Cowl seal leaking is a problem that plagues both the e36 and e46 model cars. You will first notice either a damp mildew smell inside the vehicle after it has been closed up for a while and there may also be constant moisture inside the passenger compartment. At some point you will notice that the passenger carpet or floor mat is wet!

What has happened is there is a leak at the lower windshield plastic cowl that is allowing water to fill the cavity under the cover; this in turn will spill over into the passenger compartment. This may occur each time it rains or when you have your vehicle washed. If you suspect this is your situation here is what you do.

With the hood closed inspect the area where the windshield and the plastic hood cowl meet. This is the space where the wiper blades hide when they are not in operation. This area of the plastic hood cowl has a flexible rubber seal that fits snuggly to the windshield, which diverts the water to the drain rails at the hood. This is near where the fenders and windshield meet. What occurs is that over a period of time the rubber seal deteriorates, gets brittle, and cracks away. This leaves a gap of approx. 1/4 inch, allowing water to enter the space behind the cowl and into the passenger compartment. Due to the slapping direction of the wipers the wiper blades essentially push the water into this cavity. The water also enters the DME compartment.

The solution is to replace the entire plastic cowl. Before you start, the project will require some basic hand tools, some mechanical skills, and patience. Total project time is approx. 30 minutes. The only danger is, don't drop the spring loaded wiper arms onto the surface of the windshield (it will break!), and you must reinstall the wiper arms in the precise location to avoid the blade going the wrong direction and possibly damaging the paint.

First: With the wiper switch in the off position, the wipers should be in the rest position at the base of the windshield. Using some whiteout, mark the exact wiper blade location. Raise the hood, and locate the base of the wiper arms and pry away the protective cap covering the locating nut. Using a 13mm socket or wrench remove the nut. Hold the arm to keep it from trying to rotate with the nut. Once the nut is removed the arm should release. Be careful to not scratch the windshield.

Second: Unscrew the 6 plastic locating screws that secure the cowl. There is three located on each side.

Third: Remove the rear hood seal that clips over both the metal firewall and plastic cowl cover. You may now remove the cowl. Clean out the area, and clean the lower windshield, but make sure to leave the whiteout marks for the wiper blades. Remove any leaves, pine needles, and other debris that has collected under the left and right corners of this area. A shop vacuum works very well.

Fourth: Install the new cowl cover using the new plastic screws. Do not over tighten; doing so will curl the seal up creating a gap. If there are any slight gaps, use a thin bead of silicone glue under the seal and use blue masking tape to hold it until it cures.

Now the water will properly channel to the edges for drainage.