My outdoor a/c unit is making a large grinding noise for a few seconds when it starts up, but only when it is extremely hot or humid outside. I also see some water near the compressor and under the brass pipes.

Video: https://photos.app.goo.gl/12is41kTSxVyK3Sg9

Can somebody tell me what I should do?

 

It sounds like your Carrier 38TDB unit is near the end of its life.

I never liked that Bristol compressor. The Scroll compressor with an unloader is a much better product.

I wonder if stage 2 is dropping out?
I would get the amperage of the yellow wire to the compressor in both stages of cooling.
Yellow is common with that model for some strange reason.

If stage two of the compressor drops out I would expect the delta tee across the indoor coil to be 11 degrees instead of 18 to 20.

I cover the bottom opening that displays the compressor with the control box panel and the lay the larger panel horizontally to cover the rest of that area when testing.
You will trip out the high pressure switch tying to test it totally uncovered.


.