Heat up the bolt for 5" mins then give it another try. The extension snapped off,the head still stuck in the 19mm socket, lucky i bought it from craftsman brand, i'll head to sears to get the replacement.
Here is the pic.

 

Suggest also heating and trying your air impact again. The 300 ft-lb rating may not get it done even w/ heating but worth a try.

good luck

 

I don't like those store bought crank pulley hold downs my friend bought one on line and he called me over to help hold it in place while he broke the nut free . I made one like that before they where selling them, when all that was available was the ones from honda. anyway mine is a tight fit and I have a 1/2 inch bolt sticking out where you have your breaker bar. I turn the engine till the bolt hits and stops on the frame. then I put a 3/4 19mm impact socket and a 3/4 breaker bar . no extensions. on the six cyl. I put it on heavy duty jack stands and I put back up props in case it falls of the stands. then I get under the car with my two hands I grab hold of some thing under the car and kick the 3/4 breaker bar . usually one tick will do it . you would be amazed how much stronger your legs are . on the 4 cyl you grab the bumper and kick. Ive probably done 20 to 30 accords like this and it works every time . kind of scarey being under the car and kicking with all your might. I dont advise anyone to use this method.
I have a lot of heavy duty equipment to be safe. I was a bus mech. for 30 years. so I have a lot of big tools

 

you may try taking it to a mechanic and telling him your problem, he will probably have better air tools and can loosen it and re-tighten it to spec for $20 or $30. The bolt is very tight but the problem is breaking the weld that develops with time. I did a lot of rocking on the bolt before it finally snapped free. I just didnt apply full force which may have been what snapped the extension.

 

I've heat it up for 10 mins and used the impact gun but it still wouldn't move...

 

Thanks for the advice, i'll head back to sears to get the 3/4 breaker bar and 3/4 19mm socket. So we don't need extension for that??

 

The car isn't drivable at the moment and I've removed the alternator, and power steering pump. I just dont want to put everything back together. This is frustrating.

 

I tried this and found the 3/4" drive x 19mm socket would not fit through the restraint tool (socket OD > tool ID). I tried 1/2" x19mm socket w/ 3/4x1/2 reducer to 3/4 breaker bar. The reducer sheared (two of them from sears).

Your best option may be a more powerful air impact. This may cost less than paying someone to break the bolt for you, and you'll have the air impact for the future. I believe my Ingersol Rand cost about $125 several years ago. It is rated for over 500 ft-lbs impact torque. W/ heat this has worked for me on a very tight Acura MDX crankshaft bolt.

good luck

 

you're right, i just tried it again today and it sheared of. I'm thinking about the more powerful impact gun, i'll do more research online to find a bigger one.

 

Harbor Freight has a 3/4" drive air impact that may be an option. I have no idea about quality, but it's not something you'll use everyday. A big air impact requires good air flow; larger reservoir and 1/2" bore air hose to get the power to the tool.

My IR works good w/ 3/8" air hose (short at about 15 ft). Air hose couplings also provide restriction.

good luck