1983 FIAT UNO belt

8Turn the crankshaft sprocket bolt, or
engage top gear and raise and turn a front
roadwheel, until the camshaft sprocket TDC
timing mark is aligned with the mark on the
cylinder head and the crankshaft sprocket
timing mark is aligned with the mark on the oil
pump cover (photos).
9Release the nut on the timing belt
tensioner, move the pulley away from the belt
and retighten the nut to hold the pulley in the
retracted position (photo).
10Slide the drivebelt from the sprockets.
11When refitting the new belt, make sure
that the sprocket timing marks are still in
alignment and fit the belt so that the arrows
on the belt point in the direction of engine
rotation, and the lines of the belt coincide with
the sprocket marks.
12Engage the timing belt with the crankshaft
sprocket first, then place it around the coolant
pump sprocket and the camshaft sprocket
(photo). Finally slip the belt around the
tensioner pulley.
13Release the tensioner nut and push the
pulley against the belt until the belt is quite
taut. Check that the sprocket timing marks
have not moved out of alignment. If they have,
reset them by moving them over the belt
teeth.
14Still applying force to the pulley, tighten its
nut.
15Turn the crankshaft through two complete
turns in the normal direction of rotation and
check that when the centre of the longest runof the belt is gripped between finger and
thumb it can just be twisted through 90º. If
increased tension is required to achieve this,
release the tensioner nut and prise the pulley
against the timing belt. Note: The above
procedure serves only as a rough guide to
setting the belt tension having it checked by a
FIAT dealer at the earliest opportunity is
recommended.
16Refit the timing belt cover, the crankshaft
pulley, alternator drivebelt, spark plugs and
the air cleaner.
Camshaft -
removal and refitting#
Warning: Refer to the beginning
of Section 9 before starting any
work.
17Remove the air cleaner and the fuel pump(carb. models), as described in Section 9 of
this Supplement.
18Remove the distributor (Section 10).
19Remove the timing belt cover.
20Unbolt and remove the camshaft cover,
having first disconnected the HT lead clip
(photos).
21Turn the crankshaft (by engaging top gear
and raising and turning a front roadwheel)
until No. 4 piston is at TDC. The timing mark
on the camshaft sprocket will be in alignment
with the mark on the cylinder head.
22Pass a rod through one of the holes in the
camshaft sprocket to prevent it rotating and
then unscrew the sprocket fixing bolt. Slip the
sprocket from the camshaft and out of the
loop of the belt (photos).
23Mark the camshaft bearing caps as to
position and then unbolt and remove the
Supplement: Revisions and information on later models 13•21
5B.9 Releasing the timing belt tensioner
nut5B.8B Crankshaft sprocket timing mark
and oil pump cover alignment mark
(arrowed)5B.8A Camshaft sprocket timing mark and
cylinder head timing mark in alignment
5B.22B Camshaft sprocket bolt and
washer5B.22A Unscrewing the camshaft sprocket
bolt
5B.20A Camshaft cover HT lead clip5B.12 Fitting the timing belt
5B.20B Removing the camshaft cover
13

lubrication pipe (prise the oil feed stub out
with a screwdriver), unscrew the remaining
bolts and take off the bearing caps (photos).
24Lift the camshaft carefully from the
cylinder head, checking that the valve
clearance shims and cam followers are not
withdrawn by the adhesion of the oil (photo).
25If the shims and cam followers are to be
removed, keep them in their originally fitted
order (photos).
26Refitting is a reversal of removal but use a
new camshaft oil seal and camshaft cover
gasket. Oil the camshaft bearings (photos).
27Make sure that the timing belt is
reconnected and tensioned as described
previously.
28Check the valve clearances.
29Tighten all nuts and bolts to the specified
torque.
Cylinder head -
removal and refitting#
Warning: Refer to the beginning
of Section 9 before starting any
work.
Note: The cylinder head should be removed
cold.
30Drain the cooling system.
31Remove the air cleaner.
32Disconnect the throttle and choke
connections from the carburettor (photo).
33On carburettor models, disconnect the
fuel hoses from the fuel pump and the
carburettor. On fuel injection models,
13•22 Supplement: Revisions and information on later models
5B.26B Camshaft cover gasket5B.26A Camshaft oil seal5B.25B Removing a cam follower (tappet)
with shim
2B.25A Valve clearance shim showing
thickness mark5B.24 Removing the camshaft
5B.23D Camshaft bearing cap showing
short and long positioning dowels for
correct fitting5B.23C Camshaft lubrication pipe
5B.23B Unscrewing the camshaft
bearing/banjo union bolt5B.23A Prising out the camshaft oil feed
pipe stub5B.22C Camshaft sprocket showing
integral key (arrowed)

depressurize the fuel system, before
disconnecting the fuel pipes and removing the
throttle body, as described in Section 9D.
34Disconnect the coolant and vacuum
hoses from the cylinder head and inlet
manifold (photo).
35Disconnect the electrical lead from the
coolant temperature switch, the LT leads from
the distributor and the idle cut-off solenoid
lead.
36Remove the distributor cap, disconnect
the plug leads and place the cap and leads to
one side of the engine compartment.
37Unbolt and remove the timing belt cover.
38Set No. 4 piston to TDC and then release
the timing belt tensioner and slip the belt from
the camshaft and coolant pump sprockets.
39Unbolt and remove the inlet manifold,
complete with carburettor, or throttle body as
applicable.
40Unbolt the exhaust manifold from the
cylinder head and tie it to one side of the
engine compartment; the downpipe bracket
will have to be disconnected.
41Unscrew the cylinder head bolts, a half
turn at a time in the reverse order to that
shown in Fig. 1.30 of Chapter 1. When the
bolts are free, remove them with their
washers.
42Lift the cylinder head from the block. If it is
stuck tight, insert pieces of wood into the
exhaust or inlet ports and use them as levers
to “rock” the head off the block. On no
account drive levers into the gasket joint orattempt to tap the head sideways as it is
located on positioning dowels.
43Remove and discard the cylinder head
gasket and both manifold gaskets.
44The cylinder head can be dismantled after
removing the camshaft and cam followers as
described in the preceding sub-Section.
45Further dismantling and decarbonising are
described in Chapter 1, Section 39. Note that
single valve springs are used.
46If the valves have been ground in, the
valve clearances will require adjusting, as
described previously. This should be done
before the cylinder head is refitted to the
engine.
47Before refitting the assembled cylinder
head, make sure that the head and block
mating surfaces are perfectly clean, and that
the block bolt holes have been cleared of any
oil.
48The camshaft sprocket timing mark must
be aligned with the one on the cylinder head.
49The new gasket should not be removed
from its nylon cover until required for use. Fit
the gasket dry to perfectly clean surfaces.
50Place the gasket on the cylinder block so
that the word ALTO can be read from above
(photos).
51Lower the cylinder head onto the block so
that it locates on the positioning dowels
(photo).
52The cylinder head bolts must have clean
threads, dipped in engine oil and allowed to
drain for thirty minutes. Screw the bolts infinger-tight and then tighten them in the
sequence shown in Fig. 1.30 of Chapter 1,
and in the stages specified (see Specification)
(photos).
53Refit the inlet manifold and carburettor
using a new gasket.
54Reconnect the exhaust manifold using a
new gasket. Tighten all nuts to the specified
torque. Reconnect the exhaust downpipe
bracket.
55Reconnect the timing belt and tension it
as described earlier.
56Refit the timing belt cover and the
distributor cap and camshaft cover.
57Reconnect all hoses, electrical leads and
controls.
58Fit the air cleaner.
59Fill and bleed the cooling system.
Supplement: Revisions and information on later models 13•23
5B.50A Cylinder head gasket5B.34 Inlet manifold coolant hose (A) and
brake servo vacuum hose (B)5B.32 Disconnecting the throttle cable
5B.52B Typical disc for angular tightening
of cylinder head bolts
5B.50B Cylinder head gasket top surface
marking
5B.52A Inserting a cylinder head bolt5B.51 Fitting the cylinder head
13

Sump pan -
removal and refitting Á
60Drain the engine oil.
61Unbolt and remove the cover plate from
the lower part of the flywheel housing (photo).
The two lower bolts retain the gearchange rod
support strut.
62Unscrew the sump pan securing screws
and pull the sump pan downwards to remove
it (photo). The joint sealant will require cutting
with a sharp knife to release the pan. Clean
away all old gasket material.
63A bead 3.0 mm in diameter of RTV
silicone instant gasket should be applied to
the sump pan flange and then the pan offered
up. Screw in the fixing screws and tighten to
the specified torque. Note the flange end
fixing screw nuts (photos).64Wait one hour before filling with engine oil.
65Refit the flywheel housing cover plate.Oil pump - removal,
checking and refitting#
66Drain the engine oil and remove the sump
pan as described in the last sub-Section.
Unscrew and remove the oil filter cartridge.
67Remove the timing belt.
68Lock the crankshaft against rotation either
by placing a block of wood between a
crankshaft web and the inside of the
crankcase or by jamming the flywheel starter
ring gear with a suitable tool.
69Unscrew and remove the crankshaft
sprocket bolt and take off the timing belt
sprocket. If it is tight, use two screwdrivers to
lever it off or use a two- or three-legged puller.
70Unbolt and remove the oil pick-up/filter
screen assembly. Note the sealing washer.71Extract the oil pump fixing bolts and
withdraw the pump.
72The oil pump incorporates a pressure
relief valve which can be removed for
examination by depressing the spring plunger
and pulling out the keeper plate (photos).
73If pump wear is suspected, check the
gears in the following way. Extract the fixing
screws and remove the rear cover plate. The
screws are very tight and will probably require
the use of an impact driver to release them
(photo).
74Check the clearance between the outer
gear and the pump housing using feeler
blades, and also the gear endfloat by placing
a straight-edge across the pump body and
checking the gap between the straight-edge
and gear face. If the clearances are outside
the specified tolerance, renew the oil pump
complete (photos).
13•24 Supplement: Revisions and information on later models
5B.74B Checking the oil pump gear
endfloat5B.74A Checking the oil pump gear-to-
housing clearance5B.73 Removing the oil pump rear cover
plate screws
5B.72B Oil pump relief valve components5B.72A Removing the oil pump relief valve
keeper plate5B.63B Sump pan flange end fixing screw
and nut
5B.63A Tightening a sump pan screw5B.62 Removing the sump pan5B.61 Removing the flywheel housing
cover plate

75If the pump is unworn, refit the rear cover
plate and tighten the screws fully.
76Apply air pressure from a tyre pump to the
oil pump oil ducts to clear any sludge or other
material and then prime the pump by pouring
clean engine oil into its intake duct at the
same time turning the oil pump inner gear with
the fingers.
77Lever out the oil seal and drive a new one
squarely into the oil pump casing (photos).
Lubricate the oil seal lips.
78Bolt the pump into position using a new
joint gasket. Note one bolt is longer than the
others (photo).
79Bolt on the oil pick-up assembly using a
new sealing washer.
80Fit the crankshaft sprocket and tighten the
bolt to specified torque.
81Fit and tension the timing belt.
82Fit the sump pan. Screw on a new oil filter
cartridge. Wait for the specified period of time
(one hour) and then fill the engine with oil.
83Run the engine for a few minutes, then
check and top up the oil level.
Pistons/connecting rods -
removal and refitting#
84Remove the sump pan.
85Unbolt and remove the oil pump
pick-up/filter screen assembly.
86The big-end bearing shells can be
renewed without having to remove the
cylinder head if the caps are unbolted and the
piston/connecting rod pushed gently about
one inch up the bore (the crankpin being at its
lowest point). If these shells are worn,however, the main bearing shells will almost
certainly be worn as well, necessitating a
complete overhaul, including crankshaft
removal.
87To remove the piston/connecting rods,
the cylinder head must be removed.
88The big-end caps and their connecting
rods are numbered 1, 2, 3 and 4 from the
timing cover end of the engine. The numbers
are located either side of the rod/cap joint on
the engine oil dipstick tube side (photo).
89Turn the crankshaft as necessary to bring
the first connecting rod big-end crankpin to its
lowest point, then unscrew the cap bolts and
remove the cap and shell bearing.
90Push the connecting rod/piston assembly
up the bore and out of the cylinder block.
There is one reservation; if a wear ridge has
developed at the top of the bores, remove this
by careful scraping before trying to remove
the piston/rod assemblies. The ridge will
otherwise prevent removal, or break the
piston rings during the attempt.
91Remove the remaining piston/connecting
rods in a similar way. If the bearing shells are
to be used again, tape them to their
respective caps or rods.
92Removal of the piston rings and
separation of the piston from the connecting
rod is covered in the next sub-Section.
93Fit the bearing shells into the connecting
rods and caps, ensuring that the recesses into
which the shells seat are clean and dry.
94Check that the piston ring gaps are evenly
spaced at 120º intervals. Liberally oil the rings
and the cylinder bores.95Fit a piston ring clamp to compress the
rings, oiling the rings and the clamp interior
surfaces liberally.
96Insert the first piston/connecting rod into
its cylinder bore. Make sure that the assembly
is the correct one for its particular bore. The
cap and rod matching numbers must be
towards the engine oil dipstick guide tube and
the arrow on the piston crown towards the
timing belt (photo).
97Push the piston into the bore until the
piston ring clamp is against the cylinder block
and then tap the crown of the piston lightly to
push it out of the ring clamp and into the bore
(photo).
98Oil the crankshaft journal and fit the
big-end of the connecting rod to the journal.
Check that the bearing shells are still in
position, then fit the big-end cap and bolts;
check that the cap is the right way round
(photo).
Supplement: Revisions and information on later models 13•25
5B.78 Fitting the oil pump5B.77B Using a socket to fit the new oil
pump oil seal5B.77A Removing the oil pump seal
5B.98 Fitting a big-end bearing cap
5B.88 Connecting rod and cap numbers
5B.97 Fitting a piston/connecting rod5B.96 Piston directional arrow
13

99Tighten the big-end bolts to the specified
torque (photo). The correct torque is
important as the bolts have no locking
arrangement. After tightening each big-end,
check that the crankshaft rotates smoothly.
100Repeat the operations on the remaining
piston/rod assemblies.
101Refit the oil pump pick-up assembly
using a new sealing ring.
102Refit the sump pan and the cylinder head
as described in earlier sub-Sections.
103Fill the engine with oil and coolant.
Pistons/connecting rods -
separation and piston
ring renewal
ª
104If the piston/connecting rods have been
removed in order to renew the piston rings,
refer to Chapter 1, Section 18, but note thatthe piston rings should be fitted so that the
word TOP is uppermost.
105If new pistons are to be fitted, it is
recommended that the gudgeon pins are
removed and refitted by a FIAT dealer as the
connecting rods must be carefully heated in
order to be able to push the gudgeon pin out
of the rod small-end, change the piston and
push the pin back into position. Locating the
gudgeon pin will require a special tool. The
gudgeon pin is a sliding fit in the piston but an
interference fit in the connecting rod.
106Refer to Fig. 13.6 for the correct
assembly of the piston and connecting rod.
Engine/transmission mountings
- renewal
107Refer to Chapter 1, Section 33. Three
mountings are used (photos).
PART C: ENGINE REMOVAL
AND DISMANTLING
Method of removal - general
1The engine, complete with transmission,
should be removed upwards out of the engine
compartment.
Engine/transmission -
removal and separation #
Warning: Refer to the beginning
of Section 9 before starting any
work.
2Mark the position of the hinges on the
underside of the bonnet and then, with the
help of an assistant, unscrew the hinge bolts
and lift the bonnet to a safe storage area.
3Drain the coolant; a cylinder block drain
plug is not fitted.
4Drain the engine and transmission oils.
5Disconnect the battery, negative lead first.
6Remove the air filter.
7Disconnect the radiator hoses from the
engine (photos).
13•26 Supplement: Revisions and information on later models
5C.7B Radiator hose at thermostat
housing5C.7A Radiator hose connection to coolant
distribution tube5B.107C Right-hand engine mounting
5B.107B Left-hand rear
engine/transmission mounting5B.107A Left-hand front
engine/transmission mounting
Fig. 13.6 Piston/connecting rod correctly
assembled - 999 and 1108 cc engine
(Sec 5B)
1 Piston grade (A) and directional arrow on
piston crown (towards timing belt)
2 Rod/cap matching numbers
3 Gudgeon pin offset in piston (0.9 to 1.1 mm)
Arrow indicates crankshaft rotation direction
Fig. 13.5 Piston ring arrangement on the
999 cc engine (Sec 5B)5B.99 Tightening a big-end cap bolt

can be lowered to rest on the exhaust and
bodymember.
34Continue to raise the engine and the
transmission until it can be removed from the
engine compartment and placed on the work
surface (photo).
35Clean the exterior of the engine and
transmission by steam cleaning or using a
water soluble solvent.
36Unbolt and remove the starter motor.
37Unscrew the flywheel housing-to-engine
flange bolts. Note the location of the engine
lifting lug.
38Unbolt and remove the lower cover plate
from the flywheel housing.
39Pull the transmission from the engine. It is
located by two hollow dowels and one stud
(photo).
Dismantling - general
40Refer to Chapter 1, Section 14.
Complete dismantling#
Warning: Refer to the beginning
of Section 9 before starting any
work.
41Unbolt and remove the camshaft cover.
42Unbolt and remove the timing belt cover.
43Remove the distributor (Section 10).
44Remove the hot air collector and the
exhaust manifold.
45Release, disconnect and remove the
coolant distribution pipe from the rear of the
coolant pump.46Unscrew and discard the oil filter
cartridge.
47Unbolt the thermostat housing, discard
the joint gasket.
48Remove the fuel pump, together with its
insulator block and actuating pushrod, if
applicable.
49Remove the carburettor, or throttle body,
as appropriate.
50Remove the inlet manifold and discard the
joint gasket.
51Remove the alternator and its drivebelt
and withdraw the engine oil dipstick.
52Unbolt and remove the crankshaft pulley.
53Unbolt and remove the timing belt
tensioner.
54Remove the timing belt.
55Unbolt and remove the coolant pump.
56Remove the cylinder head.
57Remove and discard the cylinder head
gasket.
58Remove the clutch.
59Lock the flywheel starter ring gear teeth
and remove the crankshaft sprocket bolt and
sprocket.
60Unbolt and remove the sump pan,
then the exhaust pipe support bracket
(photos).
61Prevent rotation of the crankshaft by
locking the starter ring gear teeth and then
unbolt and remove the flywheel. The flywheel
can only be fitted in one position as it is
located on a dowel.
62Remove the engine rear plate. Note thesmall socket-headed screw which holds the
timing index plate (photo).
63Unbolt and remove the oil pump pick-up
assembly, followed by the oil pump itself.
64Turn the engine on its side and remove
the piston/connecting rod assemblies.
65Stand the engine on its cylinder block
machined face, and then unbolt and remove
the crankshaft rear oil seal retainer. Discard
the gasket.
66Note the markings on the main bearing
caps. One line on the cap nearest the timing
belt, then two, C for centre cap, then three
and four (photo).
67The caps will only fit one way round.
68Unbolt the main bearing caps, removing
them with the shell bearings.
69Lift the crankshaft from the crankcase and
remove the bearing half shells from the
Supplement: Revisions and information on later models 13•29
5C.39 Separating the engine and
transmission5C.34 Lifting out the engine and
transmission5C.32 Right-hand engine mounting
brackets on body and engine
5C.66 Main bearing cap markings
5C.60A Removing the sump pan
5C.62 Unscrewing socket-head screw
from timing index plate5C.60B Exhaust pipe support bracket
attached to crankcase
13

crankcase. If the shells are to be used again,
keep them with their respective bearing caps.
70The thrust washers which control
crankshaft endfloat are located in the
crankcase, and retained by the turned-over
edges of the centre main bearing shell.
71The engine is now fully stripped.
Examination and renovation
72The procedures for the following items are
essentially as described in Chapter 1, Sec-
tion 18.
Cylinder block and crankcase
Crankshaft and bearings
Flywheel
Oil seals and gaskets
Cylinder head
73Using a straight-edge, check the cylinder
head gasket surface for distortion. If it
exceeds the specified tolerance, it must be
surface ground by your dealer.74Refer to Chapter 1, Section 39, for
dismantling and renovation operations. Note
that single valve springs are fitted.
Oil pump
75Checking operations are described in
sub-Section B.
Pistons and connecting rods
76Refer to sub-Section B.
77If one or more connecting rods are
changed, it is important that its weight is
identical to that of the original. Use an
accurate balance to weigh them and remove
metal if necessary from the new rod in the
areas indicated in Fig. 13.7.
Camshaft and cam followers
78If the camshaft journals or bearings show
any sign of wear or scoring, then the
camshaft, or cylinder head, or both must be
renewed.
79The cam followers should be checked for
ovality using a micrometer. Unless unworn
they should be renewed.
Timing belt tensioner and timing belt
80The tensioner is a lubricant-sealed pulley,
and it should be tested for smooth and quiet
operation by turning it with the fingers. Any
evidence of roughness or rattle will indicate
the need for a new assembly (photo).81The timing belt should be inspected at
regular intervals for correct adjustment and
condition (see Section 3 or “Routine
maintenance” at the beginning of the Manual).
If there is evidence of worn teeth, cracking or
fraying, or oil contamination, renew the belt.
The vehicle manufacturers recommend that
the belt is renewed whenever it is removed,
and it should certainly be renewed at the
intervals specified in Section 3 or the main
“Routine maintenance” section at the
beginning of this Manual as a precautionary
measure against belt breakage and
consequent expensive engine damage.
PART D:
ENGINE REASSEMBLY AND
REFITTING
Reassembly - general
1Refer to Chapter 1, Section 19.
Complete reassembly#
2With the cylinder block/crankcase standing
on the work surface, fit the bearing half shells
into their crankcase seats (photo). Make sure
that the seats are perfectly clean as dirt or grit
trapped under the shell will cause binding
when the crankshaft is turned.
3The centre bearing crankcase web
incorporates the thrust washers held by the
lips of the bearing shell (photo).
4Oil the shells and lower the crankshaft into
the crankcase (photo).
5Fit the bearing shells into the main bearing
caps, again making sure that the shell seats
are perfectly clean (photo).
13•30 Supplement: Revisions and information on later models
5D.5 Main bearing cap and shell5D.4 Fitting the crankshaft5D.3 Crankshaft thrust washer at centre
bearing
5D.2 Main bearing shell in crankcase
Fig. 13.8 Checking a cam follower for
ovality - 999 and 1108 cc engine (Sec 5C)
Fig. 13.7 Metal removing areas (arrowed)
on connecting rod - 999 and 1108 cc
engine (Sec 5C)
5C.80 Timing belt tensioner