Ford Mondeo (petrol engines). Manual - part 21

Note: Always check first what replacement
parts are available before planning any
overhaul operation; refer to Section 1 of this
Part. A Ford dealer, or a good engine
reconditioning specialist/automotive parts
supplier may be able to suggest alternatives
which will enable you to overcome the lack of
replacement parts.
1 Before the inspection process can be
carried out, the piston/connecting rod
assemblies must be cleaned, and the original
piston rings removed from the pistons. The
rings should have smooth, polished working
surfaces, with no dull or carbon-coated
sections (showing that the ring is not sealing
correctly against the bore wall, so allowing
combustion gases to blow by) and no traces
of wear on their top and bottom surfaces. The
end gaps should be clear of carbon, but not
polished (indicating a too-small end gap), and
all the rings (including the elements of the oil
control ring) should be free to rotate in their
grooves, but without excessive up-and-down
movement. If the rings appear to be in good
condition, they are probably fit for further use;
check the end gaps (in an unworn part of the
bore) as described in Section 16. If any of the
rings appears to be worn or damaged, or has
an end gap significantly different from the
specified value, the usual course of action is
to renew all of them as a set. Note: While it is
usual always to renew piston rings when an
engine is overhauled, this of course assumes
that rings are available separately - if not, it
follows that great care must be taken not to
break or damage any of the rings during the
following procedures, and to ensure that each
ring is marked on removal so that it is refitted
only the original way up, and only to the same
groove.
2 Using a piston ring renoval tool, carefully
remove the rings from the pistons. Be careful
not to nick or gouge the pistons in the
process, and mark or label each ring as it is
removed, so that its original top surface can

be identified on reassembly, and so that it can
be returned to its original groove. Take care
also with your hands - piston rings are sharp!
3 Scrape all traces of carbon from the top of
the piston. A hand-held wire brush or a piece
of fine emery cloth can be used, once the
majority of the deposits have been scraped
away. Do not, under any circumstances, use a
wire brush mounted in a drill motor to remove
deposits from the pistons - the piston material
is soft, and may be eroded away by the wire
brush.
4 Use a piston ring groove-cleaning tool to
remove carbon deposits from the ring
grooves. If a tool isn’t available, but
replacement rings have been found, a piece
broken off the old ring will do the job. Be very
careful to remove only the carbon deposits -
don’t remove any metal, and do not nick or
scratch the sides of the ring grooves (see
illustrations). Protect your fingers - piston
rings are sharp!
5 Once the deposits have been removed,
clean the piston/rod assemblies with solvent,
and dry them with compressed air (if
available). Make sure the oil return holes in the
back sides of the ring grooves, and the oil

hole in the lower end of each rod, are clear.
6 If the pistons and cylinder walls aren’t
damaged or worn excessively - refer to
Section 11 for details of inspection and
measurement procedures - and if the cylinder
block/crankcase is not rebored, new pistons
won’t be necessary. Normal piston wear
appears as even vertical wear on the piston
thrust surfaces, and slight looseness of the
top ring in its groove.
7 Carefully inspect each piston for cracks
around the skirt, at the pin bosses, and at the
ring lands (between the ring grooves).
8 Look for scoring and scuffing on the thrust
faces of the skirt, holes in the piston crown,
and burned areas at the edge of the crown. If
the skirt is scored or scuffed, the engine may
have been suffering from overheating and/or
abnormal combustion, which caused
excessively-high operating temperatures. The
cooling and lubrication systems should be
checked thoroughly. A hole in the piston
crown is an indication that abnormal
combustion (pre-ignition) was occurring.
Burned areas at the edge of the piston crown
are usually evidence of spark knock
(detonation). If any of the above problems
exist, the causes must be corrected, or the
damage will occur again. The causes may
include intake air leaks, incorrect fuel/air
mixture, incorrect ignition timing, or EGR
system malfunctions.
9 Corrosion of the piston, in the form of small
pits, indicates that coolant is leaking into the
combustion chamber and/or the crankcase.
Again, the cause must be corrected, or the
problem may persist in the rebuilt engine.
10 Check the piston-to-rod clearance by
twisting the piston and rod in opposite
directions. Any noticeable play indicates
excessive wear, which must be corrected. The
piston/connecting rod assemblies should be
taken to a Ford dealer or engine recondition-
ing specialist to have the pistons, gudgeon
pins and rods checked, and new components
fitted as required.
11 Don’t attempt to separate the pistons
from the connecting rods (even if non-genuine
replacements are found elsewhere). This is a
task for a Ford dealer or similar engine
reconditioning specialist, due to the special
heating equipment, press, mandrels and
supports required to do the job. If the
piston/connecting rod assemblies do require
this sort of work, have the connecting rods
checked for bend and twist, since only such
engine repair specialists will have the facilities
for this purpose.
12 Check the connecting rods for cracks and
other damage. Temporarily remove the big-
end bearing caps and the old bearing shells,
wipe clean the rod and cap bearing recesses,
and inspect them for nicks, gouges and
scratches. After checking the rods, replace
the old shells, slip the caps into place, and
tighten the bolts finger-tight.

12 Piston/connecting rod

assemblies - inspection

Engine removal and general engine overhaul procedures 2B•17

12.4A The piston ring grooves can be

cleaned with a special tool, as shown

here . . .

12.4B . . . or a section of a broken ring, if

available

If a piston ring removal tool is not
available, the rings can be removed by
hand, expanding them over the top of
the pistons. The use of two or three old
feeler blades will be helpful in
preventing the rings dropping into
empty grooves.

Warning: Wear eye protection
when using compressed air! Be
sure to clean the oil holes with a
pipe cleaner or similar probe.

2 Check the main and crankpin (big-end)
bearing journals for uneven wear, scoring,
pitting and cracking.
3 Rub a penny across each journal several
times (see illustration). If a journal picks up
copper from the penny, it is too rough.
4 Remove all burrs from the crankshaft oil
holes with a stone, file or scraper.
5 Using a micrometer, measure the diameter
of the main bearing and crankpin (big-end)
journals, and compare the results with the
Specifications at the beginning of this Chapter
(see illustration).
6 By measuring the diameter at a number of
points around each journal’s circumference,
you will be able to determine whether or not
the journal is out-of-round. Take the
measurement at each end of the journal, near
the webs, to determine if the journal is
tapered.
7 If the crankshaft journals are damaged,
tapered, out-of-round, or worn beyond the
limits specified in this Chapter, the crankshaft
must be taken to an engine overhaul
specialist, who will regrind it, and who can
supply the necessary undersize bearing
shells.
8 Check the oil seal journals at each end of
the crankshaft for wear and damage. If either
seal has worn an excessive groove in its

journal, consult an engine overhaul specialist,
who will be able to advise whether a repair is
possible, or whether a new crankshaft is
necessary.

Note: Always check first what replacement
parts are available before planning any
overhaul operation; refer to Section 1 of this
Part. A Ford dealer, or a good engine
reconditioning specialist/automotive parts
supplier, may be able to suggest alternatives
which will enable you to overcome the lack of
replacement parts.
1 Even though the main and big-end bearing
shells should be renewed during the engine
overhaul, the old shells should be retained for
close examination, as they may reveal
valuable information about the condition of
the engine (see illustration).
2 Bearing failure occurs because of lack of
lubrication, the presence of dirt or other
foreign particles, overloading the engine, and
corrosion. Regardless of the cause of bearing
failure, it must be corrected before the engine
is reassembled, to prevent it from happening
again.
3 When examining the bearing shells, remove
them from the cylinder block/crankcase and
main bearing caps, and from the connecting
rods and the big-end bearing caps, then lay
them out on a clean surface in the same
general position as their location in the
engine. This will enable you to match any
bearing problems with the corresponding
crankshaft journal. Do not touch any shell’s
bearing surface with your fingers while
checking it, or the delicate surface may be
scratched.
4 Dirt or other foreign matter gets into the
engine in a variety of ways. It may be left in
the engine during assembly, or it may pass
through filters or the crankcase ventilation
system. It may get into the oil, and from there
into the bearings. Metal chips from machining
operations and normal engine wear are often
present. Abrasives are sometimes left in
engine components after reconditioning,

especially when parts are not thoroughly
cleaned using the proper cleaning methods.
Whatever the source, these foreign objects
often end up embedded in the soft bearing
material, and are easily recognized. Large
particles will not embed in the material, and
will score or gouge the shell and journal. The
best prevention for this cause of bearing
failure is to clean all parts thoroughly, and to
keep everything spotlessly-clean during
engine assembly. Frequent and regular engine
oil and filter changes are also recommended.
5 Lack of lubrication (or lubrication
breakdown) has a number of inter-related
causes. Excessive heat (which thins the oil),
overloading (which squeezes the oil from the
bearing face) and oil leakage (from excessive
bearing clearances, worn oil pump or high
engine speeds) all contribute to lubrication
breakdown. Blocked oil passages, which
usually are the result of misaligned oil holes in
a bearing shell, will also starve a bearing of oil,
and destroy it. When lack of lubrication is the
cause of bearing failure, the bearing material
is wiped or extruded from the shell’s steel
backing. Temperatures may increase to the
point where the steel backing turns blue from
overheating.
6 Driving habits can have a definite effect on
bearing life. Full-throttle, low-speed operation
(labouring the engine) puts very high loads on
bearings, which tends to squeeze out the oil
film. These loads cause the shells to flex,
which produces fine cracks in the bearing
face (fatigue failure). Eventually, the bearing
material will loosen in pieces, and tear away
from the steel backing. Short-distance driving
leads to corrosion of bearings, because
insufficient engine heat is produced to drive
off condensed water and corrosive gases.
These products collect in the engine oil,
forming acid and sludge. As the oil is carried

14 Main and big-end bearings -

inspection

13 Crankshaft - inspection

2B•18 Engine removal and general engine overhaul procedures

13.3 Rubbing a penny lengthwise along

each journal will reveal its condition - if

copper rubs off and is embedded in the

crankshaft, the journals should be

reground

13.5 Measure the diameter of each

crankshaft journal at several points, to

detect taper and out-of-round conditions

14.1 When inspecting the main and big-

end bearings, look for these problems

to the engine bearings, the acid attacks and
corrodes the bearing material.
7 Incorrect shell refitting during engine
assembly will lead to bearing failure as well.
Tight-fitting shells leave insufficient bearing
running clearance, and will result in oil
starvation. Dirt or foreign particles trapped
behind a bearing shell result in high spots on
the bearing, which lead to failure. Do not
touch any shell’s bearing surface with your
fingers during reassembly; there is a risk of
scratching the delicate surface, or of
depositing particles of dirt on it.

1 Before reassembly begins, ensure that all
new parts have been obtained, and that all
necessary tools are available. Read through
the entire procedure, to familiarise yourself
with the work involved, and to ensure that all
items necessary for reassembly of the engine
are at hand. In addition to all normal tools and
materials, suitable sealant will be required for
two of the joint faces (Ford recommend
Hylosil 102 for the cylinder block/crankcase-
to-sump/oil pump/oil seal carrier joints, and
Loctite 518 for the camshaft right-hand
bearing caps). In all other cases, provided the
relevant mating surfaces are clean and flat,
new gaskets will be sufficient to ensure joints
are oil-tight. Do not use any kind of silicone-
based sealant on any part of the fuel system
or inlet manifold, and never use exhaust
sealants upstream of the catalytic converter.
2 In order to save time and avoid problems,
engine reassembly can be carried out in the
following order:
(a) Crankshaft (Section 17).
(b) Piston/connecting rod assemblies

(Section 18).

(c) Oil pump (Part A of this Chapter, Section

16).

(d) Sump (Part A of this Chapter, Section 15).
(e) Flywheel/driveplate (Part A of this

Chapter, Section 21).

(f)

Cylinder head (Part A of this Chapter,
Section 14).

(g) Timing belt inner cover, tensioner and

toothed pulleys, and timing belt (Part A of
this Chapter).

(h) Engine external components.
3 At this stage, all engine components should
be absolutely clean and dry, with all faults
repaired; they should be laid out (or in
individual containers) on a completely-clean
work surface.

1 Before installing new piston rings, check
the end gaps. Lay out each piston set with a
piston/connecting rod assembly, and keep
them together as a matched set from now on.
2 Insert the top compression ring into the first
cylinder, and square it up with the cylinder
walls by pushing it in with the top of the piston
(see illustration). The ring should be near the
bottom of the cylinder, at the lower limit of
ring travel.
3 To measure the end gap, slip feeler gauges
between the ends of the ring, until a gauge
equal to the gap width is found (see
illustration). The feeler gauge should slide
between the ring ends with a slight amount of
drag. Compare the measurement to the value
given in the Specifications Section of this
Chapter; if the gap is larger or smaller than
specified, double-check to make sure you
have the correct rings before proceeding. If
you are assessing the condition of used rings,
have the cylinder bores checked and
measured by a Ford dealer or similar engine
reconditioning specialist, so that you can be
sure of exactly which component is worn, and
seek advice as to the best course of action to
take.
4 If the end gap is still too small, it must be
opened up by careful filing of the ring ends
using a fine file. If it is too large, this is not as
serious, unless the specified limit is exceeded,
in which case very careful checking is
required of the dimensions of all components,
as well as of the new parts.
5 Repeat the procedure for each ring that will
be installed in the first cylinder, and for each

ring in the remaining cylinders. Remember to
keep rings, pistons and cylinders matched up.
6 Refit the piston rings as follows. Where the
original rings are being refitted, use the marks
or notes made on removal, to ensure that
each ring is refitted to its original groove and
the same way up. New rings generally have
their top surfaces identified by markings
(often an indication of size, such as “STD”, or
the word “TOP”) - the rings must be fitted with
such markings uppermost (see illustration).
Note: Always follow the manuals printed
on the ring package or box - different
manufacturers may require different
approaches. Do not mix up the top and
second compression rings, as they usually
have different cross-sections.
7 The oil control ring (lowest one on the
piston) is usually installed first. It is composed
of three separate elements. Slip the
spacer/expander into the groove (see
illustration). If an anti-rotation tang is used,
make sure it is inserted into the drilled hole in
the ring groove. Next, install the lower side
rail. Don’t use a piston ring installation tool on
the oil ring side rails, as they may be
damaged. Instead, place one end of the side
rail into the groove between the
spacer/expander and the ring land, hold it
firmly in place, and slide a finger around the
piston while pushing the rail into the groove

16 Piston rings - refitting

15 Engine overhaul -

reassembly sequence

Engine removal and general engine overhaul procedures 2B•19

16.7A Installing the spacer/expander in

the oil control ring groove

16.2 When checking piston ring end gap,

the ring must be square in the cylinder

bore (this is done by pushing the ring down

with the top of a piston, as shown)

16.3 With the ring square in the bore,

measure the end gap with a feeler

gauge

16.6 Look for etched markings (“STD” -

indicating a standard-sized ring - shown

here) identifying piston ring top surface

(see illustration). Next, install the upper side
rail in the same manner.
8 After the three oil ring components have
been installed, check that both the upper and
lower side rails can be turned smoothly in the
ring groove.
9 The second compression (middle) ring is
installed next, followed by the top
compression ring - ensure their marks are
uppermost, and be careful not to confuse
them. Don’t expand either ring any more than
necessary to slide it over the top of the piston.
10 With all the rings in position, space the
ring gaps (including the elements of the oil
control ring) uniformly around the piston at
120° intervals. Repeat the procedure for the
remaining pistons and rings.

1 Crankshaft refitting is the first major step in
engine reassembly. It is assumed at this point
that the cylinder block/crankcase and
crankshaft have been cleaned, inspected and
repaired or reconditioned as necessary.
Position the engine upside-down.
2 Remove the main bearing cap bolts, and lift

out the caps. Lay the caps out in the proper
order, to ensure correct installation.
3 If they’re still in place, remove the old
bearing shells from the block and the main
bearing caps. Wipe the bearing recesses of
the block and caps with a clean, lint-free
cloth. They must be kept spotlessly-clean!

Main bearing running clearance
check

4 Clean the backs of the new main bearing
shells. Fit the shells with an oil groove in each
main bearing location in the block; note the
thrustwashers integral with the No 3 (centre)
main bearing upper shell. Fit the other shell
from each bearing set in the corresponding
main bearing cap. Make sure the tab on each
bearing shell fits into the notch in the block or
cap. Also, the oil holes in the block must line
up with the oil holes in the bearing shell (see
illustration).

Caution: Don’t hammer the shells
into place, and don’t nick or gouge
the bearing faces. No lubrication
should be used at this time.

5 Clean the bearing surfaces of the shells in

the block and the crankshaft main bearing
journals with a clean, lint-free cloth. Check or
clean the oil holes in the crankshaft, as any
dirt here can go only one way - straight
through the new bearings.
6 Once you’re certain the crankshaft is clean,
carefully lay it in position in the main bearings.
Trim several pieces of the appropriate-size
Plastigage (they must be slightly shorter than
the width of the main bearings), and place one
piece on each crankshaft main bearing
journal, parallel with the crankshaft centre-line
(see illustration).
7 Clean the bearing surfaces of the cap
shells, and install the caps in their respective
positions (don’t mix them up) with the arrows
pointing to the timing belt end of the engine.
Don’t disturb the Plastigage (see illustration).
8 Working on one cap at a time, from the
centre main bearing outwards (and ensuring
that each cap is tightened down squarely and
evenly onto the block), tighten the main
bearing cap bolts to the specified torque
wrench setting. Don’t rotate the crankshaft at
any time during this operation!
9 Remove the bolts, and carefully lift off the
main bearing caps. Keep them in order. Don’t
disturb the Plastigage or rotate the
crankshaft. If any of the main bearing caps are
difficult to remove, tap them gently from side-
to-side with a soft-faced mallet to loosen
them.
10 Compare the width of the crushed
Plastigage on each journal with the scale
printed on the Plastigage envelope to obtain
the main bearing running clearance (see
illustration). Check the Specifications to
make sure that the clearance is correct.
11 If the clearance is not as specified, seek
the advice of a Ford dealer or similar engine
reconditioning specialist - if the crankshaft
journals are in good condition (see Sec-
tion 13), it may be possible simply to renew
the shells to achieve the correct clearance. If
this is not possible, the crankshaft must be
reground by a specialist who can supply the
necessary undersized shells. First though,

17 Crankshaft -

refitting and main bearing
running clearance check

2B•20 Engine removal and general engine overhaul procedures

16.7B DO NOT use a piston ring

installation tool when installing the oil ring

side rails

17.4 Tab on each bearing shell must

engage with notch in block or cap, and oil

holes in upper shells must align with block

oilways

17.6 Lay the Plastigage strips (arrowed) on

the main bearing journals, parallel to the

crankshaft centre-line

17.7 Refit the main bearing caps and

tighten the bolts as specified

17.10 Compare the width of the crushed

Plastigage to the scale on the envelope to

determine the main bearing oil clearance

(always take the measurement at the

widest point of the Plastigage). Be sure to
use the correct scale; Imperial and metric

scales are included

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