Using A Feeler Blade To Remove A Piston Ring - Opel Zafira B MPV 2006 Owners Workshop Manual

clear. Dry the block and, where necessary, the
lower casing thoroughly and wipe all machined
surfaces with a light oil. If you have access to
compressed air, use it to speed-up the drying
process, and to blow out all the oil holes and
galleries.
A.
Warning: Wear eye protection
.£ll.
when using compressed air.
6 If the block and lower casing are relatively
clean, an adequate cleaning job can be
achieved with hot soapy water and a stiff
brush. Take plenty of time, and do a thorough
job. Regardless of the cleaning method used,
be sure to clean all oil holes and galleries very
thoroughly, dry everything completely, and
coat all cast-iron machined surfaces with light
oil.
7 The threaded holes in the cylinder block must
be clean, to ensure accurate torque readings
when tightening fixings during reassembly. Run
the correct-size tap (which can be determined
from the size of the relevant bolt} into each of
the holes to remove rust, corrosion, thread
sealant or other contamination, and to restore
damaged threads. If possible, use compressed
air to clear the holes of debris produced by this
operation. Do not forget to clean the threads of
all bolts and nuts which are to be re-used, as
well.
8 Where applicable, apply suitable sealant
to the new oil gallery plugs, and insert them
into the relevant holes in the cylinder block.
Tighten the plugs securely. On diesel engines,
refit the oil spray nozzles into the block and
secure with the retaining bolts tightened
securely.
9 If the engine is to be left dismantled for
some time, cover the cylinder block with a
large plastic bag to keep it clean and prevent
corrosion. Where applicable, refit the lower
casing and tighten the bolts finger-tight.
Inspection
10 Visually check the block for cracks, rust
and corrosion. Look for stripped threads in the
threaded holes. It's also a good idea to have
the block checked for hidden cracks by an
engine reconditioning specialist that has the
equipment to do this type of work, especially
if the vehicle had a history of overheating or
using coolant. If defects are found, have the
block repaired, if possible, or renewed.
11 If in any doubt as to the condition of the
cylinder block, have it inspected and measured
by an engine reconditioning specialist. If the
bores are worn or damaged, they will be able
to carry out any necessary reboring (where
possible}, and supply appropriate oversized
pistons, etc.
1 Before the inspection process can begin,
the piston/connecting rod assemblies must be
Engine removal and overhaul procedures 2E•13
cleaned, and the original piston rings removed
from the pistons. Note: Always use new piston
rings when the engine is reassembled.
2 Carefully expand the old rings over the top
of the pistons. The use of two or three old
feeler gauges will be helpful in preventing
the rings dropping into empty grooves (see
illustration). Take care, however, as piston
rings are sharp.
3 Scrape away 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.
4 Remove the carbon from the ring grooves
in the piston, using an old ring. Break the ring
in half to do this (be careful not to cut your
fingers - piston rings are sharp}. Be very
careful to remove only the carbon deposits -
do not remove any metal, and do not nick or
scratch the sides of the ring grooves.
5 Once the deposits have been removed,
clean the piston/connecting rod assembly
with paraffin or a suitable solvent, and dry
thoroughly. Make sure that the oil return holes
in the ring grooves are clear.
6 If the pistons and cylinder bores are not
damaged or worn excessively, and if the
cylinder block does not need to be rebored,
the original pistons can be refitted. Normal
piston wear shows up as even vertical wear
on the piston thrust surfaces, and slight
looseness of the top ring in its groove. New
piston rings should always be used when the
engine is reassembled.
7 Carefully inspect each piston for cracks
around the skirt, at the gudgeon pin bosses,
and at the piston ring lands (between the ring
grooves}.
8 Look for scoring and scuffing on the thrust
faces of the piston 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
('pinking') which caused excessively-high
operating temperatures. The cooling and
lubrication systems should be checked
thoroughly. A hole in the piston crown, or
burned areas at the edge of the piston crown
indicates that abnormal combustion (pre-
ignition, 'pinking', knocking or detonation) has
been occurring. If any of the above problems
exist, the causes must be investigated and
corrected, or the damage will occur again.
9 Corrosion of the piston, in the form of
pitting, indicates that coolant has been
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 If in any doubt as to the condition of
the pistons and connecting rods, have
them inspected and measured by an engine
reconditioning specialist. If new parts are
required, they will be able to supply and fit
appropriate-sized pistons/rings, and rebore
(where possible) or hone the cylinder block.
12.2
Using a feeler blade to remove a
piston ring
1 Clean the crankshaft using paraffin or a
suitable solvent, and dry it, preferably with
compressed air if available. Be sure to clean
the oil holes with a pipe cleaner or similar
probe, to ensure that they are not obstructed.
A
Warning: Wear eye protection
.£ll.
when using compressed air.
2 Check the main and big-end bearing
journals for uneven wear, scoring, pitting and
cracking.
3 Big-end bearing wear is accompanied by
distinct metallic knocking when the engine
is running (particularly noticeable when the
engine is pulling from low revs), and some
loss of oil pressure.
4 Main bearing wear is accompanied by
severe engine vibration and rumble - getting
progressively worse as engine revs increase -
and again by loss of oil pressure.
5 Check the bearing journal for roughness by
running a finger lightly over the bearing surface.
Any roughness (which will be accompanied
by obvious bearing wear) indicates that the
crankshaft requires regrinding.
6 If the crankshaft has been reground, check
for burrs around the crankshaft oil holes (the
holes are usually chamfered, so burrs should
not be a problem unless regrinding has been
carried out carelessly). Remove any burrs with
a fine file or scraper, and thoroughly clean the
oil holes as described previously.
7 Have the crankshaft journals measured
by an engine reconditioning specialist. If the
crankshaft is worn or damaged, they may be
able to regrind the journals and supply suitable
undersize bearing shells. If no undersize shells
are available and the crankshaft has worn
beyond the specified limits, it will have to be
renewed. Consult your Vauxhall/Opel dealer
or engine reconditioning specialist for further
information on parts availability.
8 If a new crankshaft is to be fitted, undo
the screws securing the crankshaft speed/
position sensor pulse pick-up ring to the
crankshaft, and transfer the ring to the new
crankshaft.