My MacBook Pro makes 3 successive tones, a 5 second pause (repeating) My MacBook Pro makes 3 successive tones, a 5 second pause (repeating).

According to Apple, this indicates RAM does not pass a data integrity check.

So how can I fix it?
Three beeps on startup is typically a memory self-test error symptom.

This article is providing some tools to test your RAM :

http://www.cnet.com/news/troubleshooting-tools-memtest-and-rember/