Do 502 errors have any impact on website rankings?

502 = bad开发者_StackOverflow gateway (php-fpm problems, etc.)

Does googlebot consider them 503? (503 = server overloaded & try again later)

google supports HTTP 502

http://www.google.com/support/webmasters/bin/answer.py?answer=40132

and treats them as

502 (Bad gateway)

The server was acting as a gateway or proxy and received an invalid 
response from the upstream server.

in my experience google treats 502 as downtime and stops hammering your server for some (short) time.