GM Bonneville/Eighty Eight/LeSabre 1986-1999

Belts

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INSPECTION



See Figures 1 through 6

Once a year or at 12,000 mile intervals, the tension and condition of the drive belts should be checked, and, if necessary, adjusted. Inspect the belts for signs of glazing or cracking. A glazed belt will be perfectly smooth from slippage, while a good belt will have a slight texture of fabric visible. Cracks will usually start at the inner edge of the belt and run outward. All worn or damaged drive belts should be replaced immediately. It is best to replace all drive belts at one time, as a preventive maintenance measure, during this service operation. Loose accessory drive belts can lead to poor engine cooling and diminish alternator, power steering pump, air conditioning compressor or Thermactor air pump output. A belt that is too tight places a severe strain on the water pump, alternator, power steering pump, compressor or air pump bearings. Inspection of the belt may reveal cracks in the belt ribs. The cracks will not impair belt performance and should not considered a problem requiring belt replacement. Belts should be replaced if sections of the belt ribs are missing or if the belt is outside the tensioner's operating range. The material used in late-model drive belts is such that the belts do not show wear. Replace belts at least every three years.

On all vehicles, except those equipped with supercharged engines, a single serpentine belt is used to drive all accessories formerly driven by multiple drive belts. Supercharged engines use two accessory drive belts. The outer belt drives the supercharger, while the inner belt drives the alternator, power steering pump, water pump and A/C compressor. The accessories are rigidly mounted with the belt tension maintained automatically by a spring loaded tensioner.



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Fig. Fig. 1: There are typically 3 types of accessory drive belts found on vehicles today



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Fig. Fig. 2: An example of a healthy drive belt



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Fig. Fig. 3: Deep cracks in this belt will cause flex, building up heat that will eventually lead to belt failure



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Fig. Fig. 4: The cover of this belt is worn, exposing the critical reinforcing cords to excessive wear



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Fig. Fig. 5: Installing too wide a belt can result in serious belt wear and/or breakage



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Fig. Fig. 6: The supercharged engines use 2 accessory drive belts

TENSION MEASUREMENT



1987-92 Vehicles
  1. Inspect the tensioner markings to see if the belt is within operating lengths. Replace the belt if it is excessively worn or is outside of the tensioner's operating range.
  2.  
  3. Run the engine with all of the accessories off for until the engine is warmed up. Shut the engine OFF . Using a belt tension gauge No. J 23600-B or equivalent, placed halfway between the alternator and A/C compressor (if equipped), or between the power steering pump and the crankshaft pulley (if not equipped with A/C), measure the belt tension. Note the reading.
  4.  
  5. With the accessories off, start the engine and allow to stabilize for 15 seconds. Turn the engine OFF . Using a 18mm box end wrench, apply clockwise force to the tensioner pulley bolt. Release the force and record the tension immediately, without disturbing the belt tensioner position.
  6.  
  7. Using the 18mm wrench, apply counterclockwise force to the tensioner pulley bolt and fully raise the pulley to eliminate all tension. Slowly lower the pulley to the belt and take a tension reading without disturbing the belt tensioner position.
  8.  
  9. Average the three readings. If the average of the three readings is lower than 67 lbs. (298 N), and the belt is within the tensioner's operating range, replace the belt tensioner.
  10.  

1993-99 Vehicles
  1. Run the engine, with no accessories on, until it is warmed up or for about 10 minutes.
  2.  
  3. Shut the engine OFF , then check the belt tension using J 23600-B or equivalent belt tension gauge. Place the belt tension gauge as follows:
    1. Except supercharged engines: Place the gauge halfway between the alternator and the power steering pump.
    2.  
    3. Supercharged engines: Place the gauge halfway between the supercharger and the idler pulley.
    4.  

  4.  
  5. Note the reading, then remove the gauge.
  6.  
  7. Start the engine, with the accessories off, and allow the system to stabilizer for 15 seconds, then shut the engine OFF . Using a 15mm or 18mm socket, as applicable, apply clockwise force (tighten) to the tensioner pulley bolt. Release the force, then immediately record the tension reading without disturbing the belt tensioner position.
  8.  
  9. Using the 15mm or 18mm socket, as applicable, apply counterclockwise force to the tensioner pulley bolt and raise the pulley to eliminate all tension. Slowly lower the pulley to the belt and take a tension reading without disturbing the belt tensioner position.
  10.  
  11. Average the three readings. If the average is not between 50-70 lbs. (125-315 N) and the belt is within the tensioner's operating range, replace the tensioner.
  12.  

BELT ADJUSTMENT



Belt tension is maintained by the automatic tensioner and is NOT adjustable. If the belt slips or is out of minimum tension range, you need a new belt.

REMOVAL & INSTALLATION



See Figures 7 through 13

  1. Disconnect the negative battery cable.
  2.  



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Fig. Fig. 7: Many vehicles have an accessory drive belt routing label affixed to the radiator shroud

  1. Remove the belt guard or coolant recovery reservoir as required.
  2.  
  3. For 1996-99 supercharged engines, perform the following:
    1. Raise and safely support the vehicle.
    2.  
    3. Remove the right-hand splash shield.
    4.  
    5. Remove the connector from the crank sensor.
    6.  

  4.  
  5. For 1996-99 vehicles, remove the engine mounting bracket lower nut, stud and spacer. Carefully lower the vehicle.
  6.  


CAUTION
To avoid personal injury when rotating the serpentine belt tensioner, use a tight fitting wrench that is at least 24 in. (61cm) long.

  1. Take note of the belt's routing. Lift or rotate the tensioner using a suitable sized breaker bar in the square opening or box end wrench on the pulley nut. Remove the belt from the pulleys.
  2.  



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Fig. Fig. 8: You can use a box-end wrench on the pulley nut to rotate the tensioner ...



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Fig. Fig. 9: ... then remove the belt from the pulleys



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Fig. Fig. 10: Serpentine drive belt routing and removal - 3.8L (VIN L) engine shown, VIN C similar



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Fig. Fig. 11: Make sure to note the drive belt routing prior to removing it - 3.8L (VIN K) engine shown



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Fig. Fig. 12: Drive belt removal on a 1992-95 supercharged engine

To install:

Be sure the belt is aligned into the proper grooves of the accessory drive pulleys.

  1. Lift the tensioner, and install the belt onto pulleys. Make sure the belt is routed properly.
  2.  



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Fig. Fig. 13: Many vehicles have a label you can check to be sure the belt is installed and routed correctly

  1. For 1996-99 vehicles, raise and safely support the vehicle. Install the engine mounting bracket lower spacer, stud and nut.
  2.  
  3. For 1996-99 supercharged engines, perform the following:
    1. Attach the connector to the crank sensor.
    2.  
    3. Install the right-hand splash shield, then carefully lower the vehicle.
    4.  

  4.  
  5. Install the belt guard or reservoir.
  6.  
  7. Connect the negative battery cable.
  8.  

 
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