Hatchback Lid - Service Kit to Reduce Helicopter Noise
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FILE IN S.I. Man VOL. I
SEC. 8 PG. 86
Service Information
SUBJECT: SERVICE KIT TO REDUCE THE OCCURENCE OF ISSUE: 02/85-743 "HELICOPTER NOISE" 1979-, 900 W/HATCHBACK
During 1984 production and beginning with VIN Serial Nos. (approx.) E1027914 and E2013262, a bracket was attached to each side of the rear lid of hatchback models to reduce the chance of "helicopter noise". This noise can be described as a pulsating pressure or a low-frequency sound due to oscillation of the rear lid, generated by movement in the suspension.
A kit is now available for earlier (up to mid-M84) cars with complaints of this problem. The following diagnosing procedure may be followed to determine what repairs are necessary.
NOTE: The service kit will not eliminate possible air buffeting caused by certain combinations of sunroof opening and air speed over the car.
Parts Involved:
Quantity
69-16-050 Support Kit 1 per car
92-92-756 Hatch Support Wedges 2 per car (optional)
Diagnostic Procedure
Listen closely to the customers' comments and then test drive* the car with the customer. Unnecessary repairs may be avoided if the complaint is not affected by the following diagnostic procedure.
- The sound is most likely to occur at road speeds of approximately 40-46 mph and again at considerably higher speeds.
- The sound is dependent on the balance and trueness of the wheels and of the nature of the road surface.
- The sound is not affected by engine speed, gas pedal position or engine braking.
- The sound level is noticeably reduced if tire pressure in the rear tires is reduced to 15 psi (approx. 1 bar). This indicates that a tire problem is contributing to the helicopter noise problem. Note this measure is only for test drive procedures. Only drive for short distances and refill the tires afterwards.
Repair Details (must be followed in numerical order to eliminate unnecessary repairs) Perform each check in the order that they appear here. It may not be necessary to complete all repair details. Stop when the problem is solved.
1. Check and, if necessary, adjust the contact between the hatch door and the support wedges and the position of the hatch latch if the door is difficult to close or open.
(Time allowance for the above is Oper. #83222, 0.2 hour.)
Test drive* the car and check for noise.
2. If good contact pressure cannot be achieved on both sides of the hatch and the car is before VIN Serial No. D1035054 and D2013174 replace the support wedges with later type (P/N 92-92-756).
(Time allowance for the above is 0.2 hour.)
Test drive* the car and assess the results. If not satisfactory proceed with step 3.
3. Dynamically balance all 4 wheels and visually inspect them for lateral and radial run out. If a wheel is suspect, it is advisable to road test* the car with a known good wheel. If this achieves good results closely examine the bad wheel.
(Time allowance for the above is Oper. #77113, 0.2 hour, per wheel. Problems with wheel balance are not warranty.)
4. Check the shock absorber bushings and replace damaged or worn bushings.
(Time allowance for the above is Oper. #76132, 0.4 hour, per shock absorber.)
Test drive* the car and assess the results. If not satisfactory, continue with step 5.
5. Position the support holder from kit (P/N 69-16-050) and mark the position on the rear hatch, 220 mm from the center of the pivot for the gas-assisted shock absorber.
Drill two 1/8" (3.2 mm) holes and mount the holder together with the zinc washers and sheet metal screws supplied.
Fit the rubber bumper and adjust the height.
Fit the protective tape into the bottom of the gutter.
(Time allowance for the above is 0.5 hour.)
*Time allowance for each road test is 0.2 hour straight time.
Warranty Information: Use the time allowance noted above. For Failure Code, use 83221-05-0-01-05 for problems occurring in "Repair Details" 1, 2, and 5. Use Failure Code 76132-08-3/4/5-01-01 for no. 4.