GM Prizm/Nova 1985-1993 Repair Guide

Spring and Shock Absorbers/MacPherson Strut

Print

TESTING



Shock Absorbers

The purpose of the shock absorber is simply to limit the motion of the spring during compression (bump) and rebound cycles. If the car were not equipped with these motion dampers, the up and down motion of the springs would multiply until the vehicle was alternately trying to leap off the ground and to pound itself into the pavement.

Contrary to popular rumor, the shocks do not affect the ride height of the car nor do they affect the ride quality except for limiting the pitch or bounce of the car. These factors are controlled by other suspension components such as springs and tires. Worn shock absorbers can affect handling; if the front of the car is rising or falling excessively, the footprint of the tires changes on the pavement and steering response is affected. The simplest test of the shock absorbers is simply to push down on one corner of the unladen car and release it.

Observe the motion of the body as it is released. In most cases, it will come up beyond its original rest position, dip back below it and settle quickly to rest. This shows that the damper is slowing and controlling the spring action. Any tendency to excessive pitch (up-and-down) motion or failure to return to rest within 2-3 cycles is a sign of poor function within the shock absorber.

While each shock absorber can be replaced individually, it is recommended that they be changed as a pair (both front or both rear) to maintain equal response on both sides of the car. Chances are quite good that if one has failed, its mate is weak also.

MacPherson Struts

See Figures 1, 2 and 3

The struts are precise parts and retain the springs under tremendous pressure even when removed from the car. For this reason, several special tools and substantial specialized knowledge are required to safely and effectively work on these components. If spring and shock absorber work is required, it may not be a bad idea to remove the strut involved yourself and then consider taking it to a repair facility which is fully equipped and familiar with the car.



Click image to see an enlarged view

Fig. Fig. 1: Front suspension - 1985-88 VIN code 4 engine



Click image to see an enlarged view

Fig. Fig. 2: Front suspension - 1988 VIN code 5 engine



Click image to see an enlarged view

Fig. Fig. 3: Front suspension - Prizm

REMOVAL



See Figures 4, 5 and 6

  1. Under the hood, remove the 3 or 4 small nuts holding the top of the strut to the shock tower. DO NOT loosen the larger center nut.
  2.  



Click image to see an enlarged view

Fig. Fig. 4: Upper strut retaining nuts. Nova with VIN code 5 engine has four, all others have 3 per strut.

  1. Loosen the wheel lug nuts at the appropriate wheel.
  2.  
  3. Raise the vehicle and safely support it. It need not be any higher than the distance necessary to separate the tire from the ground. Do not place the jackstands under the control arms.
  4.  
  5. Remove the wheel. Install a cover over the driveshaft boot to protect it from fluid and impact damage.
  6.  
  7. On Nova vehicles:
    1. Remove the brake flex hose clip at the strut bracket.
    2.  
    3. Disconnect the brake flex hose from the brake pipe at the strut. Remove the brake hose clips. Use a small pan to catch any leakage.
    4.  
    5. Pull the brake hose back through the opening in the strut bracket. Plug the lines to prevent any dirt form entering.
    6.  
    7. Remove the 2 brake caliper mounting bolts and remove the caliper. Hang it out of the way with a piece of wire. Do not allow it to hang by the flex hose and do not disconnect the hose from the caliper.
    8.  
    9. Mark the position of the adjusting cam for reassembly.
    10.  

  8.  



Click image to see an enlarged view

Fig. Fig. 5: Use care in disconnecting the brake lines. Nova above, Prizm below



Click image to see an enlarged view

Fig. Fig. 6: Marking the Nova camber shim before removal

  1. On Prizm vehicles:
    1. Disconnect the brake hose from the brake caliper and drain the fluid into a small pan.
    2.  
    3. Remove the clip from the brake hose and remove the hose from the bracket.
    4.  
    5. Disconnect the ABS sensor wire from the shock absorber if so equipped.
    6.  
    7. Use a sharp instrument or scribing tool to make matchmarks in all three dimensions on the steering knuckle. The strut must be reinstalled in its exact previous position.
    8.  

  2.  
  3. Remove the 2 bolts which attach the shock absorber to the steering knuckle. The steering knuckle bolt holes have collars that extend about 5mm. Be careful to clear them when separating the steering knuckle from the strut assembly.
  4.  

Press down on the lower suspension arm in order to remove the strut assembly. This must be done to clear the collars on the steering knuckle bolt holes when removing the strut assembly.

  1. Remove the strut assembly. Remember that the spring is still under tension. It will stay in place as long as the top nut on the shock piston shaft is not loosened. Handle the strut carefully and do not allow the coating on the spring to become damaged.
  2.  

DISASSEMBLY



See Figures 7 and 8


CAUTION
This procedure requires the use of a spring compressor; it cannot be performed without one. If you do not have access to this special tool, do not attempt to disassemble the strut. The coil springs are retained under considerable pressure. They can exert enough force to cause serious injury. Exercise extreme caution when disassembling the strut.



Click image to see an enlarged view

Fig. Fig. 7: Marking the Prizm steering knuckle before disassembly



Click image to see an enlarged view

Fig. Fig. 8: GM tools for compressing the spring and disassembling the strut. Equivalent tools may be rented from a reputable supply house.

  1. Place the strut assembly in a pipe vise or strut vise.
  2.  


WARNING
Do not attempt to clamp the strut assembly in a flat jaw vise as this will result in damage to the strut tube.

  1. Attach a spring compressor and compress the spring until the upper spring retainer is free of any spring tension. Do not over-compress the spring.
  2.  
  3. Use a spring seat holder to hold the upper support and then remove the nut on the end of the shock piston rod.
  4.  
  5. Remove the bearing plate, the support and the upper spring retainer. Slowly and cautiously unscrew the spring compressor until all spring tension is relieved. Remove the spring and the dust cover.
  6.  

Do not allow the piston rod to retract into the shock absorber. If it falls, screw a nut onto the rod and pull the rod out by the nut. Do not use pliers to grip the rod as they will damage its surface, resulting in leaks, uneven operation or seal damage. Be extremely careful not to stress or hit the rod.

INSPECTION



Check the shock absorber by moving the piston shaft through its full range of travel. It should move smoothly and evenly throughout its entire travel without any trace of binding or notching. Use a small straightedge to check the piston shaft for any bending or deformation. If a Prizm shock absorber is replaced, the old one should be drilled at the bottom to vent the internal gas. Wear safety goggles and drill a small hole (2-3mm) into the base of the shock absorber. The gas within the strut is colorless, odorless and non-toxic, but should be vented to make the unit safe for disposal.

Inspect the spring for any sign of deterioration or cracking. The waterproof coating on the coils should be intact to prevent rusting. A quick check for a cracked spring is to hit the spring sharply with a small metal mallet or wrench handle. An intact spring will resonate, similar to a distant gong; a cracked spring will have much less resonance and a distinctly different sound.

Check the upper strut mount assembly for any abnormal noise, binding or restricted motion. Lubricate the upper bearing with multi-purpose grease before reinstallation.

ASSEMBLY AND INSTALLATION



See Figures 9 and 10


WARNING
Never reuse a self-locking nut. Always replace self-locking nuts with new hardware.

  1. Loosely assemble all components onto the strut assembly. Make sure the mark on the upper spring seat is facing the outside of the vehicle.
  2.  



Click image to see an enlarged view

Fig. Fig. 9: Make sure the upper strut seat marks face to the outside during reassembly.

  1. Compress the spring, carefully aligning the shaft guide rod with the hole in the upper mount. Align the lower spring seat. Do not over-compress the spring; compress it just enough to allow installation of the shaft nut.
  2.  
  3. Install the shaft nut and tighten it until the strut shaft begins to rotate.
  4.  
  5. Double check that the spring is correctly seated in the upper and lower mounts and reposition it as needed. Slowly release the tension on the spring compressor and remove it from the strut assembly.
  6.  
  7. Tighten the shaft nut to 34 ft. lbs.
  8.  
  9. On Nova vehicles, install the camber adjusting cam into the knuckle, observing the matchmarks made during disassembly.
  10.  



Click image to see an enlarged view

Fig. Fig. 10: The strut to knuckle bolts must be set to the correct tightness.

  1. Place the strut assembly in position and install the strut to knuckle attaching bolts. Tighten the bolts to the correct torque:

    Nova with VIN code 4 engine: 105 ft. lbs.
     
    Nova with VIN code 5 engine: 166 ft. lbs.
     
    All Prisms: 194 ft. lbs.
     

  2.  

  1. Using a floor jack and a piece of wood, gently elevate the control arm to the point that the upper mount can be aligned with the holes in the shock tower. Insert the bolts into the upper holes and install the nuts. Tighten the nuts to 23 ft. lbs. (Nova with VIN Code 4 engine) or 29 ft. lbs. (Nova with VIN code 5 engine and all Prizms).
  2.  
  3. Pack the shaft nut area with grease and install the dust cover.
  4.  
  5. On Nova vehicles, install the brake caliper and tighten the bolts to 65 ft. lbs. Pull the brake hose through the strut bracket opening and connect the fitting. Tighten the fitting to 11 ft. lbs. Install the flex hose clip at the strut bracket.
  6.  
  7. On Prizm vehicles, install the brake hose in the bracket and install the clip. Connect the hose to the caliper and tighten the fitting to 22 ft. lbs. Connect the ABS sensor wire to the shock absorber, if so equipped.
  8.  
  9. Install the wheel and install the lug nuts snugly.
  10.  
  11. Lower the vehicle to the ground. Tighten the wheel lug nuts to 76 ft. lbs.
  12.  
  13. Bleed the brake system and top up the brake fluid level. Please refer to Brakes for complete directions.
  14.  

 
label.common.footer.alt.autozoneLogo