BMW Coupes and Sedans 1970-1988 Repair Guide

Strut Inserts

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TESTING



The basic test for strut insert performance is the vehicle"s behavior on the road. Strut insert have the job of eliminating spring bounce shortly after the car hits a bump. If the car tends to lose control over washboard surfaces or if there is any sign of fluid leakage, strut insert work is required.

If you're uncertain about strut insert performance, you can jounce test the car. To do this, rest your weight on the front bumper and bounce it repeatedly, in sympathy with the natural rhythm of the springs until the car is bouncing up and down as fast as you can make it. Then release it, and carefully observe its behavior. The car should move upward, then return to its normal riding height and virtually stop. Several bounces after release indicates worn strut inserts.

REMOVAL & INSTALLATION



With the MacPherson strut type front suspension used on BMWs, the strut inserts are an integral part of the strut. Since the strut and associated parts are a very expensive assembly, the strut inserts in front are replaceable. This is an extremely difficult job requiring a good deal of specialized mechanical skill and a number of special tools.

All Models

See Figures 1, 2 and 3


CAUTION
This procedure calls for the spring to be compressed. A compressed spring has high potential energy and if released suddenly can cause severe damage and personal injury. If not comfortable with dealing with a compressed spring, have a professional technician remove the spring from the strut for you.

  1. Remove the strut from the vehicle and mount in a vise using a strut holder. This will prevent damage to the strut tube.
  2.  
  3. Using a proper spring compressor, compress the spring and lock into place. Use all the safety hooks provided and never point the compressed spring at a person.
  4.  
  5. Remove the top nut of the strut mount. Counterhold the strut rod during removal.
  6.  
  7. Pull the strut mount off the strut rod. Note the positioning of the spacers and washer for replacement.
  8.  
  9. Pull the spring off the strut and place somewhere safe. Do not release the compression of the spring.
  10.  



Click image to see an enlarged view

Fig. Fig. 1: With the spring and rubber bump stop removed, loosen and remove the strut insert gland nut



Click image to see an enlarged view

Fig. Fig. 2: Slide the strut insert out of the housing. Some inserts will come out in pieces



Click image to see an enlarged view

Fig. Fig. 3: Before installing the new insert, pour oil or full strength engine coolant into the strut housing

  1. Remove the rubber bump stop, and replace if worn.
  2.  
  3. Remove the gland nut at the top of the strut housing. Turn the nut and allow the pressure to bleed off. A special tool is sometimes needed to remove the nut. Some aftermarket strut manufacturers provide a tool with the replacement cartridges.
  4.  
  5. Pull the old cartridge out of the strut and pour out the oil or fluid in the strut housing.
  6.  

To install:
  1. Fill the strut tube with enough engine oil or full strength anti-freeze so when the new cartridge is installed, oil fills the tube but doesn't overflow. If the strut rod diameter is greater than 1.3 inches (33mm) do not use oil.
  2.  
  3. Install the new cartridge and any spacers that where provided by the strut insert manufacturer. Install the gland nut and tighten to 94 ft. lbs. (130 Nm).
  4.  
  5. Install the spring and strut mount with all the spacers and washers in their original positions. Tighten the new strut rod nut to 47 ft. lbs. (65 Nm).
  6.  
  7. Release the spring slowly and check that it seats in the spring holders. Install the strut in the vehicle.
  8.  

 
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