converter with the exception of the catalyst. See Fig. 5. The TWC
converter uses rhodium, with or without platinum, as its catalyst.
Rhodium helps reduce NOx emissions, as well as HC and CO.
Visually check for presence of catalytic converter(s). Also
check for presence of any required air supply system for the oxidizing
section of the converter. Check for external damage such as severe
dents, removed or damaged heat shields, etc. Check for pellets or
pieces of converter in the tailpipe.
Three-Way Catalyst + Oxidation Catalyst (TWC + OC)
This system contains a TWC converter and an OC converter in a
common housing, separated by a small air space. See Fig. 6. The 2
catalysts are referred to as catalyst beds. Exhaust gases pass through
the TWC first. The TWC bed performs the same function as it would as a
separate device, reducing all 3 emissions. As exhaust gases leave the
bed, they pass through the air space and into the second (OC)
converter catalyst bed.
Visually check for presence of catalytic converter(s). Check
for external damage such as severe dents, removed or damaged heat
shields, etc. Check for pellets or pieces of converter in the
tailpipe.
Fig. 6: Typical Three-Way + Oxidation Catalytic Converter
Courtesy of General Motors Corp.
FILL PIPE RESTRICTOR (FR)
A fuel tank fill pipe restrictor is used to prohibit the
introduction of leaded fuel into the fuel tank. Unleaded gasoline pump
dispensers have a smaller diameter nozzle to fit fuel tank of vehicle
requiring the use of unleaded fuel (vehicles equipped with catalytic
converter).
Visually inspect fill pipe restrictor(s) for tampering, i.e.,\
restrictor is oversize or the flapper is non-functional. If vehicle is
equipped with an auxiliary fuel tank, ensure auxiliary fuel tank is
also equipped with a fill pipe restrictor.
EXHAUST GAS RECIRCULATION (EGR) SYSTEM
CYLINDER BLOCK
* PLEASE READ THIS FIRST *
NOTE: Always refer to appropriate engine overhaul article in the
ENGINES section for complete overhaul procedures and
specifications for the vehicle being repaired.
BLOCK CLEANING
Only cast cylinder blocks should be hot tank cleaned.
Aluminum cylinder blocks should be cleaned using cold tank method.
Cylinder block is cleaned in order to remove carbon deposits, gasket
residue and water jacket scale. Remove oil galley plugs, freeze plugs
and cam bearings prior to block cleaning.
BLOCK INSPECTION
Visually inspect the block. Check suspected areas for cracks
using the Dye Penetrant inspection method. Block may be checked for
cracks using the Magnaflux method.
Cracks are most commonly found at the bottom of the
cylinders, the main bearing saddles, near expansion plugs and between
the cylinders and water jackets. Inspect lifter bores for damage.
Inspect all head bolt holes for damaged threads. Threads should be
cleaned using tap to ensure proper head bolt torque. Consult machine
shop concerning possible welding and machining (if required).
CYLINDER BORE INSPECTION
Inspect the bore for scuffing or roughness. Cylinder bore
is dimensionally checked for out-of-round and taper using dial bore
gauge. For determining out-of-round, measure cylinder parallel and
perpendicular to the block centerline. Difference in the 2 readings
is the bore out-of-round. Cylinder bore must be checked at top, middle
and bottom of piston travel area.
Bore taper is obtained by measuring bore at the top and
bottom. If wear has exceeded allowable limits, block must be honed
or bored to next available oversize piston dimension.
CYLINDER HONING
Cylinder must be properly honed to allow new piston rings to
properly seat. Cross-hatching at correct angle and depth is critical
to lubrication of cylinder walls and pistons.
A flexible drive hone and power drill are commonly used.
Drive hone must be lubricated during operation. Mix equal parts of
kerosene and SAE 20w engine oil for lubrication.
Apply lubrication to cylinder wall. Operate cylinder hone
from top to bottom of cylinder using even strokes to produce 45 degree
cross-hatch pattern on the cylinder wall. DO NOT allow cylinder hone
to extend below cylinder during operation.
Recheck bore dimension after final honing. Wash cylinder
wall with hot soapy water to remove abrasive particles. Blow dry with
compressed air. Coat cleaned cylinder walls with lubricating oil.
DECK WARPAGE
Check deck for damage or warped head sealing surface. Place
a straightedge across gasket surface of the deck. Using feeler gauge,
measure clearance at center of straightedge. Measure across width and
Application Front - In. (mm) Rear - In. (mm\
)
Gas Engine With
14" & 15" Wheels (1) ....... 29.04-29.82
(737.5-757.5) .......... 29.76-30.54\
(756.0-776.0)\
Gas Engine With 15",
16" & 17" Wheels ( 2) ....... 29.27-30.05
(743.5-765.5) ........... 30.0-30.78\
(762.0-782.0)\
CNG & Electric Vehicles ..... 30.46-31.24
(783.5-803.5) ........... 31.2-31.98\
(792.5-812.5)\
( 1) - With tire sizes P205/75R 15 and P215/65R 15.
( 2) - With tire sizes P215/70R 15, P215/65R 16 and 215/65R 17.
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HOIST
CAUTION: On Ram Van/Wagon, ensure there is adequate drive shaft
clearance while raising vehicle. DO NOT raise vehicle by
hoisting or jacking against front lower control arms. If rear
axle, fuel tank, spare tire and liftgate will be removed for
service, place additional weight on rear end of vehicle. This
will prevent tipping as center of gravity changes.
Caravan, Ram Van/Wagon, Town & Country, & Voyager
To raise vehicle on single and twin post type hoists, ensure
hoist pads contact vehicle frame behind front control arm pivots and
inside rear wheels on rear axle housing. Always use hoist adapters.
See Fig. 2 or 5.
Dakota & Ram Pickup
Vehicle may be raised on single or twin post swiveling arm,
or ramp-type drive hoists. If using swiveling arm hoist, ensure
lifting arms, pads or ramps are positioned evenly on frame rails, and
adequate clearance is maintained for transfer case (4WD models) or
skid plate. All hoists must be equipped with adapters to properly
support vehicle. See Fig. 3.
WHEEL ALIGNMENT PROCEDURES
FRONT WHEEL CAMBER & CASTER ADJUSTMENT
CAUTION: DO NOT adjust caster by heating or bending suspension
components. If caster angle is incorrect, replace
component(s) causing incorrect angle.
Caravan, Town & Country, & Voyager
1) Caster is factory preset and cannot be adjusted. Camber is
factory preset, but can be adjusted with a camber service kit. Raise
and support vehicle. While holding lower strut attaching bolts
stationary, loosen attaching nuts. See Fig. 6. Remove upper attaching
nut and bolt. Install camber service kit attaching/adjusting bolt and
nut. While holding bolt stationary, lightly tighten nut. Repeat
procedure for lower attaching nut and bolt.
2) Lower vehicle until vehicle weight is supported by
suspension. Bounce vehicle several times and allow suspension to
settle. Rotate new cam bolt to move top of wheel in or out to
specified camber. See WHEEL ALIGNMENT SPECIFICATIONS table. Tighten
through-bolt nuts to specification. See TORQUE SPECIFICATIONS table.