.
2. 
Follow the tool manufacturers instructions and cut away the ridge, exercising extreme care to avoid
cutting too deeply.
3. 
Remove the ridge reamer, the rag and as many of the cuttings as possible. Continue until all of the
cylinder ridges have been removed.
4. 
DISASSEMBLY
The engine disassembly instructions following assume that you have the engine mounted on an engine stand.
If not, it is easiest to disassemble the engine on a bench or the floor with it resting on the bell housing or
transmission mounting surface. You must be able to access the connecting rod fasteners and turn the
crankshaft during disassembly. Also, all engine covers (timing, front, side, oil pan, whatever) should have
already been removed. Engines which are seized or locked up may not be able to be completely disassembled,
and a core (salvage yard) engine should be purchased.
Except the 2.3L, 2.5L and 4.0L SOHC (VIN E) Engines
If not done during the cylinder head removal, remove the pushrods and lifters, keeping them in order for
assembly. Remove the timing gears and/or timing chain assembly, then remove the oil pump drive assembly
and withdraw the camshaft from the engine block. Remove the oil pick-up and pump assembly. If equipped,
remove any balance or auxiliary shafts. If necessary, remove the cylinder ridge from the top of the bore. See
the cylinder ridge removal procedure earlier in this section. HOW TO USE THIS BOOK
472 GENERAL INFORMATION 
						

							
2.3L, 2.5L and 4.0L SOHC (VIN E) Engines
If not done during the cylinder head removal, remove the timing chain/belt and/or gear/sprocket assembly.
Remove the oil pick-up and pump assembly and, if necessary, the pump drive. If equipped, remove any
balance or auxiliary shafts. If necessary, remove the cylinder ridge from the top of the bore. See the cylinder
ridge removal procedure earlier in this section.
All Engines
Rotate the engine over so that the crankshaft is exposed. Use a number punch or scribe and mark each
connecting rod with its respective cylinder number. The cylinder closest to the front of the engine is always
number 1. However, depending on the engine placement, the front of the engine could either be the flywheel
or damper/pulley end. Generally the front of the engine faces the front of the vehicle. Use a number punch or
scribe and also mark the main bearing caps from front to rear with the front most cap being number 1 (if there
are five caps, mark them 1 through 5, front to rear).
Place rubber hose over the connecting rod studs to protect the crankshaft and cylinder bores from damage
WARNING
Take special care when pushing the connecting rod up from the crankshaft because the sharp threads of the
rod bolts/studs will score the crankshaft journal. Insure that special plastic caps are installed over them, or cut
two pieces of rubber hose to do the same. HOW TO USE THIS BOOK
DISASSEMBLY 473 
						

							Carefully tap the piston out of the bore using a wooden dowel
Again, rotate the engine, this time to position the number one cylinder bore (head surface) up. Turn the
crankshaft until the number one piston is at the bottom of its travel, this should allow the maximum access to
its connecting rod. Remove the number one connecting rods fasteners and cap and place two lengths of rubber
hose over the rod bolts/studs to protect the crankshaft from damage. Using a sturdy wooden dowel and a
hammer, push the connecting rod up about 1 in. (25mm) from the crankshaft and remove the upper bearing
insert. Continue pushing or tapping the connecting rod up until the piston rings are out of the cylinder bore.
Remove the piston and rod by hand, put the upper half of the bearing insert back into the rod, install the cap
with its bearing insert installed, and hand-tighten the cap fasteners. If the parts are kept in order in this
manner, they will not get lost and you will be able to tell which bearings came form what cylinder if any
problems are discovered and diagnosis is necessary. Remove all the other piston assemblies in the same
manner. On V-style engines, remove all of the pistons from one bank, then reposition the engine with the
other cylinder bank head surface up, and remove that banks piston assemblies.
The only remaining component in the engine block should now be the crankshaft. Loosen the main bearing
caps evenly until the fasteners can be turned by hand, then remove them and the caps. Remove the crankshaft
from the engine block. Thoroughly clean all of the components. HOW TO USE THIS BOOK
474 DISASSEMBLY