[394220]

Guessing the age as it was in the house when we bought three years ago.
I have purchased new racks as the ones in the machine have badly rusted. The bottom one was easy to replace. I don't know how to remove the plastic stoppers at the end of the top runners in order to replace the top rack (model number # 99001454). Very grateful for any advice. I don't want to break it, after making the fairly expensive decision to replace the racks rather than the machine.

[PS Staff - Sheila]

On the rack stops at the end of the rails you will see arrows.

Pull the stop in the direction of the arrows and it will release the locking tab.

Then pull the stop out.

Here is a link to your dishwasher model MDB4040AWA.

Here is the stop in the open position.