I was reading surge brake info on another site ( I have my own problems) and found this I hope it helps reminded me of your problem.
Brake Coupler Trailer Parking Warning !!
When parking a trailer EQUIPPED with HYDRAULIC SURGE BRAKES it is important to be sure that the BRAKE COUPLER is pulled back forward to the fully telescoped [ TOWING ] position prior to final disconnecting of the trailer from the tow vehicle.
[ 1 ] Any HYDRAULIC BRAKE COUPLER that has a cast iron master cylinder, and is left with the brake coupler partially, or fully compressed [ as it would be when backing up ], will have part of the interior of the cast iron master cylinder wall exposed to the atmosphere.
Many times this will result in corrosion of the exposed cast iron cylinder wall, and will result in the fact that the piston in the master cylinder will not extend back to it's normal towing position the next time the trailer is towed.
This will result in hydraulic pressure being maintained on the trailer brakes, while towing, and will probably result in damage to the trailer braking system. This could result in a catastrophic accident !!
This phenomenon does not normally occur in brake couplers with COMPOSITE or ALUMINUM master cylinders, however it is a good policy to be sure that the brake coupler is fully extended to the towing position prior to disconnecting the trailer from the tow vehicle.
[ 2 ] A second reason to be sure that the brake coupler is fully extended to the towing position is that if hydraulic pressure is left on the trailer brakes while parked, the brakes shoes of a drum brake system, or the brake pads of a disc brake system will be maintained in FULL contact with the brake drum, or rotor. Many times this will result in the bonding [ sticking ] of the shoes or pads to the co-ordinate braking surface.
This will often result in a trailer that has the brakes locked up when the tow vehicle is attached. Sometimes jerking the trailer forwards, and backwards is enough to break the corrosion bond that has developed however sometimes the brakes must be disassembled to relieve the problem.
[ 3 ] SAFETY FIRST --- BE SURE THE BRAKE COUPLER IS FULLY EXTENDED BEFORE DISCONNECTING FROM THE TOW VEHICLE.
THIS MESSAGE IS BROUGHT TO YOU BY CHAMPION TRAILERS
AT CHAMPION TRAILERS WE ARE CONCERNED ABOUT YOUR TRAILERING SAFETY
©2002 CHAMPION TRAILERS