Excessive Vehicle Noise and/or Vibration. Saturn Saturn 1994

For 1990-2009 cars

# Excessive Vehicle Noise and/or Vibration

Subject: | Excessive Vehicle Noise and/or Vibration (Check Powertrain Mounts, Exhaust, and/or Cooling System) Due to the following revisions, this bulletin supercedes bulletin 91-t-36A, which should be discarded.

Models: | 1991-1994 Saturns

### Condition

Some owners of 1991-1994 Saturns may comment on objectionable vehicle noise and/or vibration levels observed in the steering wheel, seat and/or floor pan.

### Cause

Objectionable vehicle noise and/or vibration may be caused by:

• | Preloaded powertrain mounts (1991 vehicles)

• | Preloaded engine strut cradle bracket or cradle misaligned to body (1992 -- 1994 vehicles)

• | Improperly positioned/worn exhaust system isolators and muffler band clamp/block (1991-1994 vehicles)

• | Lower cooling module grommets, improper positioning of wiring harness and upper cooling system module grommets (1991-1994 vehicles)

• | Improper routing of A/C hoses or deareation hoses, hood release cable and air inlet snorkel (1991 -- 1993 vehicles)

• | Debris in accessory drive belt pulleys (1991-1993 vehicles)

• | Improper adjustment of hood stop(s) (1991-1994 vehicles)

• | DOHC (LLO) automatic transaxle mount assembly replacement (1991 vehicles)

• | Malfunction of engine electrical/fuel system (1991-1994 vehicles)

### Correction

Before attempting repairs, please review the following vehicle noise and vibration information.

VEHICLE NOISE AND VIBRATION

Four -- cycle engines have a second -- order firing frequency. This means that it takes two, complete crankshaft revolutions to fire all cylinders or one crankshaft revolution to fire one -- half of the cylinders. Because of the way the cylinders are fired, an engine disturbance is created due to cylinder pressures or pulses. Most engine disturbances are absorbed by the powertrain rubber isolation mounts. Depending on isolation package, some of this disturbances may be transmitted into body structure and felt inside the vehicle when stopped, with the engine running and/or under certain driving conditions. These conditions are natural in most vehicles.

Vibrations are normally felt in steering wheel, lower seat cushion, seat back or floor pan. Vibrations are diagnosed with the vehicle stopped and transaxle in (D) Drive and/or (R) Reverse for automatic transaxles, and in Neutral for manual transaxles. If the vehicle is equipped with A/C the A/C should be On or Off depending on the instruction given in the diagnosis step.

Important: Important: Before performing the following procedures, the vehicle should be road tested and complaint verified with the engine at operating temperature. Engine misfire complaints are usually easy to detect during a short road test and must be corrected prior to evaluating a vibration and/or noise concern.

NOTE:

Minimum Idle Speed (TBI -- MFI) adjustments are set at the factory and MUST NOT be tampered with to alter minimum or maximum engine idle speed. Improper adjustment of the idle speed screw can cause false PCM codes, idle instability and automatic transaxle shift concerns, etc.

Perform the following steps in order to decrease vehicle noise and/or vibration.

PROCEDURE: NOTE: The following procedures are performed under three different conditions:

• | Vehicle on Hoist, Engine Off

• | Vehicle on Ground, Engine Off

• | Vehicle on Ground, Engine Running

### VEHICLE ON HOIST, ENGINE OFF

REAR TRANSAXLE MOUNT (1991 VEHICLES)

1. Loosen the front transaxle mount bolts and rear transaxle mount through -- bolt, and rock the powertrain to make sure that it is free. Tighten the front mount bolts .

Important: To access the front mount -- to--transaxle bolts, remove forward, lower left -- hand, wheel well splash shield push pins and remove the shield aside.

2. The rear transaxle mount bracket should now move vertically 6.35 - 12.70mm (1/4 - 1/2 in.) when measured at the mount through the bolt hole slot. NOTE: If the powertrain cannot be rocked, the powertrain is probably bound at the front transaxle mount. Refer to "Front Transaxle Mount" in this bulletin.

Important: A knocking or clicking sound can be emitted from either the transaxle front or rear mount. This noise, which frequently comes from the rear mount, is normally heard during acceleration, a sharp turn of the wheels, shifting gears, or initially letting out the clutch and under other normal operating conditions. The suspected mount attachment fastener torques must be checked. If the fastener torques are correct, the suspect mount must be replaced.

3. The rear transaxle mount through -- bolt should move freely in the bracket and mount. If the bracket has damaged by the bolt head/nut from previous adjustments, the rear transaxle mount must be replaced. Torque the nut using a box end wrench and a torque wrench.

Important: Do not pull vertically downward on the mount bolt/nut when tightening, as this will preload the mount's rubber insert.

4. Check the torque of the two rear transaxle mount - to- cradle bolts.

Important: The rear transaxle mount through - bolt and nut must be loosened and the powertrain rocked to adjust the mount when A/C option is installed. Refer to steps 1-4 of rear transaxle mount.

### FRONT TRANSAXLE MOUNT (1991- VEHICLES)

1. Check for front transaxle mount housing position, relative to the transaxle case. The mount housing must be both horizontally and vertically parallel with transaxle housing.

Important: The rubber insert must be flush, the mount is probably misaligned. The mount may have to be removed for inspection of debris on the cradle and/or housing under the mount assembly. A short, straight edge (such as a credit card) can be used to evaluate housing and rubber insert position.

2. To check and correct improperly positioned mount, perform the following procedures:

2.1. | Remove the two rearward, lower radiator splash shield pushpins and lower rear side of the shield.

2.2. | Check the front transaxle mount housing to make sure it is parallel with the rubber insert, horizontally and vertically as shown with arrows.

2.3. | If vertical alignment is not correct, remove the forward, lower left -- hand side wheelwell splash shield pushpin and move the shield aside for access to the front mount-to-transaxle bolts.

2.4. | Remove both cradle attachment nuts and the two bolts which attach the mount to the transaxle.

2.5. | Inspect the mount casting cradle surfaces for debris under the mount assembly. If the mount has to be removed, it can be checked with a 90 degree square on the side of a bench to make sure the cradle mounting and rubber insert casting surfaces are at a 90 degree angle.

2.6. | If the mount is not repairable, it must be replaced.

2.7. | If horizontal alignment is not correct, loosen both transaxle front mount-to-cradle attachments nuts 1/4 of a turn until the mount housing is parallel to the transaxle surface.

| Important: A large screwdriver can be wedged between the outer mount housing and the transaxle case keep the mount parallel with the transaxle case when tightening the nuts.

2.8. | Hold the mount in place and tighten the two nuts.

### FRONT ENGINE MOTION RESTRAINT CABLE AND MOTION RESTRICTOR (SLAP/SNAP) (1991 VEHICLES)

The large restraint cable located at the rearward side of the engine mount can make a squeaking noise during vehicle starts, stop, acceleration, etc. The cable can be lubricated with chassis grease to eliminate this noise.

The motion restrictor cable is only used on the DOHC (LLO) engine equipped with a manual transaxle. The cable is located at the right - hand, forward side of the engine. This cable is attached to the forward side of the engine block and cradle. If the motion restrictor emits a slapping or clicking noise during shifts or harsh accelerations, it must be replaced.

### ENGINE STRUT CRADLE BRACKET (1992 - 1994 VEHICLES)

Check the powertrain for binding and strut noises (squeaks) by pushing forward and rearward on the engine oil pan. The powertrain should travel a minimum of 3.18mm (1/8 in.).

If the powertrain does not move:

1. Check cradle - to - body alignment at the two front cradle alignment holes. Adjust cradle - to - body, only if necessary.
2. Check the struts (engine and transaxle) for correct installation and bushing wear.
3. Loosen the two engine strut bracket to cradle fasteners. Refer to "Engine Strut Cradle" section in the Powertrain Mounts Service Manual."
4. Shake the powertrain by pushing forward and rearward on the engine oil pan.
5. Allow the powertrain to settle to its natural position and tighten the two engine strut bracket to cradle fasteners.
6. If the strut noises cannot be eliminated during powertrain adjustment, replace the strut assembly.

graphic (no graphic #)

### INTERMEDIATE EXHAUST PIPE ISOLATOR (1991 VEHICLES)

The new intermediate exhaust pipe isolator can be installed on vehicles equipped with the old -- type intermediate exhaust pipe isolator to reduce interior vehicle noise, if the exhaust heat shield is modified (as shown in Figure). If the heat shield is not modified and the new intermediate exhaust pipe isolator is installed, the isolator will contact will contact the exhaust heat shield. To modify the exhaust heat shield and install new intermediate exhaust pipe isolator, refer to the following procedure.

Important: A new intermediate exhaust pipe isolator is released for all vehicles, built before MZ117347, except the SOHC (LKO) engine equipped with automatic transaxle, ALL SOHC (LKO) engines with an automatic transaxle, and all other vehicles built after VIN MZ117347, have the new intermediate exhaust pipe isolator installed during production (Figure, View B).

Caution: HEAVY WORK GLOVES AND EYE PROTECTION MUST BE WORN WHEN MODIFYING THE EXHAUST HEAT SHIELD, AND WHEN REMOVING AND INSTALLING THE INTERMEDIATE EXHAUST PIPE ISOLATOR. THE EXHAUST HEAT SHIELD EDGES ARE EXTREMELY SHARP AND CONTACT WITH THE EDGES COULD CAUSE PERSONAL INJURY.

1. Raise the vehicle on a hoist.
2. Remove the intermediate exhaust pipe bolt and isolator.
3. Using tin snips, vertically cut 25.4 mm (1 in.) of tin away from the end of the heat shield as shown in Figure. Shortening the heat shield behind the isolator allows the new (thicker) isolator room for forward and rearward movement.NOTE: The new isolator bolt is a smaller diameter then the original and must be used to secure the isolator to the exhaust pipe.
4. Install the new intermediate exhaust pipe isolator (P/N 21011418) and bolt (P/N 21011471). The new rubber isolator has to be held squarely in place when tightening the bolt or the isolator will become bound.

### CATALYTIC CONVERTER (1991 VEHICLES)

Inspect exhaust system isolators used at the catalytic converter. Verify that an interference fit exists between each body attachment hanger and isolator. Also, check to see if the attachment hole on the isolator is worn (shown) in Figure). If a loose fit exits or if the isolator attachment hole is worn, replace them with a new isolator (P/N 21011302). The isolator bolt will crush the rubber of the new hangers slightly to make sure they remain tight against the catalytic converter flange.

### MUFFLER (1991 - 1994 VEHICLES)

Verify that the muffler can be moved both vertically and horizontally in the isolator block a minimum of 1.60 mm (1/16 in.) vertically (direction "A", in Figure) and 3mm (1/8 in.) horizontally (direction "B", in Figure).

If the muffler does not move freely, perform the following steps.

1. Loosen the band clamp and position the muffler to allow the movement previously described.

Important: Two rows of bumps have been formed in the muffler sheet metal and the muffler clamp must be between them.

2. Tighten the band clamp. Check for proper muffler movement.

Important: If muffler movement cannot be obtained, the exhaust system will have to be carefully lowered and the muffler isolator block will have to be adjusted or shimmed. Washers, with an inside diameter of 9.53mm (3/8 in.), can be installed on the attachment bolts(s) between muffler block and frame rail to align the hanger parallel with the muffler.

3. To lower the exhaust system:

3.1. | Remove the intermediate exhaust pipe center isolator, muffler band clamp carefully lower the exhaust system.

3.2. | Loosen the muffler isolator block fasteners and inspect the isolator and body surfaces for debris.

3.3. | Clean the surfaces or rotate the block to align it with the muffler band insert. If necessary, install washers between the muffler and frame rail.

3.4. | Tighten he muffler block fasteners and band clamp. Check for proper muffler movement.

### MUFFLER (1992 EARLY PRODUCTION VEHICLES)

The exhaust system may contact the rear cross -- member (suspension), rear muffler heat shield or muffler isolator block during forward or reverse transaxle shifts.

Check the exhaust system pipe for contact with the rear suspension cross -- member and muffler band clamp for contact with the heat shield/isolator block. If the exhaust pipe or band clamp are contacting the cross -- member, heat shield or isolator block, the muffler band clamp will have to be positioned as follows:

1. Loosen the muffler band clamp.
2. Align the forward leading edge of the muffler band clamp with the front leading edge of the forward set of bumps on the muffler. This will position the forward leading edge of the band clamp on top of the muffler bumps.
3. Hold the muffler band clamp in place and tighten the fastener.
4. Check the leading edge of the muffler band clamp to make sure it is positioned on the forward set of muffler bumps.
5. Check the joint on the band clamp to make sure it is centered over the muffler seam. The muffler should be a minimum of (1/16 in) vertically and horizontally when the band clamp is torqued.

NOTE: If a rattle noise is heard at the rear of the vehicle with the engine at idle, the muffler band clamp support bracket locating tab and bolt may be loose. The band clamp support bracket must be torqued.

### VEHICLE ON GROUND, ENGINE OFF - UPPER AND LOWER COOLING MODULE GROMMETS, FOAM STRIP AND WIRING HARNESS (1991 - 1993 VEHICLES)

Refer to the cooling section in the "Engine Mechanical Service Manual" for procedures and replace the lower cooling module grommets with P/N 21030708 (two required). Make sure the new grommets are seated in the pockets of the cradle. If not, relocate the module grommets correctly in the cradle.

NOTE: For 1992 vehicles, built after January 2, 1992, the new lower cooling fan module grommets (P/N 21030708) will be installed during production.

If the vehicle is equipped with A/C, check the upper cooling module foam strip and wiring harness along the forward side of the tie bar for correct positioning, refer to Figure on the next page. If these item are not positioned correctly, refer to the following procedures:

1. Remove the upper cooling module "L" bracket.
2. Position the lamp wiring harness forward of the foam pad.
3. Position the foam pad strip back into the cooling module slots.

NOTE: A new cooling module upper mount "L" bracket assembly with a larger diameter hole (14mm [0.55 in.]) in the grommet is released for all vehicles bilt before VIN MZ123049. The new assembly, P/N 21030616 (two required) can be installed on vehicles equipped with the old type (smaller hole). Refer to "Cooling" section of the "Engine Mechanical Service Manual" for cooling module upper "L" bracket replacement procedures.

4. Check the upper cooling module grommets for binding or misalignmnet and freedom of movement. The cooling module retaining pinsmust be centered in the grommets supported by the "L" bracket(s) and the module should move from left to right, forward and rearward freely a minimum of 3.18mm (1/8 in.). If the grommets are pinched, loosen the "L" bracket(s) and position them. Make sure the locator tang in each "L" bracket is properly positioned in the upper tie bar slot.
5. Tighten the "L" bracket (s) fasteners. Check the cooling module for freedom of movement. It is extremely important that the cooling module is able to move freely, 3.18mm (1/8 in.) minimum.

### DEAREATION HOSE (1991 VEHICLES)

Check the cooling system deareation hose for contact with the front of th dash. If the deareation hose is too long, it can be repositioned in the retaining clamps and/or shortened approximately 1pmm (3/4 in.).

### AIR INLET DUCT, HOOD RELEASE CABLE AND HEADLAMP WIRING HARNESS (1991 - 1994 VEHICLES)

1. Check the SOHC (LKO) engine air inlet duct for correct alignment of arrows (Figure, View A). If arrows are not aligned, position air inlet tube and align indicatore arrows at tube attachment points.
2. Check the SOHC (LKO) engine inlet duct for interference with hood cable and headlamp harness. Adjust if necessary.
3. Check hood release cable and headlamp wiring harness at the inlet end of the air intake snorkel for interfeence (Figure, position "B"). Position cable and/or wiring harness if contacting the air inlet.
4. Make sure foam isolator is properly installed on the upper end of the air inlet snorkel. The small isolator prevents air inlet snorkel contact contact with the vehicles's upper tie bar.

### A/C COMPRESSOR, SUCTION HOSE (1991 -- 1994 VEHICLES)

Check for interference between the A/C suction hose and the corner of the battery tray (Figure, position "C"). It will be necessary to reposition the engine's wiring harness, located on the upper side of the transaxle, to allow download movement of the A/C hose.

It may also be necessary to route the manual transaxle backup switch harness over the A/C hose to allow for downward movement of the wiring harness. The A/C suction hose must not contact the battery tray. Position the hose at the A/C compressor or front of dash as necessary to prevent contact if clearance cannot be obtained by repositioning the engine wiring harness.

### A/C DISCHARGE HOSE (1991 - 1994 VEHICLES)

Check for interference between the A/C discharge hose and transaxle cooler lines (Fiigure, position "D"), and A/C discharge hose and front transaxle mount damper bracket (Figure, position "E" for 1991 vehicles only). The A/C discharge hose must not contact the damper bracket or transaxle cooler lines. Position the line at the condenser or compressor if necessary to prevent contact.

NOTE: If it is necessary to move pipe ends at compressor condenser to obtain clearance, gently flex the pipe only enough to obatain mimimum clearance. Over bending of hose ends will damage them and cause possible refrigerant leaks. Do not try to bend the pipe ends at the thermal expansion valve (TXV).

### ACCESSORY DRIVE BELT AND PULLEYS (1991 VEHICLES)

NOTE: Vehicles built since March 1, 1991, have a new accessory drive belt and will not require inspection or belt replacement. The new accessory drive belts can be identified by a part number on the belt or by measuring the belt thickness.

Accessory Drive Belt Thickness

Old Belt - 4.3 mm + / - 0.3 mm (0.169 in. + / - 0.012 in.)

New Belt - 5.5 mm + / - 0.5 mm (0.217 in. + / - 0.019 in.)

Pulley Inspection

Vehicles built before March 1, 1991, require accessory drive belt and pulley inspection. Inspect the accessory drive pulleys, with engine off, for debris build - up in the pulley grooves. If debris exists, clean the pulley grooves with a cotter key extractor or stiff wire brush. After cleaning pulley grooves, replace the accessory drive belt with a new accessory drive belt.

### VEHICLE ON GROUND, ENGINE OFF

HOOD STOP (S) AND LATCH ASSEMBLY (1991 - 1994 VEHICLES)

Check hood for flutter at idle (in drive "D" for automatic transaxle, or neutral for manual transaxle). Adjust hood stop(s) to fit hood with fenders. If hood still flutters, lower the hood latch assembly as necessary to eliminate condition.

### ENGINE POSITIVE CRANKCASE VENTILATION VALVE (PCV) (1991 VEHICLES)

Check PCV for shuttle/flutter. Listen for noise at the PCV valve with engine at idle and transaxle in neutral. If a noise is suspected, pinch off the hose and listen for a change in sound. Replace the PCV valve if the noise disappears..

### BRAKE POWER BOOSTER CHECK VALVE (1991 VEHICLES)

Caution: THE VEHICLES BRAKING SYSTEM IS IMPARED WHEN THE BRAKE BOOSTER CHECK VALVE HOSE IS PLUGGED. DO NOT OPERATE THE VEHICLE WITH A PLUGGED BRAKE BOOSTER HOSE OR THE CHECK VALVE REMOVED.

Check the power brake booster check valve for high - pitch flutter or rattle noise. Listen at the booster, outside the vehicle, for an audible sound and inside the vehicle near the instrument panel, while having another technician pump the brakes. If a noise is present, remove the hose from the check valve and plug it. Replace the check valve if the noise disappears.

Important: Rattle noises can also occur in the instrument panel and are frequently heard from inside the vehicle. It will be necessary to isolate the noises using the brake booster check valve diagnostic information provided.

### FRONT AND REAR TRANSAXLE MOUNT ASSEMBLY REPLACEMENT (FOR DOHC [LLO]/AUTOMATIC TRANSAXLE) (1991 VEHICLES)

After completing the preceding steps, and if the vibration condition has not been corrected, replace the front and rear transaxle mounts(s) with service replacement parts.

Front Transaxle Mount Replacement (P/N 21011341)

Refer to "Transaxle Front Mount" in the "Powertrain Mounts Service Manual" for removal and installation procedures.

Rear Transaxle Mount Replacement (P/N 21011722)

Refer to "Transaxle Front Mount" in the "Powertrain Mounts Service Manual" for removal and installation procedures.

### DIAGNOSTIC EVALUATION (1191 - 1994 VEHICLES)

NOTE: Minimum Idle Speed (TBI - MFI) adjustments are set at the factory and MUST NOT be tampered with to alter minimum engine idle speed. Improper adjustment of the idle speed screw can cause false PCM codes, idle instability and automatic transaxle shift concers, etc.

After all checks have been completed and a vibration concern is not corrected, test the engine on the service basic analyzer (SEBA or equivalent) diagnostic system. Verify that cylinder power contribution, compression, spark plug wires, fuel quality, DIS module ooperation/grounding, vacuum leaks, PCM coolant sensor, air temperature sensor, MAP, EGR, injector(s), etc. are not causing an intermittent cylinder misfire.

### Parts Requirements:

PARTS REQUIREMENTS | NOTE: The following parts are released to service 1991 and early production 1992 vehicles, except for the lower radiator support grommer P/N lower radiator support grommets were installed in production.
21006620 | SOHC (LKO) - Belt - w/Pump & P/S Pump
21006623 | SOHC (LKO) - Belt - w/Pump & A/C Compr & P/S Pump
21006622 | DOHC (LLO) - Belt - w/Pump & P/S Pump
2100624 | DOHC (LLO) - Belt w/Pump & A/C Compr & P/S Pump
21011341 | Mount Asm - Trans Frt - DOHC (LLO) w/Auto Trans - Service Replacement
21011722 | Mount Asm - Trans Rear - DOHC (LLO) w/Auto Trans - Service Replacement
21011297 | Mount Asm - Eng Motion Restrictor w/MP3 & C41
21011298 | Mount Asm - Eng Motion Restrictor w/MP3 & A/C
21011302 | Isolator - Catalytic Conv Hanger
21011418 | Isolator - Intermediate Exhaust Pipe
21011417 | Bolt - Intermediate Exhaust Pipe Isolator
25097213 | Valve Asm - C/Case Vent Hose (PCV)
21012146 | Valve Asm - Power Brk Booster Vacuum
21030616 | Bracket - Upper Radiator (2 Required) (1991-1993)
21030708 | Grommet - Lower Radiator Support (2 Required)

### Claim Information

To receive credit for this repair, submit a claim through the Saturn Dealer System as follows:

Case Type | Description | Labor Operation Code | Time
--- | --- | --- | ---
VW | Bulletin - Base Time (Includes all inspections and minor adjustments) | T9507 | 0.7 hrs
Add if Required:
A | Replace rear transaxle mount | -- | 0.6 hrs
B | Replace front transaxle mount |  | 1.1 hrs
C | Grease front engine mount restraint cable | -- | 0.2 hrs
D | Replace motion restrictor | -- | 0.8 hrs
E | Replace intermediate exhaust isolator and modify heat shield | -- | 0.3 hrs
F | Replace catalytic converter isolator (one or both) | -- | 0.2 hrs
G | Adjust and/or shim muffler isolator block | -- | 0.4 hrs
H | Reposition upper cooling module foam strip, wiring harness and replace "L" bracket, if necessary | -- | 0.3 hrs
I | Replace lower cooling module grommets (both) | -- | 0.3 hrs
J | Reposition or shorten deareation hose | -- | 0.2 hrs
K | Clean accessory drive belt pulleys and replace drive belt, if necessary | -- | 0.3 hrs
L | Adjust hood stop(s) and latch | -- | 0.2 hrs
M | Replace PCV valve | -- | 0.1 hrs
N | Replace brake booster check valve | -- | 0.1 hrs
O | Complete check on service diagnostic equipment (includes SBEA check) | -- | 0.6 hrs