Timing Belt Interference Caution Note: Camshaft

Carmax 6067 170 Turnpike Rd Westborough, MA 01581

YMMS: 1991 Chevrolet Lumina Z34

Sep 3, 2020

License: Odometer:
Engine: 3.4L Eng VIN:

TIMING BELT INTERFERENCE CAUTION

NOTE: CAMSHAFT DRIVE BELTS OR TIMING BELTS -

The condition of camshaft drive belts should always be checked on vehicles which have more than 50,000 miles. Although some manufacturers do not recommend replacement at a specified mileage, others require it at 60,000-100,000 miles. A camshaft drive belt failure may cause extensive damage to internal engine components on most engines, although some designs do not allow piston-to-valve contact. These designs are often called "Free Wheeling". Many manufacturers changed their maintenance and warranty schedules in the mid-1980's to reflect timing belt inspection and/or replacement at 50,000- 60,000 miles. Most service interval schedules shown in this section reflect these changes. Belts or components should be inspected and replaced if any of the following conditions exist:

Crack Or Tears In Belt Surface Missing, Damaged, Cracked Or Rounded Teeth Oil Contamination Damaged Or Faulty Tensioners Incorrect Tension Adjustment

REMOVAL & INSTALLATION

Tip: Timing belt

CAUTION: For 1996-97 models, this application is an interference engine. Do not rotate camshaft or crankshaft when timing belt is removed, or engine damage may occur.

NOTE: The camshaft timing procedure has been updated by TSB bulletin No. 47-61-34, dated December, 1994.

REMOVAL

Tip: timing 3.4 x motor
1. Disconnect negative battery cable. Remove air cleaner and duct assembly. Drain engine coolant. 2. Remove accelerator and cruise control cables from throttle body. Remove fuel rail cover. Relieve fuel pressure. Remove fuel lines from fuel rail. Remove fuel mounting bracket.

3. Remove heater hose and bracket from lower intake manifold. Remove PCV valve and vacuum line from throttle body. Remove electrical connectors from EGR valve, canister purge solenoid and MAP sensor. Remove EGR valve, and position aside. Remove vacuum lines from upper intake manifold tee.

4. Remove wiring loom bracket for rear spark plug wires. Remove upper intake manifold. Remove coolant recovery tank. Remove serpentine drive belt and drive belt tensioner.

5. Siphon fluid from power steering pump. Disconnect power steering lines and remove power steering pump.

6. On 1991-93 vehicles only, reposition Powertrain Control Module (PCM) out of way. Remove PCM mounting bracket. On 1994-95 vehicles only, disconnect PCM connectors and secure out of way.

7. On all vehicles, note position for reassembly reference and remove spark plug wires from spark plugs. Remove wiring harness cover at right side (passenger) strut tower. Remove fuel line bracket.

8. Remove timing belt covers. Remove breather hose from rear camshaft cover and crankcase vent from breather manifold. Remove camshaft carrier covers.

9. Remove side plate bolts securing timing belt tensioner actuator. Rotate actuator assembly from tensioner pulley socket and out of mounting base. Remove timing belt tensioner pulley. See Fig 1.

NOTE: Actuator assembly uses a tapered bushing between the actuator and mounting base. DO NOT lose or damage the bushing when removing the actuator assembly.

10. Position timing belt tensioner actuator in vise with rod tip (rubber boot end) pointing down. 11. Straighten out a standard paper clip (.032" with no serrations) and form a loop at one end. See Fig 2.
Remove rubber end plug from rear of tensioner actuator. Push paper clip through end of vent plug and into pilot hole. Insert a small screwdriver into the screw slot inside actuator, behind rubber end plug.

CAUTION: Allow oil to flow towards boot end of actuator for at least 5 minutes prior to refilling.

NOTE: Tensioner actuator is oil filled. Removal of plug may allow oil to escape. DO NOT remove vent plug.

12. Retract actuator plunger by rotating screw in a clockwise direction until it is fully retracted. Push on paper clip and slowly rotate screw counterclockwise until paper clip engages. Remove timing belt.

13. Rotate crankshaft so that No. 1 cylinder is at TDC of compression stroke. Mark the timing indicator with White paint or equivalent on the crankshaft balancer and front cover. See Fig 3.

NOTE: Remove timing marks from camshaft and intermediate shaft sprockets.

14. Position camshafts so that flat spots are "UP" for installation of Camshaft Hold-Down Tools (J 38613-
A). Install Camshaft Hold-Down Tools (J 38613-A) on both camshaft carriers. See Fig 4.

15. Remove camshaft sprocket center bolts. Note difference between early and late designs. See Fig 5.
Lightly tap on rear of sprockets to remove from camshaft.
Fig 1: Identifying Timing Belt Assembly Components

Courtesy of GENERAL MOTORS CORP.

Fig 2: Reworking Paper Clip

Fig 3: Aligning Timing Marks

Fig 4: Installing Camshaft Hold-Down Tools (J 38613-A)

Fig 5: Identifying Camshaft Timing Sprocket Designs

INSPECTION

1. To determine if timing belt length is within specifications, measure tensioner actuator from centerline of tensioner actuator to end of rubber boot. See Fig 6. If measurement is 3.2-3.7" (80.5-94.0 mm) for a used belt, the belt is in acceptable range. Replace belt is measurement is more than 3.7" (94 mm).

2. Inspect belt teeth and back side of belt for cracks, tears or other damage. Inspect components for excessive wear or unusual conditions. Note any evidence of oil or other fluid intrusion.
Fig 6: Measuring Timing Belt Tensioner Actuator Length

INSTALLATION

1. Install camshaft sprockets with bolts and locks. Tighten bolts finger tight. Install timing belt onto camshaft sprockets in a counterclockwise direction. Continue installing timing belt, making sure timing belt teeth are fully engaged with all sprockets.

2. Install timing belt tensioner pulley. Tighten timing belt tensioner pulley bolt to 37 ft. lbs. (50 N.m). 3. Install rubber end plug in rear of tensioner assembly until flush. Ensure plug is sealed against case.

NOTE: If tensioner oil has been lost, fill tensioner with
Mobil 1 SAE 5W-30 synthetic engine oii through plug hole. Fill to bottom of plug hole only when plunger is fully retracted and pin is installed.

4. Install actuator bushing into side plate. Install timing belt actuator and actuator side plate. Tighten side plate bolt to 20 ft. lbs. (27 N.m).

NOTE: Ensure actuator bushings and appropriate holes in side plate are clean. DO NOT lubricate bushings.

5. Rotate pulley assembly into timing belt a maximum of 11 ft. lbs. (15 N.m) to allow engagement of actuator shaft into pulley pocket arm socket. Pull the paper clip from the actuator. Retighten pulley assembly 11 ft. lbs. (15 N.m) counterclockwise to seat pulley into belt.

6. Tighten both right hand camshaft sprockets (bank closest to firewall) to 96 ft. lbs. (130 N.m). Remove camshaft hold-down from righthand camshaft carrier.

7. Rotate crankshaft one full turn (360 degrees) clockwise, as viewed from front of engine. Align crankshaft reference marks. See Fig 3. Make sure both righthand camshaft flat spots are down. Tighten both lefthand camshaft sprockets (bank closest to radiator) to 96 ft. lbs. (130 N.m). Remove camshaft hold-down from lefthand camshaft carrier.

8. Rotate engine clockwise (as viewed from front) 2 times to seat belt and verify correct valve timing.
DO NOT reverse rotation. Make sure both camshaft flat spots are up on one bank and down on opposing bank.

9. Install camshaft carrier covers. Install breather hose and crankcase vent onto rear cover. Install timing belt covers.

10. To complete installation, reverse removal procedure. Refill cooling system with 50/50 mix of water and coolant. Open air bleed valve on thermostat housing while filling cooling system. Adjust drive belts to proper tension.

TIMING BELT & CAMSHAFT TIMING PROCEDURE

CAUTION: If a valve timing related problem is caused by a slipped belt, always replace belt. If timing belt is to be removed, the "painted on" timing marks on the cam gears are no longer valid and must be removed.

NOTE: For reference, left bank is front bank, and right bank is rear bank.

NOTE: Tools required: Cam Hold Down (J-38613-A),
Camshaft Sprocket Holding Tool (J-38614) and Torque Angle Meter (J-36660-A).

Removal

Tip: timing 3.4 x motor

NOTE: The camshaft timing procedure has been updated by TSB bulletin No. 47-61-34, dated December, 1994. Before

proceeding, see SECTION 6A9 - REVISED CAMSHAFT TIMING PROCEDURE for possible updated information.

For belt measurement specification, see TIMING BELT TENSION SPECIFICATIONS. TIMING BELT TENSION SPECIFICATIONS

Application

In. (mm)

Tensioner Measurement

New Belt

3.2-3.5 (80.5-89.0)

3.2-3.7 (80.5-94.0)

Used Belt

1. Disconnect negative battery cable. Remove air cleaner duct. Drain engine coolant. See COOLING
SYSTEM DRAINING. Disconnect accelerator and cruise control cables from throttle body. Remove the fuel injector sight shield. Remove fuel rail cover and relieve fuel pressure. See FUEL PRESSURE RELEASE. Remove fuel lines from fuel rail and remove fuel mounting bracket.

2. Remove heater hose and bracket from lower intake manifold. Remove PCV valve and vacuum line from throttle body. Disconnect electrical connector from EGR. Remove EGR valve. Disconnect electrical connection from canister purge solenoid and MAP sensor. Remove vacuum lines from upper intake manifold tee. Remove wiring loom bracket for rear spark plug wires. Disconnect power brake vacuum hose and remove upper intake manifold support bracket and manifold. Remove coolant recovery tank.

3. Remove serpentine belt and belt tensioner. Remove power steering pump. Disconnect PCM electrical connectors and reposition. Disconnect spark plug wires from spark plugs. Relocate wiring harness cover at right strut tower. Remove fuel line bracket and all upper timing belt covers (3). Remove breather hose from rear camshaft cover, and crankcase vent from breather manifold.

4. Remove camshaft carrier covers. See CAMSHAFT CARRIER & COVERS. Remove side plate bolts from actuator and rotate actuator assembly from tensioner pulley socket, and out of mounting base. See Fig 8. Remove timing belt tensioner pulley. See Fig 8. DO NOT install the rod tip or the tensioner actuator boot in the jaws of a vise or damage to the assembly may occur.

5. Position actuator in vertical position (rod tip down), lightly clamp actuator body in vise. See Fig 10.
(Position the tensioner actuator up, so the oil goes to the boot end for at least 5 minutes before refilling the actuator prior to reassembly, if necessary). Actuator assembly uses a tapered bushing between actuator and mounting base. DO NOT lose or damage bushing when removing actuator assembly.

6. Straighten out a standard paper clip .032" (.81mm) diameter, to a minimum straight length of 1.85 "
(47 mm). Form a double loop in remaining end of paper clip. See Fig 12. Actuator assembly is filled with oil and removal of the plug may allow oil to escape. DO NOT remove vent plug. Push paper clip through center of vent plug and into pilot hole. Insert a small screwdriver into screw slot inside actuator, behind rubber end plug. Retract actuator plunger by rotating screw in a clockwise direction, until it is fully retracted. Push on paper clip and slowly rotate screw counterclockwise until paper clip engages. This unloads tensioner.

7. Remove timing belt. Rotate crankshaft so No. 1 cylinder is at TDC (Top Dead Center). Mark crankshaft timing indicator (with White paint or equivalent) on crankshaft balancer and front cover only. See Fig 9.

CAUTION: Remove the painted on factory timing marks from all 4 camshafts and the intermediate shaft sprocket (they will no longer be used for timing reference). Prior to installing the Cam Hold Down, ensure that the bolt hole is free of any debris or the camshaft carrier may be damaged.

8. Position camshafts so flat spots are UP for installation of Cam Hold Down. See Fig 14. Install Cam
Hold Downs on both camshaft carriers. One on left (front head) and the other on the right (rear head). To remove camshaft sprockets, install Cam Hold Down and remove bolts, taper lock rings, and sprockets by lightly tapping on it with a soft faced hammer. See Fig 13.

Installation

NOTE: The camshaft timing procedure has been updated by TSB bulletin No. 47-61-34, dated December, 1994. Before proceeding, see SECTION 6A9 - REVISED CAMSHAFT TIMING PROCEDURE for possible updated information.

NOTE: Tools required: Cam Hold Down (J-38613-A).

1. Install intermediate drive sprocket and all camshaft sprockets with taper lock rings FINGER TIGHT.
Install timing belt in a counterclockwise direction around sprockets. Ensure timing belt teeth are fully engaged with all sprockets. Tighten tensioner pulley bolt to specification. See TORQUE SPECIFICATIONS.

2. If actuator oil has been lost, fill actuator with SAE 5w30 Mobil 1 (or equivalent) synthetic engine oil through end hole. Fill to bottom of plug hole, only when actuator is fully retracted, and pin is installed. Install rubber end plug into rear of the actuator assembly, push until flush and snapped into place. Make sure end plug has sealed against the case. Inspect bushings and appropriate holes to make sure they are clean. Install actuator bushing into side plate. DO NOT lubricate.

3. Install timing belt actuator and actuator side plate. Torque to specification. Rotate pulley assembly into belt a maximum of 132 INCH lbs. (15 Nm.) to allow engagement of actuator shaft into pulley arm socket. Pull lock pin and discard. This releases tensioner. Torque tensioner pulley assembly to 132 INCH lbs. (15 Nm.) counterclockwise to seat pulley into belt. Tighten both right hand (rear bank) camshaft sprocket bolts to 96 ft. lbs. (130 Nm). Remove Cam Hold Down from right hand (rear bank) camshaft carrier. Rotate crankshaft 360 degrees clockwise while looking at front of engine and align crankshaft reference marks. Make sure both right hand (rear bank) camshaft flats are DOWN. Tighten both left hand (front bank) camshaft sprocket bolts to 96 ft. lbs. (130 Nm).

4. Remove Cam Hold Down from left hand (front bank) camshaft carrier. Rotate crankshaft 720 degrees clockwise while looking at front of engine to seat timing belt, and VERIFY correct timing by making sure both camshaft flatspots are UP on one bank, and DOWN on the opposing bank. See Fig 14.
5. Install camshaft carrier covers and bolts. Torque bolts to specification. Install breather hose from rear camshaft cover, and crankcase vent from breather manifold. Install timing belt covers and bolts. Tighten bolts to specification. Install fuel line bracket and bolt. Tighten bolt to specification. Install wiring harness cover at right strut tower.

6. Install spark plug wires. Install PCM electrical connectors. Install power steering lines to pump. Install serpentine belt and tensioner. Tighten serpentine belt tensioner bolt to specification. Install coolant recovery tank. Install upper intake manifold, bolts, and nuts. Tighten to specification. See TORQUE SPECIFICATIONS. Install power brake vacuum hose and wiring loom bracket for rear spark plug wires.

7. Install vacuum lines to upper intake manifold tee. Connect electrical connections to canister purge solenoid and map sensor. Install EGR valve and torque bolts to specification. Connect electrical connectors to EGR. Install PCV valve and vacuum line to throttle body. Install heater hose and bracket to lower intake manifold. Install fuel mounting bracket and bolt, tighten to specification. Connect fuel lines to fuel rail and install fuel rail cover. Connect accelerator and cruise control cables to throttle body. Install air cleaner assembly. Refill cooling system and bleed. See COOLING SYSTEM BLEEDING. Fill power steering system. Install negative battery cable.

Fig 7: Removing & Installing Timing Belt

Fig 8: Removing & Installing Timing Belt Actuator Pulley

Fig 9: Removing Factory Timing Marks

Fig 10: Measuring Timing Belt Tensioner Length

Fig 11: Installed View Of Timing Belt & Gears

Fig 12: Reworking Paper Clip

Fig 13: Identifying Cam Sprocket Timing Gears

Fig 14: Camshaft Flats Face UP On Both Banks For Installation Of J-38613-A. For Final Timing Reference, Camshaft Flats Are UP On One Bank & DOWN On Other.

TIMING CHAIN

Removal (Except Camaro & Firebird)

1. Drain cooling system. Disconnect negative battery cable. Remove coolant reservoir. Remove serpentine drive belt and tensioner. Remove power steering pump with hoses attached and lay aside. Raise and support vehicle.

2. Remove right front wheel and inner splash shield. Remove crankshaft belt pulley. Remove flexplate/flywheel cover. Prevent crankshaft from turning and remove crankshaft damper bolt. Remove crankshaft damper using puller.

3. Remove serpentine drive belt idler pulley. Remove oil pan. See OIL PAN. Disconnect radiator hose and coolant by-pass pipe from water pump. Disconnect canister purge hose. Remove front timing case cover.

4. Rotate crankshaft, aligning timing marks on camshaft and crankshaft sprockets. See Fig 15. Remove camshaft sprocket bolts. Remove camshaft sprocket and timing chain. Remove crankshaft sprocket (if necessary).

Installation (All Models)

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 downward. Align timing marks. See Fig 15.

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.

3. Apply Sealant (1052917) or RTV sealant to sealing surfaces of front timing case cover. Install front timing case cover and new gasket. If crankshaft seal is removed, lubricate new seal with engine oil and install with open side of seal toward engine using Seal Installer(J 35468 A).

4. Apply sealant to crankshaft and crankshaft damper keyways. Install crankshaft damper using Damper
Installer (J 29113). Ensure damper installer threads extend at least .20" (5.1 mm) into crankshaft.

5. To install remaining components, reverse removal procedure. Tighten retaining nuts and bolts to specification. Refer to the TORQUE SPECIFICATIONS table.

Fig 15: Aligning Timing Marks

TIMING CHAIN & SPROCKETS

Removal

1. Remove front cover. See FRONT COVER. Mark crankshaft and intermediate shaft sprockets in relation to timing chain for reassembly reference. See Fig 16. Remove timing chain tensioner bolts.

2. Raise and support vehicle. Remove timing chain and crankshaft sprocket using Universal Puller
Bridge (J-8433) and Legs/Protector (J-38611). If intermediate gear does not slide off easily with timing chain assembly, rotate crankshaft back and forth to help loosen gear. Remove timing chain tensioner.

Inspection

Inspect crankshaft alignment key for burrs or marks that could affect assembly. Repair or replace as necessary.

Installation

1. Ensure crankshaft key is installed and fully seated. Using Tensioner Retractor (J-33875), retract timing chain tensioner shoe and lock it in place with a cotter pin, rivet, or nail. See Fig 17.

2. Using upper hole as primary locator, install tensioner. Finger-tighten tensioner bolts. Tighten slotted bolt and then remaining bolts to specification. See TORQUE SPECIFICATIONS. Apply light coat of oil or lithium grease to chain contact surfaces of nylon pad and blade (if equipped).

3. Install chain and sprocket assembly, aligning marks made during removal. During installation, keep assembly aligned (parallel). See Fig 18. Intermediate shaft may move against rear cover. Ensure rubber and tension blade of tensioner do not become caught, misaligned or dislodged.

4. Large chamfer and counterbore on crankshaft sprocket must face engine. See Fig 16. Spline sockets on intermediate shaft sprocket must face engine.

5. Crankshaft sprocket must be pressed onto crankshaft for the last .31" (8 mm) using Sprocket Installer
(J-38612). Ensure timing is correct. Pull pin from tensioner. To complete installation, reverse removal procedure.
Fig 16: Identifying Timing Chain & Components

Fig 17: Retracting Timing Chain Tensioner Shoe

Fig 18: Aligning Timing Chain Assembly

CAMSHAFT TIMING BELT (3.4L V6)

The 3.4L V6 engine is equipped with a camshaft timing belt that should be inspected for cracks, wear or oiliness at 60,000 miles and every 15,000 miles thereafter. Check tensioner for proper operation. Replace belt or parts, as necessary.

CAUTION: Failure to replace a faulty camshaft timing belt may result in serious engine damage.

The condition of camshaft drive belts should always be checked on vehicles which have more than 50,000 miles. Although some manufacturers do not recommend belt replacement at a specified mileage, others require it at 60,000-100,000 miles. A camshaft drive belt failure may cause extensive damage to internal engine components on most engines, although some designs do not allow piston-to-valve contact. These designs are often called "Free Wheeling". Many manufacturers changed their maintenance and warranty schedules in the mid-1980's to reflect timing belt inspection and/or replacement at 50,000-60,000 miles. Most service interval schedules in this manual reflect these changes. Belts or components should be inspected and replaced if any of the following conditions exist:

Cracks Or Tears In Belt Surface Missing, Damaged, Cracked Or Rounded Teeth Oil Contamination Damaged Or Faulty Tensioners Incorrect Tension Adjustment

SERVICE INTERVALS & SPECIFICATIONS [ ENGINE CONTROLS - SPECIFICATIONS - 4-CYL : QUICK-SERVICE ]