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17 Repeat this procedure so that the
required bearing shell grade is obtained for
each of the five main bearing journals.
18 Seek the advice of your Peugeot dealer
for the latest information on parts availability
when ordering new bearing shells.
Main bearing running clearance
check
XU series engines
19 On early engines, if the modified bearing
shells are to be fitted, obtain a set of new
(Yellow) upper bearing shells and new Blue
(Class A) lower bearing shells. On later
(mid-1994 on) engines where the modified
bearing shells are already fitted, the running
clearance check can be carried out using the
original bearing shells, although it is
preferable to use a new set, since the results
obtained will be a lot more conclusive.
20 Clean the backs of the bearing shells, and
the bearing locations, in both the cylinder
block/crankcase and the main bearing caps.
21 Press the bearing shells into their locations,
ensuring that the tab on each shell engages in
the notch in the cylinder block/crankcase or
bearing cap, and taking care not to touch any
shell’s bearing surface with your fingers. There
is conflicting information from the manufacturer
on the exact placement of the grooved and
plain bearing shells, which appears to vary
according to engine code and model year.
Also, the bearing arrangement on the project
cars dismantled in the preparation of this
manual did not conform to the expected
placement, but no harm seemed to have
resulted. As a general recommendation, if the
old bearing shells are being used they must be
positioned in their original locations. If new
bearing shells are being used on early models,
fit the plain shells in all locations that had a
plain shell on removal, and likewise for the
grooved shells. From mid-1994 onwards, all
upper bearing shells are grooved, whereas all
lower shells are plain.
22 The running clearance can be checked in
either of two ways.
23 One method (which will be difficult to
achieve without a range of internal
micrometers or internal/external expanding
calipers) is to refit the main bearing caps to
the cylinder block/crankcase, with bearing
shells in place. With the cap retaining bolts
tightened to the specified torque, measure the
internal diameter of each assembled pair of
bearing shells. If the diameter of each
corresponding crankshaft journal is measured
and then subtracted from the bearing internal
diameter, the result will be the main bearing
running clearance.
24 The second (and more accurate) method
is to use a product known as Plastigage. This
consists of a fine thread of perfectly round
plastic, which is then compressed between
the bearing shell and the journal. When the
shell is removed, the plastic is deformed, and
can be measured with a specified card gauge
supplied with the kit. The running clearance is
determined from this gauge. Plastigage
should be available from your Peugeot dealer,
otherwise, enquiries at one of the larger
specialist quality motor factors should
produce the name of a stockist in your area.
The procedure for using Plastigage is as
follows.
25 With the main bearing upper shells in
place, carefully lay the crankshaft in position.
Do not use any lubricant; the crankshaft
journals and bearing shells must be perfectly
clean and dry.
26 Cut several lengths of the
appropriate-size Plastigage (they should be
slightly shorter than the width of the main
bearings), and place one length on each
crankshaft journal axis (see illustration).
27 With the main bearing lower shells in
position, refit the main bearing caps and
tighten their retaining bolts to the specified
torque. Take care not to disturb the
Plastigage, and do not rotate the crankshaft at
any time during this operation.
28 Remove the main bearing caps again,
taking great care not to disturb the Plastigage,
nor to rotate the crankshaft.
29 Compare the width of the crushed
Plastigage on each journal to the scale printed
on the Plastigage envelope, to obtain the main
bearing running clearance (see illustration).
Compare the clearance measured with that
given in the Specifications at the start of this
Chapter.
30 If the clearance is significantly different
from that expected, the bearing shells may be
the wrong size (or excessively worn, if the
original shells are being re-used). Before
deciding that different size shells are required,
make sure that no dirt or oil was trapped
between the bearing shells and the caps or
block when the clearance was measured. If
the Plastigage was wider at one end than at
the other, the crankshaft journal may be
tapered.
31 If the clearance is not as specified, use
the reading obtained, along with the shell
thicknesses quoted above, to calculate the
necessary grade of bearing shells required.
When calculating the bearing clearance
required, bear in mind that it is always better
to have the running clearance towards the
lower end of the specified range, to allow for
wear in use.
32 Where necessary, obtain the required
grades of bearing shell, and repeat the
running clearance checking procedure as
described above.
33 On completion, carefully scrape away all
traces of the Plastigage material from the
crankshaft and bearing shells, using a
fingernail or other object which is unlikely to
score the bearing surfaces.
TU series aluminium block engines
34 The procedure is similar to that described
in paragraphs 20 to 33, except that the lower
shells are fitted to the main bearing ladder
instead of the individual bearing caps. On early
engines, if the modified bearing shells are to
Engine removal and overhaul procedures 2D•19
2D
13.26 Plastigage in place on a crankshaft main bearing journal 13.29 Measure the width of the deformed Plastigage using the
scale on the card