Is this a sign of just being a grumpy old dog?

Definitely try the vet first! A similar situation happened to me once, my normally very sweet dog snapped at me. Turns out he was sick (an overgrowth of bacteria in his tummy) and just wasn't feeling good and didn't want to be touched. Once he was better it never happened again!

Your dog needs to be checked by your vet, a change in behavior like that usually indicates a physical problem, he may well be in pain and needs vetting, dogs try not to show pain, it's a survival tactic, doesn't mean he isn't hurting from something, could be arthritis at his age.

As several people have accurately pointed out, Milan's tactics are cruel and useless, his t.v. shows are heavily edited to show results. Use his outdated, demented tactics and you likely will get bitten.

He's an actor, not an animal behaviorist and got his loopy theories by watching roving gangs of street dogs in his native Mexico to which he adds psycho babble to convince ignorant dog owners that he's onto something.

Ceasar Milan is a jerk and an animal abuser and I would NEVER use his tricks on my dog. If you mention his name to real pet rescue folks you'll get an earful!

Changes in behavior at this age can often mean there is a change in health - often totally fixable. Years ago my bosses dog was doing something similar and it turned out she had a totally rotten tooth that was causing her great pain.

It sounds to me like you are a conscious and loving pet owner who is truly concerned about your dog. I suggest a vet checkup, less than $50 for peach of mind and don't pay any more attention to Ceasar Milan and his misguided antics.

Instead of using that actor, Milan's, tactics on your senior dog, have you ever thought about getting him to the vet for a geriatric health check? Sounds like a dog in pain!!

wow! that is very weird... did he act like this before??? if not id be worried.