Sizzling Sound When Replacing Battery?

You obviously have some shorted components. If you examine the logic board around the area you described with a magnifying glass, you should be able to see where the damage is.

To tackle liquid damage, you must be prepared for a long and tedious process.

First, you need to displace the water completely by removing the logic board using this guide, soak it in 90%+ isopropyl alcohol, then clean it with a soft brush.

It would be even better if you could remove the shields, but that requires soldering tools and an experienced tech.

While the board is soaking, you have to clean and dry the lightning connector assembly.

You also must look at all the connectors that connector to the board, such as the tip of the screen assembly cables, the battery cable, the lightning cable, the volume and power control cable, and if they have black marks, clean them as well. Don't let alcohol touch the screen as it will ruin it.

Pay special attention to the home button and home button cable. If you ruin it or it is ruined by the water, you may end up with a brick.

Also make sure you are very gentle. Some components are made of "glass" and are easy to chip, whereas is chipped, will render your phone useless.

FINAL NOTE: if you see lots of damaged areas (corrosion, burnt components, breakage, etc.), I recommend putting everything back in place and paying for a replacement from Apple.