COWL AREA WATER LEAK DIAGNOSIS AND REPAIR

Model and Year 1976-84 CHEVETTES

This bulletin covers the possible causes of front end water leaks on past and present model Chevettes along with the diagnosis and repair procedure necessary to correct them.

SYMPTOMS

Front end water leaks may be indicated by:

- water on top or under the front carpet. - water in the glove box. - water in the rear floor area. - a musty odor in the vehicle.

CAUSE

Front end water leaks may be caused by various items. Figure 1 illustrates the locations of the following areas:

1. Sealer skip at the inner fender to cowl seam.

2. Poor sealer adhesion at the windshield pillar to cowl joint flange.

3. Cracked sealer at the coach joint.

4. A bridge in the MIG weld at the windshield opening lower corner.

5. Sealer skip under the windshield reveal moldings.

DIAGNOSIS

More than one (1) leak may be present on a vehicle in any or all of the areas detailed in Figure 1. In order to ensure that a satisfactory repair is performed the first time, the following procedure is recommended:

1. Loosen the sill plate, remove the kickpad and fold back the carpet on the affected side of the vehicle. Inspect for signs of leaking.

2. Seal off the coach joint and lower windshield by placing a piece of tape over the coach joint and windshield reveal moulding on the affected side (see Figure 2).

3. Use an unrestricted water flow directed into the gap between the fender and the hood. This will duplicate driving in a heavy rain (see Figure 3).

If no water enters the vehicle, the inner fender to cowl seam and the windshield pillar to cowl joint flange are OK, proceed to Step 5.

OR

If water enters the vehicle, it is probably due to poor sealer adhesion at the windshield pillar to cowl seam (see Figure 1). In order to isolate the exact cause of the leaks, proceed as follows:

4. Seal the die relief hole (Figure 4) with a piece of strip caulk.

Retest for leaks as shown in Figure 3.

If the leak now stops, it is probably due to a sealer skip at the inner fender to cowl seam. Follow repair procedure 'A' as described below.

- Retest for water leaks as shown in Figure 3, then proceed to Step 5.

OR

If water still enters the vehicle, the leak is probably due to poor seal adhesion at the windshield pillar to cowl joint flange.

Follow repair procedure 'B' as described below:

- Retest for water leaks as shown in Figure 5, then proceed to Step 5.

5. Remove the tape from coach joint and retest for leaks with an unrestricted water flow as shown in Figure 6.

If not water enters the vehicle, the coach joint and lower windshield opening MIG weld are OK, proceed to Step 8 and water test the windshield for leaks.

OR

If water is now entering the vehicle, it may be due to a poor seal at the coach joint, or a gap in the MIG weld at the windshield lower corner. Proceed as follows to locate the problem.

6. Insert an air nozzle into one of the upper access holes behind the kick pad and apply low pressure air (less than 205 KPA/30 PSI) (see Figure 7).

It may be helpful to attach a length of copper tubing to the air gun.

7. Place a bubble solution or glass cleaner (GM P/N 992727 or equivalent) over the coach joint and lower corner of the windshield (see Figure 8) and bubble test the area.

- Repair the coach joint or weld leaks as described below in Part 'C' and 'D' of the repair procedure as required.

- Retest with water only and proceed to Step 8. (Air pressure at this stage might damage the repair.)

8. Use an unrestricted waterflow to leak test the windshield sealant (see Figure 9). Start at the base of the test area and work upwards.

If leaks are detected at this point, refer to Section II of the Fisher Bcdy Service Manual.

REPAIR PROCEDURE (see Table 1 for materials list)

A. Inner Fender to Cowl Seam

- Seal the inner fender to cowl seam (Figure 10) with a brushable seam sealer or an aerosol rubberized undercoating.

- Seal seam as far up on cowl as possible.

NOTICE: When using a brushable sealer, it may be necessary to use a brush with an extended handle in order to reach hidden areas.

- Fill in the die relief hole with a thumb grade sealer (see Figure 4).

- Re-water test.

- Continue diagnosis at Step 5 above.

B. Windshield Pillar to Cowl Joint Flange

- Loosen the fender by removing the top five (5) and two (2) rear screws.

- Pull back the fender to expose the windshield pillar to cowl joint.

- Bubble test the flange area as per Steps 6-7 of the diagnosis (see Figure 6, 7, and 11).

- Remove existing sealer using a suitable tool.

- Repair area by applying a brushable medium body sealer.

- Re-water test.

- Reinstall fender and continue diagnosis at Step 5.

C. Coach Joint Leak

- Dig out and remove as much of the existing sealer as possible using a suitable tool.

NOTICE: Loosening of the fender may be required as per windshield pillar to cowl joint flange repair procedure (B).

- Apply a flow grade paintable sealer to the joint and force the sealer into the gap.

- Refinish area as required after testing is complete.

- Retest with water only and continue diagnosis at Step 8.

D. Mig Weld Windshield Opening Lower Corner

- Slide the escutcheon located at the lower centerline of the vinyl reveal moulding to one side.

- Pry one (1) edge of the moulding out of the urethane.

- When the moulding is removed about 75mm (3 inches), grasp the moulding by hand and slowly pull away from the body.

- DO NOT remove the entire moulding but stop about 75mm (3 inches) up from the bottom of the windshield opening.

- Cut away any loose urethane that is exposed in the MIG weld area.

- At this point, inspect for any corrosion or damaged metal around the MIG weld area and repair as necessary using established procedures.

- Clean and reprime exposed areas with the primer supplied in the windshield repair kit (GM P/N 9636067 or equivalent).

- Trim the lower barb off the reveal moulding using a sharp knife (see Figure 13).

- Apply enough urethane in exposed areas to fill gap and to retain the reveal moulding.

- Force the moulding back into place.

NOTICE: Tape may be required to hold the moulding in place until the urethane cures.

- Flood the area with lukewarm water in order to cure the urethane.

- Slide the escutcheon back into place.

E. Windshield Water Leak

- Repair windshield leaks as descibed in Fisher Body Service Manual under Section 11 Stationary Glass - water leak correction.

MATERIALS

Location Description 3M Kent Dominion Sure Seal -------- ----------- -- ---- ------------------ Inner Fender to Paintable Joint & Seam Quick Leak Seam & Joint Cowl Seam Wind- Medium Body Sealer (Black) Check SEALER Cartridge shield Pillar Sealer 08648 Wet/Dry (Black) CSB to Cowl Joint 10510 Flange Rubberized Undercoating Aerosol 08883

Coach Joint Paintable Drip Check Black Sure Mastic Flo Grade Sealer Mastic PBM/PWM Body Sealer 08521 SM-1 104300

Windshield Urethane Windo-Weld Wet/Dry Resealant + GM P/N Resealant Resealant (Pump Grade) Windshield 9636067 08633 Pump Grade PRS opening (RWD) MIG Weld 10590

Die Relief Hole Thumb Grade Strip Caulk Seal "N" Strip Caulk Sealer (Black) Caulk (Strips) Black 08578 Black (SP-1) BSC1 10310

Diagnosis GM Glass or Soap Cleaner Solution P/N 992727

TABLE I

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.