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When the line broke off the brake actuator did it not lock up the front tire?

If you lost the line it would not affect anything until you apply the brakes, the brake chamber needs air to actuate the brakes. Once you apply the brakes you will get a big air leak. I have heard people just capping off one line in a pinch just to be able to move the coach. I would not recommend this unless it was an emergency. 

If you lose air to the parking brake chambers on the drive axle then the brakes will apply. The parking brake is held open by air pressure, if you lose that air pressure then the spring brake applies the parking brake automatically. This is the difference between service brakes and parking brakes. The parking brake uses air to release the brake, the service brakes need air to apply the brakes. This is why air system maintenance is so important.