Already did it, (mem test, hdd test, processor test) I suppose, the crash is so suddenly, than the logs can't be written. the only thing I can see, is the report engine failing over mysql, then squid crash, then server crash...

If there is nothing in the logs, it is going to be difficult. Can you monitor "top" and see if something is hogging resources? Can you check your hard disk (smartmontools can be installed with yum)/ If you pull the system down can you do a memory test?

thank you nick, I am running squid in cacheless mode. disk space is more than ok.

There is a sandboxed version of MariaDB installed (system-mariadb). How is your disk space "df -h"? Once you've done that, can you clear your proxy cache?