Knocking noise under hood

2010 HYUNDAI ELANTRA
151,032 MILES • 4 CYL • 2WD • AUTOMATIC
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TIFFNICOLE
  • MEMBER
  • 1 POST
Recently I accidentally left my gas tank open in the rain for about twenty minutes. I am not sure if water got in it or not but ever since then my car has been making a loud knocking noise when turned on. What could this be?
Sep 28, 2018 at 8:20 AM
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DANNY L
  • ✓ASE Certified Mechanic
  • 5,648 POSTS
  • ASE Certified Mechanic
Hello, I am Danny.

That is possible that water did get into the tank. Water is not combustible so that could explain the "knocking" sound under the hood. I would suggest having the fuel system flushed and put in fresh gas. There is an additive call"Seafoam" that might help in the meantime but definitely you need to get the contaminated gas out. I have attached a picture of what the can looks like. Hope this helps and thanks for using 2CarPros.
Danny-
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Sep 28, 2018 at 2:15 PM
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