3.1L v6 - Vins [M,t] Buick Century V

ENGINE IDENTIFICATION

Note. For engine repair procedures not covered in this article, see ENGINE OVERHAUL PROCEDURES - GENERAL INFORMATION article in the GENERAL INFORMATION section.

Engine may be identified by Vehicle Identification Number (VIN), engine block code or partial VIN. (Scheme 11)and (Scheme 12). VIN is stamped on a metal pad located near lower left corner of windshield. Eighth character of VIN identifies engine model (M or T indicates 3.1L PFI engine). Tenth character of VIN identifies model year (R indicates 1994 model year).

For VIN M, engine ID label will be found in center of left rocker cover and at left rear of oil pan. VIN will be found stamped on right or left side of cylinder block, at cylinder block-to-transaxle/transmission flange and at front of block above timing cover. (Scheme 11) (L82 indicates VIN M, 3.1L PFI engine).

For VIN T, engine block code (3 characters) is stamped on left side of cylinder block, at cylinder block-to-transaxle/transmission flange (LHO indicates VIN T, 3.1L PFI engine). (Scheme 12)

Partial VIN (9 characters) is stamped on left side of cylinder block, at cylinder block-to-transaxle/transmission flange. (Scheme 12) First character of partial VIN identifies manufacturer (1 for Chevrolet, 2 for Pontiac, 3 for Oldsmobile and 4 for Buick). Second character identifies model year (R indicates 1994 model year).

ENGINE IDENTIFICATION CODES

Scheme 11

Scheme 12

VALVE CLEARANCE ADJUSTMENT

Note. If valves and seats are reconditioned, install adjustable rocker arm studs. Adjustment procedure is for adjustable rocker arm studs only. Engines with original rocker arms studs are not adjustable.

1. Bring No. 1 cylinder to firing position and align timing marks on front cover and harmonic balancer. Adjust exhaust valves on cylinders No. 1, 2 and 3 by backing off adjusting nut until valve lash is felt at push rod.
2. Tighten adjusting nut (while rotating push rod) until all valve lash is eliminated. Tighten adjusting nut an additional 1 1/2 turns. Repeat adjustment on intake valves for cylinders No. 1, 5 and 6.
3. Turn engine one revolution to cylinder No. 4 firing position. Adjust exhaust valves on cylinders No. 4, 5 and 6. Adjust intake valves on cylinders No. 2, 3 and 4.

TROUBLE SHOOTING

Note. See TROUBLE SHOOTING - BASIC PROCEDURES article in the GENERAL TROUBLE SHOOTING section.

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

Disconnect negative battery cable. Loosen fuel tank filler cap. Connect Fuel Pressure Gauge (J-34730-1) to fuel line fitting (wrap shop towel around fitting to absorb leakage). Place gauge bleed hose into container. Open bleed valve to release pressure.

ENGINE

Note. On Beretta and Corsica, remove engine and transaxle as an assembly from bottom of vehicle.

1. Release fuel system pressure. See «FUEL PRESSURE RELEASE»(/buick/century/v-1982-1996/remont/mechanical/#31l-v6-vins-mt__fuel-pressure-release) . Remove hood. Remove air cleaner and ducts. Disconnect battery cables. Drain coolant.
2. With transaxle in Neutral, remove torque strut-to-engine bracket bolts and position struts aside. Install right torque strut bolt into bracket. Using pry bar on installed bolt and bracket, rotate engine forward. Align hole in left torque strut bracket with slave hole in torque strut. Install left torque strut bolt to retain engine in forward position.
3. Disconnect necessary electrical connectors (except those on main engine harness) and fuel lines. Disconnect brake vacuum hoses at throttle body and brake booster. Disconnect control cables from throttle body. Disconnect secondary air injection pump (if equipped) and position aside. Remove left torque strut bolt and allow engine to rotate back to previous position.
4. Remove exhaust crossover pipe, serpentine drive belt and radiator hoses. Remove A/C compressor and power steering pump with hoses attached, and position them aside. Disconnect heater hoses from engine.
5. Raise and support vehicle. Remove flexplate/flywheel cover and starter. Remove torque converter bolts (A/T models). Remove transaxle bracket, engine front mount nuts and exhaust downpipe. Lower vehicle.
6. Support transaxle. Remove transaxle-to-engine bolts. Attach engine hoist, and remove engine. To install, reverse removal procedure. Fill cooling system.

Scheme 13

Scheme 14

1. Release fuel system pressure. See «FUEL PRESSURE RELEASE»(/buick/century/v-1982-1996/remont/mechanical/#31l-v6-vins-mt__fuel-pressure-release). Remove air cleaner assembly. Disconnect negative battery cable. Remove engine struts from strut bracket.
2. Disconnect control cables from throttle body. Disconnect brake booster vacuum pipe from upper intake manifold. Remove control cable bracket from upper intake manifold. Disconnect air intake duct from throttle body.
3. Remove throttle body from upper intake manifold. Remove EGR valve. Remove spark plug wiring harness from upper intake manifold. Remove upper intake manifold and gaskets. (Scheme 13)or (Scheme 14). Disconnect fuel lines from fuel rail. Remove serpentine drive belt and alternator.
4. Remove power steering hose bracket from alternator bracket. Remove power steering pump with hoses attached, and position it aside. Disconnect fuel injector connectors. Remove fuel rail. Remove spark plug wiring harness from lower intake manifold.
5. Drain cooling system. Disconnect heater hoses from engine. Remove left valve cover. Remove PCV hose and alternator brackets. Remove right valve cover. Remove upper radiator hose. Disconnect necessary electrical connectors.
6. Remove coolant temperature sensor. Remove necessary fuel lines. Remove throttle body heater hose. Remove heater hose from lower intake manifold. Remove lower intake manifold bolts, maintaining Belleville washers in same orientation on 4 center bolts. Remove lower intake manifold.
7. Loosen rocker arm nuts. Rotate rocker arms to one side and remove push rods. Note push rod location for installation reference (push rod lengths differ). Remove lower intake manifold gasket.

Installation

1. Apply bead of RTV sealant to front and rear ridges of cylinder block sealing surfaces. Install NEW intake manifold gaskets on cylinder heads. Ensure all holes are aligned.
2. Install push rods and rocker arms in original locations. Intake push rods are shortest and are marked Orange. Exhaust push rods are longest and are marked Blue.
3. On vehicles with VIN "M", install NEW lower intake manifold gaskets and manifold. Using a crisscross pattern, tighten lower intake manifold vertical bolts to specification, then tighten lower intake manifold diagonal bolts to specification. (Scheme 13) Install NEW upper intake manifold gaskets and manifold. Using crisscross pattern, tighten upper intake manifold bolts to specification. See «TORQUE SPECIFICATIONS»(/buick/century/v-1982-1996/remont/mechanical/#31l-v6-vins-mt__torque-specifications).
4. On vehicles with VIN "T", install NEW lower intake manifold gaskets and manifold. Tighten lower intake manifold bolts in sequence to specification. Install New upper intake manifold gaskets and manifold. Tighten upper intake manifold bolts in sequence to specification. (Scheme 14) See «TORQUE SPECIFICATIONS»(/buick/century/v-1982-1996/remont/mechanical/#31l-v6-vins-mt__torque-specifications).
5. To complete installation, reverse removal procedure. Use NEW "O" rings for fuel system components. Fill cooling system.

Removal

1. Remove air cleaner assembly. Disconnect negative battery cable. Remove serpentine drive belt. Remove A/C compressor with hoses attached, and position it aside.
2. Remove right engine-to-body torque strut rod. Remove A/C and torque strut bracket from engine. Remove heat shield. Disconnect exhaust crossover pipe from manifold. Disconnect exhaust downpipe from manifold. Remove exhaust manifold and gasket.

Reverse removal procedure using NEW gasket. Tighten exhaust manifold bolts to specification. See TORQUE SPECIFICATIONS .

1. Remove air cleaner assembly. Disconnect negative battery cable. Raise and support vehicle. Disconnect exhaust pipe from manifold. Lower vehicle. On Cutlass Supreme, Grand Prix, Lumina and Regal, remove engine-to-body torque strut rod and rotate engine as necessary to allow working space. See «ENGINE»(/buick/century/v-1982-1996/remont/mechanical/#31l-v6-vins-mt__engine) .
2. On all models, remove exhaust heat shield. Disconnect exhaust crossover pipe from manifold. Disconnect control cables and bracket from throttle body and upper intake manifold. Disconnect oxygen sensor connector. Remove exhaust manifold and gasket.

To install, reverse removal procedure using NEW gasket. Tighten exhaust manifold bolts to specification. See TORQUE SPECIFICATIONS .

1. Release fuel system pressure. See «FUEL PRESSURE RELEASE»(/buick/century/v-1982-1996/remont/mechanical/#31l-v6-vins-mt__fuel-pressure-release) . Disconnect negative battery cable. Remove intake manifold and gasket. See «INTAKE MANIFOLD»(/buick/century/v-1982-1996/remont/mechanical/#31l-v6-vins-mt) .
2. Remove exhaust crossover pipe. Raise and support vehicle. Remove oil filter and adapter. Position oil cooler aside (if equipped). Lower vehicle. Remove A/C compressor and position aside.
3. Remove radiator hose from water pump. Remove engine strut bracket bolts and bracket. Remove left side spark plug wires. Remove left exhaust manifold. See «EXHAUST MANIFOLD (LEFT)»(/buick/century/v-1982-1996/remont/mechanical/#31l-v6-vins-mt) . Remove vacuum pipe nut. Remove cylinder head bolts, head and gasket.

Inspection

Measure cylinder head surface warpage. Machine surface if warpage exceeds .005" (.13 mm). DO NOT remove more than .010" (.25 mm) of material from original surface.

1. Clean cylinder head bolt threads and cylinder block holes. Install gasket on cylinder block with THIS SIDE UP mark up (if equipped). Ensure all holes align with cylinder block.
2. Install cylinder head. Apply GM Sealant (1052080) to head bolt threads, and install bolts. Tighten cylinder head bolts in sequence to 33 ft. lbs. (45 N.m). (Scheme 15) Tighten bolts in sequence an additional 90 degrees using Cylinder Head Bolt Wrench (J-36660).
3. Install push rods. Intake push rods for VIN "M" are 5 3/4" long and marked Red. Intake push rods for VIN "T" are 6" long and marked Orange. Exhaust push rods are 6 3/8" long and marked Blue. To complete installation, reverse removal procedure. Tighten nuts and bolts to specification. See «TORQUE SPECIFICATIONS»(/buick/century/v-1982-1996/remont/mechanical/#31l-v6-vins-mt__torque-specifications). Fill cooling system.

Scheme 15

1. Release fuel system pressure. See «FUEL PRESSURE RELEASE»(/buick/century/v-1982-1996/remont/mechanical/#31l-v6-vins-mt__fuel-pressure-release) . Disconnect negative battery cable. Remove intake manifold and gasket. See «INTAKE MANIFOLD»(/buick/century/v-1982-1996/remont/mechanical/#31l-v6-vins-mt) .
2. Raise and support vehicle. Remove exhaust pipe at rear exhaust manifold. Lower vehicle. Disconnect exhaust crossover pipe at right exhaust manifold. Rotate engine forward. See «ENGINE»(/buick/century/v-1982-1996/remont/mechanical/#31l-v6-vins-mt__engine) . Disconnect secondary air injection pipe (if equipped). Disconnect oxygen sensor connector. Remove cylinder head bolts, head and gasket.

Measure cylinder head surface warpage. Machine surface if warpage exceeds .005" (.13 mm). DO NOT remove more than .010" (.25 mm) of material from original surface.

1. Clean cylinder head bolt threads and cylinder block holes. Install gasket on cylinder block with THIS SIDE UP mark up (if equipped). Ensure all holes align with cylinder block.
2. Install cylinder head. Apply GM Sealant (1052080) to head bolt threads, and install bolts. Tighten cylinder head bolts in sequence to 33 ft. lbs. (45 N.m). (Scheme 15) Tighten bolts in sequence an additional 90 degrees using Cylinder Head Bolt Wrench (J-36660).
3. Install push rods. Intake push rods for VIN "M" are 5 3/4" long and marked Red. Intake push rods for VIN "T" are 6" long and marked Orange. Exhaust push rods are 6 3/8" long and are marked Blue. To complete installation, reverse removal procedure. Tighten nuts and bolts to specification. See «TORQUE SPECIFICATIONS»(/buick/century/v-1982-1996/remont/mechanical/#31l-v6-vins-mt__torque-specifications). Fill cooling system.

1. Remove air cleaner. Disconnect negative battery cable. Drain cooling system. Remove belt tensioner and alternator. Remove power steering pump and position aside.
2. Remove radiator hose at water pump. Remove heater hose at thermostat by-pass pipe. Remove thermostat by-pass pipe from front cover. Remove crankshaft balancer.
3. Raise and support vehicle. Remove starter. Remove oil pan. See «OIL PAN»(/buick/century/v-1982-1996/remont/mechanical/#31l-v6-vins-mt) . Lower vehicle. Remove front cover bolts and cover.

1. Apply RTV sealant to sealing surface of front cover. Install NEW front cover oil seal. See «FRONT COVER OIL SEAL»(/buick/century/v-1982-1996/remont/mechanical/#31l-v6-vins-mt) . Apply RTV sealant to keyway in crankshaft and crankshaft damper.
2. Install crankshaft damper using Damper Installer (J-29113). Ensure damper installer threads are at least .20" (5.1 mm) into crankshaft. To complete installation, reverse removal procedure.

1. Remove air cleaner. Disconnect negative battery cable. Remove serpentine drive belt. Raise and support vehicle. Remove right front wheel and inner fender splash shield. Remove drive belt pulley.
2. Remove flexplate/flywheel cover. Prevent crankshaft from turning, and remove crankshaft damper bolt. Remove crankshaft damper using puller. Remove crankshaft damper key. Pry seal from front timing case cover.

Lubricate seal with engine oil. Install seal with open end of seal toward engine using Seal Installer (J-35468). To complete installation, reverse removal procedure.

1. Remove engine front cover. See «FRONT COVER»(/buick/century/v-1982-1996/remont/mechanical/#31l-v6-vins-mt). Place No. 1 piston at TDC with marks of camshaft and crankshaft sprockets aligned. (Scheme 16) NOTE: If camshaft sprocket does not come off easily, lightly strike lower edge of sprocket using a plastic mallet.
2. Remove camshaft sprocket bolts. Remove camshaft sprocket and timing chain. Using Crankshaft Sprocket Remover (J-5825-A), remove crankshaft sprocket.

Scheme 16

1. Install crankshaft sprocket (if removed). Apply assembly lube to camshaft sprocket thrust face. Install timing chain over camshaft sprocket. Hold sprocket vertically with chain hanging down. Align timing marks. (Scheme 16)
2. Install timing chain and camshaft sprocket on camshaft. Ensure sprocket dowel pin hole aligns with camshaft dowel pin. Install camshaft sprocket. Ensure timing marks are aligned. Lubricate timing chain with engine oil. Install front cover. See «FRONT COVER»(/buick/century/v-1982-1996/remont/mechanical/#31l-v6-vins-mt). To complete installation, reverse removal procedure. Tighten nuts and bolts to specification. See «TORQUE SPECIFICATIONS»(/buick/century/v-1982-1996/remont/mechanical/#31l-v6-vins-mt__torque-specifications).

1. Remove engine from vehicle. See «ENGINE»(/buick/century/v-1982-1996/remont/mechanical/#31l-v6-vins-mt__engine) . Remove intake manifold. See «INTAKE MANIFOLD»(/buick/century/v-1982-1996/remont/mechanical/#31l-v6-vins-mt) . NOTE: Mark locations of rocker arm components, push rods and valve lifters for installation reference.
2. Remove rocker arms, push rods and valve lifters. Mark component locations for installation reference. Remove front cover. See «FRONT COVER»(/buick/century/v-1982-1996/remont/mechanical/#31l-v6-vins-mt) .
3. Remove timing chain and camshaft sprocket. See «TIMING CHAIN»(/buick/century/v-1982-1996/remont/mechanical/#31l-v6-vins-mt) . Remove camshaft. If necessary, remove camshaft bearings using Remover/Installer (J-33049).

Inspect camshaft journal diameter, lobe lift and oil clearance. See CAMSHAFT SPECIFICATIONS table under ENGINE SPECIFICATIONS. Replace components if not within specification.

1. Install camshaft bearings (if removed). Ensure oil holes are aligned. Lubricate camshaft bearings and lobes with engine oil. If replacing camshaft, coat lobes with Prelube (1052365).
2. Install camshaft. To complete installation, reverse removal procedure. Ensure timing marks are aligned. Tighten nuts and bolts to specification. See «TORQUE SPECIFICATIONS»(/buick/century/v-1982-1996/remont/mechanical/#31l-v6-vins-mt__torque-specifications) .

1. Remove transmission. See information in appropriate AUTOMATIC TRANSMISSION REMOVAL & INSTALLATION article (A/T models) or FWD CLUTCHES (M/T models).
2. On M/T models, mark clutch pressure plate and flywheel for installation reference. Remove pressure plate, clutch disc and flywheel. On A/T models, remove flexplate and retainer.
3. On all models, pry seal from housing. Use care not to damage crankshaft at sealing surface. Note direction of seal installation.

1. Coat inner and outer seal surfaces with engine oil. Install seal on mandrel of Seal Installer (J-34686) until dust lip bottoms against seal installer collar. (Scheme 17)
2. Align seal installer dowel pin with alignment hole of crankshaft. Install seal installer on crankshaft. To install seal in seal bore, tighten seal installer handle until seal installer collar is even with cylinder block.
3. To complete installation, reverse removal procedure. Align reference marks on pressure plate and flywheel (M/T models). Tighten bolts to specification. See «TORQUE SPECIFICATIONS»(/buick/century/v-1982-1996/remont/mechanical/#31l-v6-vins-mt__torque-specifications).

Scheme 17

Note. Thermostat is located between engine block and coolant outlet assembly.

Disconnect negative battery terminal. Drain coolant until level is below thermostat. Remove air cleaner assembly and surge tank hose from coolant outlet. Remove coolant outlet to inlet manifold bolt and nut. Remove coolant outlet. Remove thermostat. (Scheme 18) To install, reverse removal procedure. Refill coolant.

Scheme 18

Disconnect negative battery cable. Drain cooling system. Remove air cleaner (if necessary), serpentine belt and water pump pulley. Note position of locator tab on top of water pump for installation reference. Remove water pump bolts, pump and gasket.

Apply thread sealant to water pump bolts. Install water pump using NEW gasket. Ensure locator tab on top of water pump housing is positioned vertically. Tighten bolts to specification. See TORQUE SPECIFICATIONS . To complete installation, reverse removal procedure. Fill cooling system.

1. Disconnect negative battery cable. Remove air cleaner assembly. Remove serpentine drive belt and tensioner. Support engine from top using Engine Support (J-28467-A) and Adapter Leg (J-36462).
2. Raise and support vehicle. Drain crankcase oil. Remove right wheel and splash shield. Remove steering gear pinch bolt. Remove transaxle mount nuts. Remove engine mount nuts. Remove front engine mount bracket from cylinder block.
3. Remove plastic and metal shields from starter area. Remove starter with wires connected, and position it aside. Place support under center of front frame crossmember. Loosen, but DO NOT remove, rear crossmember frame bolts.
4. Remove front frame bolts. Lower front frame.
5. Disconnect secondary air injection pipe (if equipped) from oil pan. For VIN "T", remove oil pan bottom nuts and bolts. For VIN "M", remove 2 side bolts and all bottom bolts. Remove oil pan and gasket.

1. Apply RTV sealant to oil pan gasket tabs that insert into gasket groove of outer surface on rear main bearing cap. Install oil pan using NEW gasket.
2. For VIN "M", install 2 oil pan side bolts to main bearing caps and tighten to specification. See «TORQUE SPECIFICATIONS»(/buick/century/v-1982-1996/remont/mechanical/#31l-v6-vins-mt__torque-specifications) . Install all bottom oil pan bolts and tighten to specification. For VIN "T", install all oil pan nuts and bolts and tighten to specification. To complete installation, reverse removal procedure. Fill crankcase.

Cylinder Head

Measure cylinder head warpage at deck surface. Resurface cylinder head if warpage exceeds .005" (.13 mm). DO NOT remove more than .010" (.25 mm) of material from original surface of cylinder head.

Valve Springs

Measure valve spring free length, out-of-square, pressure and installed height. See VALVES & VALVE SPRINGS SPECIFICATIONS table under ENGINE SPECIFICATIONS. Replace spring if not as specified.

Valve Stem Oil Seals

If oversize valves are installed, use oversize seals. Ensure seal is fully seated on guide. Intake and exhaust seals are different.

Valve Guides

DO NOT knurl valve guides. If valve stem oil clearance is not within specification, ream valve guides for oversize valve. See CYLINDER HEAD SPECIFICATIONS table under ENGINE SPECIFICATIONS.

Valve Seat

Measure seat runout and width. See CYLINDER HEAD SPECIFICATIONS table under ENGINE SPECIFICATIONS. Machine or replace valve seat as necessary if it is not within specification. Valve seat replacement procedure is not available from manufacturer.

Note. If valves and seats are reconditioned, install adjustable rocker arm studs.

Valves

Measure valve stem-to-guide oil clearance. See CYLINDER HEAD SPECIFICATIONS table under ENGINE SPECIFICATIONS. If valve margin is not within specification, machine or replace valve. If valve stem-to-guide oil clearance is not within specification, replace valve with oversize valve.

Valve Seat Correction Angles

If seat contact is too low (too close to stem) or too wide, use a 70-degree stone to raise and narrow seat.

CYLINDER BLOCK ASSEMBLY

Piston & Rod Assembly

Mark piston with cylinder number for installation in original location. Replace rod if bend or twist exceeds specification. See CONNECTING RODS SPECIFICATIONS table under ENGINE SPECIFICATIONS. Install piston with arrow on top of piston toward front of engine.

Fitting Pistons

1. Measure cylinder bore diameter at top and center of bore. Measure piston diameter at 90-degree angle to piston pin bore and 1/4" below center line of piston pin bore.
2. If piston clearance is not within specification, machine cylinder bore and install oversize piston as necessary. DO NOT machine oversize piston to fit cylinder bore or engine balance will be affected. See «PISTONS, PINS & RINGS SPECIFICATIONS»(/buick/century/v-1982-1996/remont/mechanical/#31l-v6-vins-mt) table under ENGINE SPECIFICATIONS.

Piston Rings

1. Measure piston ring end gap and side clearance. If end gap and side clearance are not within specification, replace piston rings and/or piston as necessary. See «PISTONS, PINS & RINGS SPECIFICATIONS»(/buick/century/v-1982-1996/remont/mechanical/#31l-v6-vins-mt) table under ENGINE SPECIFICATIONS.
2. Install piston rings with identification mark on ring land facing top of piston. Properly position ring end gaps around circumference of piston. (Scheme 19)

Scheme 19

Rod Bearings

Measure rod bearing oil clearance. If oil clearance is not within specification, regrind crankshaft and replace bearings. See CRANKSHAFT, MAIN & CONNECTING ROD BEARINGS SPECIFICATIONS table under ENGINE SPECIFICATIONS.

Crankshaft & Main Bearings

Measure crankshaft main bearing oil clearance, out-of-round and taper. If measurements are not within specification, regrind crankshaft and replace bearings. See CRANKSHAFT, MAIN & CONNECTING ROD BEARINGS SPECIFICATIONS table under ENGINE SPECIFICATIONS.

Thrust Bearing

Measure crankshaft end play (thrust bearing clearance). See CRANKSHAFT, MAIN & CONNECTING ROD BEARINGS SPECIFICATIONS table under ENGINE SPECIFICATIONS. If not within specification, replace bearing and/or repair or replace crankshaft.

Cylinder Block

Measure deck surface warpage. Machine surface if warpage exceeds .005" (.13 mm). DO NOT remove more than .010" (.25 mm) of material from original deck surface.

Valve Lifter Bores

Oversize valve lifters are available. If oversize lifters are installed, stamp oversize on cylinder block near lifter bore to indicate oversize lifters have been installed.

ENGINE OILING SYSTEM

A camshaft-driven, gear-type oil pump provides pressurized lubrication through oil filter to main gallery above left side of camshaft center line. (Scheme 20) This gallery provides lubrication to valve lifters on left bank, camshaft bearings, crankshaft and right gallery.

Right gallery supplies oil to valve lifters on right bank. Rocker arms are lubricated by passages in push rods. Slot in front camshaft bearing provides lubrication to camshaft sprocket thrust face. Pressure regulator valve is mounted in oil pump body.

Crankcase Capacity

Engine oil capacity is about 4 qts. (3.8L) without filter change. More oil may be necessary when replacing oil filter.

Oil Pressure

Minimum allowable oil pressure is 15 psi (1 kg/cm 2 ) at 1100 RPM.

Scheme 20

Removal & Disassembly

1. Remove oil pan. See «OIL PAN»(/buick/century/v-1982-1996/remont/mechanical/#31l-v6-vins-mt) under REMOVAL & INSTALLATION. Remove oil pump bolt, oil pump and extension shaft from rear main bearing cap.
2. To disassemble, remove pump cover. DO NOT remove pick-up tube from cover unless loose or broken. If pick-up tube is loose, bent or has been removed, replace pick-up tube and pump cover. WARNING: On some models, pressure regulator valve spring is under pressure. To prevent personal injury, use care when removing spring.
3. Remove gears from pump body. Remove pressure regulator valve cotter pin. Remove valve and spring.

1. Inspect components for damage. Using straightedge and feeler gauge, measure gear end clearance. Measure housing pocket depth and diameter. Measure gear diameter and length (thickness). Measure side clearance between gear tooth and housing.
2. Measure gear lash clearance between gear teeth. Check clearance between pressure regulator valve and bore. Replace components or pump assembly if not within specification. See appropriate OIL PUMP SPECIFICATIONS table.

OIL PUMP SPECIFICATIONS

OIL PUMP SPECIFICATIONS

Note. Use only original equipment gaskets for oil pump service, as gasket thickness is critical.

1. To reassemble, coat all components with engine oil. Reverse disassembly procedure using NEW pump cover gasket.
2. If installing new pick-up tube, apply Sealant (1050026) to pick-up tube. Install pick-up tube into pump cover using Suction Pipe Installer (J-21882) and plastic hammer.
3. To complete installation, reverse removal procedure. Ensure pump extension shaft is fully engaged. Tighten oil pump bolt to specification. See «TORQUE SPECIFICATIONS»(/buick/century/v-1982-1996/remont/mechanical/#31l-v6-vins-mt__torque-specifications) .

TORQUE SPECIFICATIONS

TORQUE SPECIFICATIONS

ENGINE SPECIFICATIONS

GENERAL ENGINE SPECIFICATIONS

CRANKSHAFT, MAIN & CONNECTING ROD BEARINGS SPECIFICATIONS

CONNECTING RODS SPECIFICATIONS

PISTONS, PINS & RINGS SPECIFICATIONS

CYLINDER BLOCK SPECIFICATIONS

VALVES & VALVE SPRINGS SPECIFICATIONS

CYLINDER HEAD SPECIFICATIONS

CAMSHAFT SPECIFICATIONS

See also:
• ENGINE OVERHAUL PROCEDURES - GENERAL INFORMATION
• COMPUTER RELEARN PROCEDURES
• FUEL PRESSURE RELEASE
• TORQUE SPECIFICATIONS
• ENGINE
• INTAKE MANIFOLD