My 96 Mercury Grand Marquis is making a water rushing noise just behind the dashboard on the passenger side. I was told it could mean that the Heater box drain is plugged but I cannot find a drain. Can anyone advise?

Asked by Nov 10, 2013 at 03:05 PM about the 1996 Mercury Grand Marquis 4 Dr GS Sedan

Question type: Maintenance & Repair

Loud water rushing sound behind the passenger side dashboard when accelerating.  Not sure what is causing it but I do not have water in the vehichle.  I Was told it may be a clogged Heater box drain but cannot find the drain to clean out.

3 Answers


Passenger side, down low on the firewall, should be about 1 to 2 inches long, it could be painted so have a good light source when looking, sometimes getting under the vehicle makes it a little easier to find.

2 of 2 people found this helpful.

Thank you I believe I found it but I can't get to it without taking things apart so I will bring to mechanic. Thank you very much for your time and expertise.


Before taking to a mechanic, check the drain holes on the bottom of the inside of the passenger door. That door doesn't normally get used as much as the driver door and can get clogged with leaves,dirt, etc. They can get plugged up and the door will actually fill up with water and slosh around when accelerating. There should be 2 oblong holes on the bottom of the door. Open the door and look right where the weatherstripping runs along the bottom of the door. You should see the drain holes. Stick a flat tip slotted screwdriver up thru those two holes and see if a gush of water comes flowing out. That happen on my '91 Crown Vic last fall. I must have had 2 gallons of rainwater in my pasenger door. You'de be surprised how much water a door can hold if those drainholes are plugged up. Good luck, Kenny/MrBlueOval

3 of 3 people found this helpful.

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