Our Maytag dishwasher model MDB4000 leaks from the door, but not every use. The leak started just on the left corner, but now sometimes leaks from the middle. The diswasher is 12 years old.

Try replacing the door gaskets. It should fix the problem..
This maybe what is causing the leak

http://www.appliancepartspros.com/whirlpool-dishwasher-door-gasket-902894-ap4111635.html

I have the same problem with my dishwasher. I have replaced the door seal and it still leaks. It seems like the channel where the seal fits is just a little too deep for the seal. As a temporary fix, I pull the door seal out of the channel about 3/8 inch on the side that leaks before closing the door to run the dishwasher. When the door closes, it pushes against the seal and that seems to work for me. A more permanent solution would to be to add about a 1/8 inch filler gasket into the channel then put the door seal back. That way the seal will press on the the gasket instead of bottoming out into the channel. Hope this helps you.

Hi,

Here is a tip that I wrote about dishwashers and them leaking.

Leaking Dishwasher

heatman101

Hi,

Here is a tip that I wrote about dishwashers and them leaking.

Leaking Dishwasher

heatman101

dfg

Check the door gasket for proper seating. Try a new gasket.

Hi,
Here is a tip that I wrote about dishwashers and them leaking.

Leaking Dishwasher

heatman101
sthyushg

Have the same dishwasher and happens sometimes to mine when the door doesn't close properly because it is hitting the cabinet front. Try pulling up and forward from the bottom of the door when it is closed. if the bottom comes forward this could make the difference and stop the leak.

Hi,

Here is a tip that I wrote about dishwashers and them leaking.

Leaking Dishwasher

heatman101

f

Try to touch the lower door seal, it sometimes jumps out of its place when you open the dishwasher door. You may consider replacing the seal with a new one, I have to push the seal on my dishwasher to its proper place before every cycle. It is quite annoying, but free :-)

On this model the vent is open and shut by a wax motor. The vent should be closed tight during the entire wash cycle and the first 6 minutes of the drying cycle. Check the operation, make sure there is not a bunch of gunk restricting it. If you are handy with a meter check the resistance of the motor. It should read approx. 2100ohms. Another reason for leaking at the base is oversudzing. Also check the upper spray arm for cracks or splits shooting water into the vent area. Catriver...post back.