can I Re- encryp my wallet with a wallet.dat file from before encryption My computer crashed and I lost access to my bitcoin wallet.. before that happened I knew I had lost my passphrase so when trying to recover my wallet with my wallet.dat I looked for a very early dated wallet.dat and loaded that, when it came up it was not encrypted so I encrypted it.

and made a new passphrase should that bring my wallet back with all the coins with the new encryption
No, it will not bring back any of your coins. The encryption process regenerates all of the private keys in your wallet. Furthermore, the private keys generated are not based on your password in anyway; they are random. So re-encrypting an unencrypted backup will not let you get access to your lost Bitcoin.