I also did a Google search on 2005-2009 Mustangs with rain leakage problems. Here are a few different things I found:
- Remove passenger tire and check seal between inner fender and chassis. Seal could even be missing.
- Take off the plastic cowl as if you were going to change the cabin filter, look inside for the rubber grommets in the firewall. Missing or defective.
- Foam seal between the hard black plastic weather strip retainer and the a-pillar.
- Here's a Ford TSB. Unfortunately the pictures aren't around anymore:
WATER LEAK - FRONT FLOOR AREA
Publication Date: December 15, 2008
This article supersedes TSB 07-14-6 to update the model years, part list and service procedure.
Some 2005-2009 Mustang vehicles may exhibit a difficult to diagnose water leak in the front floor area. This may be caused by loose grommets and/or sealer skips around the cowl area, loose A-pillar window weatherstrip retainer, misaligned body harness grommet through the firewall, misaligned body harness grommet from the passenger door.
Follow the Service Procedure steps to correct the condition.
O NOT REMOVE THE DASH OR THE DASH INSULATOR AT ANY TIME DURING THIS PROCEDURE.
Water Leak Testing Procedure
To pressurize the cabin open trunk and remove the floor carpet. Remove the plastic tail panel cover. Remove side carpet push pins and move the carpet aside. Locate the body vents in the lower rear corners of the trunk (rear of wheel wells) and tape them off. Close the trunk. Place the blower motor on high. Turn air recirculation to off mode. Close windows and doors. Open the hood and spray soapy water along body seams / grommets, particularly around the A-pillar / fender and hood hinge area, and check for bubbles.
O NOT REMOVE COWL GROMMETS DURING WATER TESTING. (FIGURE 7 AT END OF ARTICLE)
Using a garden hose equipped with a shower head attachment, or similar device, run water onto the vehicle being sure to direct water over the roof ditch moldings, side window weather strips, and windshield / cowl panel area. While water is being applied to the vehicle, have an assistant inside the vehicle verifying the location of the water intrusion.
Water Leak Inspection / Repair Procedure
Inspect the following areas for visible signs of leaks and follow the appropriate repair steps.
Verify that the plastic cowl panel grill is evenly seated against the windshield and not warped. If warped, replace with current service stock.
Remove the cowl panel grill. Refer to Workshop Manual (WSM), Section 501-02, and inspect for proper cowl panel mount grommet installation and pinch weld sealing. Water may enter the cowl channel, through the cowl panel grommets / seals or forward pinch weld, potentially causing a sloshing sound and/or water leaking down the dash kick panel area. If there is standing water in the cowl channel, remove by siphoning through a cowl panel mount grommet hole. (Figures 7-8 - end of article)
Verify that the ten (10) cowl panel mount grommets and seals are installed and sealing tightly to the vehicle. If any are missing, or the seals are damaged, replace as necessary. (Figure 1)
Figure 1 - Article 08-26-7
Remove old cowl grommets and clean entire cowl surface with a suitable wax and grease remover. If silicone and/or seam sealer was used to seal grommets, ensure all sealer is removed before installing new grommets.
With surface clean and prepped, snap the hot melt cowl grommet into cowl panel.
Using a suitable heat gun, heat the hot melt cowl grommet until the hot melt material begins to squeeze out from under the plastic grommet. Do not over heat the grommet because deformation of the plastic grommet may occur.
After heating the grommets, a light amount of pressure may be applied to the outer perimeter of the grommet to help sealing.
Do not over heat around windshield or fender edges or damage may result.
NOTE:HEAT SEALED GROMMETS WERE USED IN PRODUCTION STARTING WITH VEHICLES BUILT ON 9/4/2008.
Inspect the cowl panel to bulk head pinch weld and A-Post to cowl joint for any skips in seam sealer or excessive gaps between panels.
To ensure a water tight seal, apply a small amount of Motorcraft Seam Sealer to the pinch weld and work into seam with fingertip, leaving a small amount on the edge, especially near the windshield center bracket area. (Figure 2)
Figure 2 - Article 08-26-7
O NOT USE SILICONE.
Check the main body wiring harness grommet for proper seating into the bulkhead on the driver / passenger side.
Position the grommet into the bulkhead making sure the grommet is fully seated and sealed. If there is any aftermarket wiring installed through the grommet, reroute and seal as necessary. To ensure proper sealing around the wiring harness grommet, apply a small amount of Motorcraft Seam Sealer and install the grommet. (Figure 3)
Figure 3 - Article 08-26-7
Verify that the door to the A-pillar wiring harness grommet is fully seated into the A-pillar.
To ensure proper sealing around the wiring harness grommet, apply a small amount of Motorcraft Seam Sealer and install the grommet into the A-pillar. (Figure 4)
Figure 4 - Article 08-26-7
Remove and inspect the foam seal of window weatherstrip retainer at the A-pillar. Tears in the foam seal may allow water to enter the vehicle, between window weatherstrip retainer and the A-Pillar, and travel inside the interior A-Pillar trim molding into the dash kick panel area. (Figure 5)
Figure 5 - Article 08-26-7
Replace window weatherstrip retainer, if foam seal is damaged. (Figure 6)
Figure 6 - Article 08-26-7
Assemble other trim as required.
If no leaks are found in these areas, refer to WSM, Section 501-00 for water leak diagnostics.
PART NUMBERPART NAME
9R3Z-6351238-ARetainer-Weather Right Side
9R3Z-6351239-ARetainer-weather Left Side
TA-2Motorcraft Seam Seal
Eligible Under Provisions Of New Vehicle Limited Warranty Coverage
IMPORTANT: Warranty coverage limits/policies are not altered by a TSB. Warranty coverage limits are determined by the identified causal part.
MT082607Use SLTS Operations If Available; Claim Additional Diagnosis Or Labor Performed As Actual TimeActual Time
BASIC PART NO.CONDITION CODE
Figure 7 - Article 08-26-7
Figure 8 - Article 08-26-7
NOTE: The information in Technical Service Bulletins is intended for use by trained, professional technicians with the knowledge, tools, and equipment to do the job properly and safely. It informs these technicians of conditions that may occur on some vehicles, or provides information that could assist in proper vehicle service. The procedures should not be performed by "do-it-yourselfers". Do not assume that a condition described affects your car or truck. Contact a Ford, Lincoln, or Mercury dealership to determine whether the Bulletin applies to your vehicle. Warranty Policy and Extended Service Plan documentation determine Warranty and/or Extended Service Plan coverage unless stated otherwise in the TSB article. The information in this Technical Service Bulletin (TSB) was current at the time of printing. Ford Motor Company reserves the right to supercede this information with updates. The most recent information is available through Ford Motor Company's on-line technical resources.
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