Descargar grub2: ftp://ftp.gnu.org/gnu/grub/

yum install bison gcc flex make 
 
tar -zxvf grub-2.00.tar.gz 
cd grub-2.00
./configure
make
make install

/usr/local/sbin/grub-mkconfig -o /boot/grub/grub.cfg
/usr/local/sbin/grub-install /dev/sda
 
yum remove grub
 
reboot