MITSUBISHI MONTERO 1991 Service Manual

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3.0 L V 6 - V IN S [ B ,C ,S ]

1 991 M it s u bis h i M onte ro
1991 ENGINES
Mitsubishi 3.0L V6
Montero, Pickup, 3000GT
* PLEASE READ THIS FIRST *
NOTE: For engine repair procedures not covered in this article,
see ENGINE OVERHAUL PROCEDURES - GENERAL INFORMATION article
in the GENERAL INFORMATION section.
ENGINE IDENTIFICATION
Engine may be identified by using Vehicle Identification
Number (VIN) stamped on a metal pad, located near lower left corner of\
windshield. The eighth character identifies the engine model.
Engine model number is stamped on front upper edge of
cylinder block (below cylinder head) or on vehicle information plate
on firewall. Engine serial number is stamped near the engine model
number.
ENGINE IDENTIFICATION CODES TABLE









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Application Engine Model Engine Code
3.0L V6 SOHC
Montero ............... 6G72 .................... S
Pickup ................ 6G72 .................... S
3.0L V6 DOHC
3000GT
Non-Turbo ............ 6G72 .................... B
Turbo ................ 6G72 .................... C









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ADJUSTMENTS
VALVE CLEARANCE ADJUSTMENT
NOTE: Hydraulic lash adjusters are set into rocker arms (SOHC) or
cylinder head (DOHC). No adjustment is required.
REMOVAL & INSTALLATION
NOTE: For reassembly reference, label all electrical connectors,
vacuum hoses and fuel lines before removal. Also place
mating marks on engine hood and other major assemblies
before removal.
FUEL PRESSURE RELEASE
Perform these steps to release fuel system pressure:
* Disconnect fuel pump harness connector at fuel tank.
* Start engine. After it stalls, turn ignition switch to OFF
position.
* Disconnect battery (-) terminal, and reconnect fuel pump
harness connector.

* Wrap shop towels around fuel return and high pressure hoses
to prevent fuel splashing on engine. Disconnect fuel return
hose and high pressure fuel hose to drain any residual fuel.
ENGINE
Removal (Montero & Pickup)
1) Remove hood. Drain cooling system, and remove radiator.
Remove skid plate and splash shields. Release fuel system pressure.
See FUEL PRESSURE RELEASE under REMOVAL & INSTALLATION. Disconnect
negative battery cable.
2) Remove air cleaner ducts. Remove accessory drive belts.
Remove and support A/C compressor and power steering pump. DO NOT
disconnect hoses from compressor or pump. Disconnect oil cooler hoses.
Cover fuel hose using shop towel, and disconnect high pressure fuel
hose and "O" ring. Remove fuel return hose.
3) Label and disconnect all vacuum hoses. Disconnect cooling
system hoses. Label and disconnect all electrical connections from
engine. Remove heat shield from motor mounts. Remove motor mount
bolts. Ensure all hoses and wires are disconnected and set aside.
4) Disconnect exhaust pipe from exhaust manifolds. Remove
starter. Attach engine hoist to engine. Support transmission.
Disconnect engine from transmission. See appropriate article in
CLUTCHES or TRANSMISSION SERVICING. Remove engine.
Installation (Montero & Pickup)
To install, reverse removal procedure. Install new "O" ring
on fuel line. Install new exhaust gaskets and nuts. See TORQUE
SPECIFICATIONS (MONTERO & PICKUP) table at end of article. Adjust
fluid levels.
Removal (3000GT)
1) Release fuel pressure. See FUEL PRESSURE RELEASE under
REMOVAL & INSTALLATION. Remove hood. Remove cruise control vacuum pump
and linkage. On turbo models, remove necessary turbo air intake hoses
and pipes. On all other models, remove air cleaner hoses.
2) On all models, drain cooling system. Drain engine oil and
transaxle oil. Remove heater hoses and radiator hoses. Remove
transaxle assembly. See appropriate article in CLUTCHES or
TRANSMISSION SERVICING.
3) Remove radiator. Label and disconnect all vacuum hoses.
Label and disconnect all electrical connections and harnesses from
engine. Remove accessory drive belts.
4) Remove and support A/C compressor and power steering pump.
DO NOT disconnect hoses from compressor or pump. Cover fuel hose using
shop towel, and disconnect high pressure fuel hose and "O" ring.
Remove fuel return hose.
5) On turbo models, disconnect oil cooler and vacuum hoses.
On all models, remove motor mount bolts and brackets. Ensure all hoses
and wires are disconnected and set aside. Attach engine hoist to
engine. Remove engine.
Installation
To install, reverse removal procedure. Install new "O" ring
on fuel line. Install new exhaust gaskets and nuts. See TORQUE
SPECIFICATIONS (3000GT) table at end of article. Adjust fluid levels.
UPPER INTAKE MANIFOLD
Removal (Montero & Pickup)
1) Remove air intake hose. See Fig. 1. Remove accelerator
cable adjusting bolts. On models equipped with automatic transmission,
remove throttle control cable. On all models, remove accelerator

cable. Label and disconnect all vacuum hoses from throttle body and
upper intake manifold.
2) Disconnect O2 sensor connector. Remove EGR pipe and
gasket. Remove ignition coil. Remove engine oil filler neck bracket.
Remove throttle body, leaving coolant hoses connected. Remove throttle
body gasket. Remove upper intake manifold plenum mounting bolts and
nuts.
3) If necessary, remove EGR valve and pipe. Remove upper
intake manifold plenum brackets. Remove upper intake manifold and
gasket.
Inspection & Installation (Montero & Pickup)
Clean all gasket mating surfaces. Inspect for damage and
cracks on all mounting surfaces. To install, reverse removal procedure
using new gaskets. Tighten bolts and nuts to specification. See TORQUE
SPECIFICATIONS (MONTERO & PICKUP) table at end of article.
Fig. 1: Exploded View of Upper Intake Manifold & Components (DOHC)
Courtesy of Mitsubishi Motor Sales of America, Inc

Fig. 2: View of Upper Intake Manifold & Components (DOHC Turbo, SOHC)\
Courtesy of Mitsubishi Motor Sales of America, Inc
Removal (3000GT)
1) Remove air intake hose. Remove throttle body and gasket
with control cables and coolant and vacuum hoses attached. See Fig. 2.
2) Remove EGR and EGR pipe (if equipped). Disconnect power
brake hose. Label and disconnect vacuum hoses and electrical
connections. Remove upper intake manifold plenum retaining bracket(s),\
mounting bolts and nuts. Remove upper intake manifold.
Inspection & Installation (3000 GT)
Clean all gasket mating surfaces. Inspect for damage and
cracks on all mounting surfaces. To install, reverse removal procedure
using new gaskets. Install throttle body gasket with projection on
gasket facing upward beyond throttle body mounting surface. Tighten
bolts and nuts to specification. See TORQUE SPECIFICATIONS (3000GT)
table at end of article.
LOWER INTAKE MANIFOLD
CAUTION: Fuel system is under pressure. Fuel pressure must be

released before disconnecting fuel lines.
Removal
1) Release fuel pressure. See FUEL PRESSURE RELEASE under
REMOVAL & INSTALLATION. Remove upper intake manifold. See UPPER INTAKE
MANIFOLD under REMOVAL & INSTALLATION.
2) Drain cooling system. Remove high pressure and return fuel
lines. Cover fuel lines using shop towel during removal as some fuel
may be retained. Remove vacuum hose from pressure regulator.
Disconnect injector harness from injectors.
3) Remove fuel delivery pipe, fuel injectors and pressure
regulator. See Fig. 3. DO NOT allow injectors to fall from delivery
pipe during removal. Remove vacuum hose and pipe assembly.
4) On Montero & Pickup, disconnect coolant temperature
sending unit, coolant temperature switch (A/C equipped), coolant
temperature sensor and thermoswitch (A/T equipped). Disconnect upper
radiator and coolant by-pass hoses. Disconnect heater pipe. On all
models, remove intake manifold and gasket.
Fig. 3: Exploded View of Lower Intake Manifold & Components
Courtesy of Mitsubishi Motor Sales of America, Inc.
Inspection & Installation
1) Inspect for damage and cracks on all mounting surfaces. To

install, reverse removal procedure using new gaskets and "O" rings.
Coat "O" ring with fuel before installation.
2) Install lower intake manifold gasket with adhesive side
toward intake manifold and gasket protrusions facing outboard of
engine. Tighten bolts and nuts to specification. See appropriate
TORQUE SPECIFICATIONS table at end of article. Check for fuel leaks.
TURBOCHARGER
Removal (Front)
1) Drain coolant, and remove radiator. Disconnect exhaust
pipe from turbo. Remove all air intake pipes. Note match marks and
installation depth on air pipes and hoses for reinstallation. Remove
serpentine drive belt. Remove alternator. Remove A/C compressor and
bracket, and support aside.
2) Remove O2 sensor. Remove dipstick assembly and turbo heat
shield. Disconnect turbo coolant feed and return lines. Disconnect
turbo oil feed and return lines. Remove turbocharger assembly.
Removal (Rear)
1) Drain coolant. Remove battery. Disconnect accelerator
cable at bracket and throttle body. Disconnect exhaust pipe from
turbo. Remove all air intake pipes and heat shields. Disconnect
accelerator cable at pedal.
2) Remove clutch booster vacuum hose. Remove O2 sensor.
Remove EGR pipe and turbo heat shield. Disconnect turbo coolant feed
and return lines. Disconnect turbo oil feed and return lines. Remove
turbocharger assembly.
CAUTION: DO NOT allow foreign material into turbocharger air intakes
or coolant and oil passages.
Inspection (Front & Rear)
1) Inspect turbocharger for oil leakage. Check turbine and
compressor wheels for cracks and other damage. Both wheels should turn
easily by hand.
2) Apply 6.8 psi (61 kPa) vacuum to wastegate diaphragm.
Ensure wastegate operates and diaphragm holds vacuum pressure. Use
care when cleaning gasket surfaces so no foreign material enters
turbocharger oil, coolant and air passages.
Installation (Front & Rear)
Refill turbocharger with clean engine oil through oil pipe
installation hole. To complete installation, reverse removal
procedure. Align match marks, and install air pipes and hoses to
proper depth.
EXHAUST MANIFOLDS
Removal (Montero & Pickup)
1) Remove splash shields. Remove O2 sensor. Remove exhaust
pipe-to-manifold nuts. Lower exhaust pipe, and remove gasket. Remove
heat protector. To remove right exhaust manifold, remove air duct,
engine lift bracket and alternator bracket.
2) To remove left exhaust manifold, remove EGR pipe and
gasket. Remove front intake manifold plenum bracket. Remove exhaust
manifolds and gaskets.
Inspection (Montero & Pickup)
Clean all gasket mating surfaces. Inspect for damage and
cracks on all mounting surfaces. Check mounting surfaces of manifold
and cylinder head for warpage. Repair or replace components if warpage
exceeds .012" (.30 mm).

Installation (Montero & Pickup)
To install, reverse removal procedure using new gaskets.
Tighten bolts and nuts to specification. See TORQUE SPECIFICATIONS
(MONTERO & PICKUP) table at end of article.
Removal (3000GT)
1) Remove turbocharger(s) (if equipped). See TURBOCHARGER
under REMOVAL & INSTALLATION. On front manifold, remove serpentine
drive belt and alternator. Remove oil dipstick. On rear manifold,
remove EGR pipe (if equipped).
NOTE: Note locations and direction of installation of exhaust
manifold plain and spring washers for reinstallation
reference. DO NOT mix these fasteners.
2) On all manifolds, remove exhaust pipe-to-manifold nuts.
Lower exhaust pipe, and remove gasket. Remove heat protector. Remove
exhaust manifold nuts and washers. Note locations and direction of
installation of plain and spring washers for reinstallation reference.
DO NOT mix these fasteners. Remove exhaust manifold and gasket.
Inspection (3000GT)
Clean all gasket mating surfaces. Inspect for damage and
cracks on all mounting surfaces. Check mounting surfaces of manifold
and cylinder head for warpage. Repair or replace components if warpage
exceeds .012" (.30 mm).
Installation (3000GT)
To install, reverse removal procedure using new gaskets.
Install new "O" ring on dipstick guide. Coat "O" ring with oil before
installation. Install manifold nuts and washers in original locations.
Tighten nuts to specification in sequence. See Fig. 4. See TORQUE
SPECIFICATIONS (3000GT) table at end of article.
Fig. 4: Exhaust Manifold Tightening Sequence (3000GT)
Courtesy of Mitsubishi Motor Sales of America, Inc.
CYLINDER HEADS

Removal (SOHC)
1) Drain cooling system. Remove upper and lower intake
manifolds and brackets. See UPPER INTAKE MANIFOLD and LOWER INTAKE
MANIFOLD under REMOVAL & INSTALLATION. Remove spark plug wires. Remove
splash shields.
2) Disconnect O2 sensor. Disconnect exhaust pipe from exhaust
manifold, and support to crossmember using wire. Remove heat shields
and exhaust manifolds. See EXHAUST MANIFOLDS under REMOVAL &
INSTALLATION.
3) Remove distributor (left or rear head). Remove timing bel\
t
outer covers, camshaft sprockets, timing belt and timing belt inner
covers. See TIMING BELT under REMOVAL & INSTALLATION. Remove accessory
bracket bolts from front of cylinder head. Remove rocker cover and
gasket.
4) Using Socket (MD998051), loosen cylinder head bolts in 2-\
3
steps using proper sequence. See Fig. 5. Remove cylinder head and
camshaft assemblies. Note direction of washer installation on head
bolts.
NOTE: Cylinder head bolts must be loosened in 2-3 steps using
proper sequence to prevent cylinder head warpage and
cracking.
Fig. 5: Cylinder Head Bolt Removal & Tightening Sequence
Courtesy of Mitsubishi Motor Sales of America, Inc.
Inspection (SOHC)
Check cylinder head height and warpage at gasket and manifold

surfaces. Resurface head if warpage exceeds specification. See
CYLINDER HEAD (SOHC) table under ENGINE SPECIFICATIONS at end of
article. Replace cylinder head if it is not within specification after
resurfacing.
Installation (SOHC)
1) Ensure mating surfaces are clean and dry. Note
identification mark located on front of head gasket. Identification
marks are: "R" for SOHC, "2DN" for DOHC non-turbocharged and "2DT" for
DOHC turbocharged engine. Install head gasket with identification mark
toward timing belt side of engine and facing upward. Ensure all holes
are aligned.
NOTE: Install head gasket with identification mark toward timing
belt side of engine and facing upward. Ensure all holes
align. Install washers on head bolts with chamfered side
toward bolt head.
2) Install cylinder head and bolts. Ensure washers are
installed on head bolts with chamfered side toward bolt head. Using
proper sequence, tighten bolts to specification in 2-3 steps. See
Fig. 5 . See appropriate TORQUE SPECIFICATIONS table at end of article.
3) Apply sealant to rocker cover sealing surfaces before
installation. See Fig. 6. Ensure rocker cover gasket projections are
aligned with notches in rocker cover. Coat all "O" rings with oil, and
install a new "O" ring on distributor adapter and oil dipstick tube.
4) Coat camshaft area with oil prior to installing
distributor adapter. To complete installation, reverse removal
procedure. Tighten bolts and nuts to specification. See appropriate
TORQUE SPECIFICATIONS table. After engine reaches normal operating
temperature, allow engine to cool, and retighten cylinder head bolts.
Fig. 6: Applying Sealant to Rocker Cover (SOHC)
Courtesy of Mitsubishi Motor Sales of America, Inc.
Removal (DOHC)
1) Drain cooling system. Remove upper and lower intake
manifolds and brackets. See UPPER INTAKE MANIFOLD and LOWER INTAKE
MANIFOLD under REMOVAL & INSTALLATION.
2) Remove turbocharger(s) (if equipped). See TURBOCHARGER
under REMOVAL & INSTALLATION. Remove heat shields from exhaust
manifolds. Remove exhaust manifolds. See EXHAUST MANIFOLDS under
REMOVAL & INSTALLATION.
3) Remove spark plug wires and ignition coils. Remove rocker
cover and gasket. Remove timing belt and timing belt inner covers. See

TIMING BELT under REMOVAL & INSTALLATION. Remove intake camshaft
sprockets.
4) Remove coolant manifold and coolant inlet pipe. Using
Socket (MD998051), remove cylinder head bolts. Remove cylinder head
and camshaft assemblies. Note direction of washer installation on head
bolts.
Inspection (DOHC)
Check cylinder head height. Check warpage at gasket and
manifold surfaces. Resurface head if warpage exceeds specification.
See CYLINDER HEAD (DOHC) table under ENGINE SPECIFICATIONS at end of
article. After resurfacing, recheck cylinder head height. Replace
cylinder head if it is not within specification.
Installation (DOHC)
1) Ensure mating surfaces are clean and dry. Note
identification mark located on front of head gasket. Identification
marks are: "R" for SOHC, "2DN" for DOHC non-turbocharged and "2DT" for
DOHC turbocharged engine. Install head gasket with identification mark
toward timing belt side of engine and facing upward. Ensure all holes
are aligned.
NOTE: Install head gasket with identification mark toward timing
belt side of engine and facing upward. Ensure all holes
align. Install washers on head bolts with chamfered side
toward bolt head.
2) Install cylinder head and bolts. Ensure washers are
installed on head bolts with chamfered side toward bolt head. Using
proper sequence, tighten bolts to specification in 2-3 steps. See
Fig. 5 . See TORQUE SPECIFICATIONS (3000GT) table at end of article. On
turbocharger equipped engines, back off head bolts once, and repeat
tightening procedure.
3) To reinstall camshaft sprocket, hold hexagonal area of
camshaft using wrench while tightening sprocket bolt. Tighten rocker
cover bolts in a crisscross pattern. Start at 4 corners of rocker
cover and move toward center.
NOTE: Rocker cover bolts are color coded. Front cylinder bank
bolts are black; rear cylinder bank bolts are green.
4) To complete installation, reverse removal procedure.
Tighten bolts and nuts to specification. See TORQUE SPECIFICATIONS
(3000GT) table.
FRONT CRANKSHAFT OIL SEAL
Removal & Installation
Remove timing belt and crankshaft sprocket. See TIMING BELT
under REMOVAL & INSTALLATION. Pry oil seal from oil pump. To install,
coat seal lip with grease. Using Seal Installer (MD998717), install
seal in oil pump. Install remaining components. See appropriate TORQUE
SPECIFICATIONS table at end of article.
TIMING BELT
Removal (Montero & Pickup)
1) Drain cooling system. Disconnect upper radiator hose.
Remove upper radiator shroud. Remove cooling fan and fan clutch
assembly. Remove cooling fan pulley. Remove all drive belts. Remove
power steering pump with pressure and return hoses connected, and set
aside.
2) Remove power steering pump brackets. Remove A/C tensioner