Cowl - Snapping or Popping Noise
86chevy15NUMBER: 86-B-53
GROUP: 2B-Light Duty Cab
DATE: March, 1986
SUBJECT: COWL POPPING NOISE
MODELS: 1983-86 S/T JIMMYS
On some 1983-86 S/T Jimmys operating in low ambient temperatures, a condition may exist where a snapping or "popping" noise is heard coming from the cowl. This noise is caused by an "oil can" effect between the windshield frame and the door frame. The service procedure for eliminating the noise is as follows:
1. Remove the windshield wipers and radio antenna.
COWL VENT ASSEMBLY:
2. Remove the cowl vent panel fasteners (Figure No. 1).
Figure No. 2:
3. Place tape on the fender edge and cowl panel edge to prevent paint damage (Figure No. 2).
4. Disconnect the windshield washer hose from the nozzle.
5. Remove the cowl panel, being careful not to scrape the cowl panel on the inner hood edge or fender.
6. Pull back the hood hinge seal to expose the windshield frame and close the hood.
COWL VENT ASSEMBLY:
7. Measure 1-1/4" down from the bottom of the windshield and make a horizontal mark on the windshield frame inboard of the cowl screen lock tab (Figure No. 1).
8. Measure 7/8" inboard from the cowl screen lock tab and make a vertical mark through the line made in the previous step.
9. Center punch the windshield frame at the point the lines intersect. Use a one inch hole saw to cut a hole in the windshield frame (cut through only the first layer of sheet metal) and remove the circular piece of metal that remains from cutting the hole. DO NOT CUT THE SECOND LAYER PANEL.
10. Drive the door frame (the second layer of sheet metal) down with a punch approximately 1/4" all the way around the hole.
11. Paint the bare metal edges left from cutting the hole with a zinc rich primer.
12. Completely fill the hole with black RTV, GM P/N 1052917, or equivalent and level for good adhesion and appearance.
13. Follow Steps 6-12 on each side of the vehicle.
14. Reinstall the hood hinge seals in their original position to prevent water leakage into the cowl. If it is necessary, additional adhesive (3M weather strip adhesive P/N 08001 or equivalent) should be used to secure the hood hinge seal.
15. Reinstall the windshield washer hose, cowl vent panel, radio antenna, and windshield wipers, and remove the protective tape from the fender and cowl vent panel.
Time to perform this modification is 0.6 hrs. Use Labor Operation T 7230.