My whirlpool dishwasher model # WDT780SAEM1 makes a loud popping noise when I open and shut the door. What is causing it and how do I fix it?

The loud popping noise that you're hearing when you open and shut the door of your Whirlpool dishwasher (model # WDT780SAEM1) is most likely caused by the door gasket. The door gasket is the rubber seal that runs around the door, creating a tight seal when the door is closed.
Here are a few things you can try to fix the issue:

1. Check the gasket for damage: Inspect the door gasket for any tears, cracks, or other damage. If you find any damage, you will need to replace the gasket.
2. Clean the gasket: Over time, debris and food particles can accumulate on the gasket, causing it to become stiff and not seal properly. Clean the gasket with a mild detergent and warm water, and then dry it thoroughly.
3. Check the door alignment: Make sure that the door is properly aligned and not hitting the gasket when you open and shut it. If the door is not aligned properly, you will need to adjust it.
4. Lubricate the hinge: If the door gasket is in good condition and properly aligned, the problem may be with the hinge. Try lubricating the hinge with a silicone-based lubricant, as this can help to reduce friction and noise.
5. Contact Whirlpool: If you have tried all of the above steps and are still unable to fix the issue, contact Whirlpool customer service for further assistance. They will be able to provide you with additional troubleshooting steps or advice, or they may need to send a technician to repair or replace the dishwasher.