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Ford Mustang V6 2005-2014: Why is My Car Leaking Inside?

If water gets inside your Mustang, it can lead to all sorts of problems. This article will show you how to figure out the cause of the leaking and put an end to it.

By Jared Hammond - October 15, 2015

This article applies to the Ford Mustang V6 (2005-2014).

You get into your Mustang to drive to work and you notice some sloshing in the passenger's side foot well. For some unfortunate owners, this is all too common after a heavy rain. For certain '05 to '08 models, multiple issues can cause flooding in the passenger foot well. To find the leak, you can spray water on the car with a hose and have someone sit inside watching for the leak. Keep reading and work your way through the problem to eventually find the source of the leak.

Materials Needed

  • New seals (optional)
  • Ratchet and socket set

Step 1 – Check the cowl drain

The drain could be clogged, forcing water into the cabin. To clean it, position the windshield wipers straight up and unscrew the passenger side of the cowl panel. Pull back the cowl panel and remove the passenger cabin air filter. At the bottom of the well, you should see the small rubber drain. You can just pull the drain out from underneath, clean it, then put it back in. Don't forget to clean out any debris still trapped in the well and replace the cabin air filter when you're finished.

Figure 1. Cowl drain.

Step 2 – Replace the cowl panel grommets

The seals around the grommets may have deteriorated to the point where they now leak. Ford determined this to be one of the main causes of the recurring leak problem, so for later models they changed to a heat-sealed grommet that wouldn't leak. To get the new heat-sealed grommets, order part# 9R3Z-63517C58-A. You'll need a total of ten of these grommets.

Installation is simple. Pry off the old grommets and insert the new grommet into the cowl panel. Use a heat gun to warm the grommet until the seal contracts. Push in the grommet to seat it to the cowl panel. Then repeat for the other nine grommets.

Figure 2. Cowl panel grommet.

Featured Video: Ford Mustang Grommet Water Leak Fix

Pro Tip

Make sure you cover up the windshield with a hot pad, so you don't accidentally heat up the seal on the windshield.

Step 3 – Check the main body wiring harness grommet

Sometimes, when doing wiring work, the grommet will be unseated and allow water in. It's located behind the passenger's side kick panel. First check the grommet to ensure that it's properly seated. If it is seated but water is still getting in, you can apply addition sealant around the grommet.

Figure 3. Wiring harness grommet in passenger foot well.

Step 4 – Check the seam and seals

A bad seam or seal will allow water in. Places to check are the seam between the A-pillar and cowl panel, as well as the seals around the windows and windshield. Also, check the seals along the bottom of the doors. Then finally check underneath the car and look for any vulnerable points. Be aware that there are already drainage holes specifically for letting water out of the car. What you need to be on the look out for are small gaps and cracks where things should be flush. If you do find a gap, adding more sealant should be able to fix it.

Figure 4. Check the window seals.

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