Re: surge brake coupler clunk question....
Who is the manufacturer of the actuator? Often they will have a website with instructions on how to bleed the brakes. The basic procedure is to get a one man brake bleeder kit (Lisle makes one you can buy in auto parts stores) and start with filling the master cylinder with fluid. Follow the instructions that come with the bleeder kit. You fill the little container with brake fluid, and put the rubber connector on the bleeder valve on the caliper. Open the bleeder valve, and then pump the actuator (there may be a slot in the cover of the actuator,that you can put a screwdriver in to pump it, or if not use the drawbar and the ball from your trailer to pump it). Look to see if there are air bubbles in the line from the bleeder valve to the container. Keep checking the master cylinder to make sure it is still full. Repeat with the other caliper, until there are no bubbles. Close the bleeder valve before removing the line to the container to keep out air. I did mine this summer in about 10 min (drum brakes). With discs, the only things that can cause that are air in the system, or maybe a problem with the actuator or the mounting of the calipers. I don't think that much clunking is normal, with my Tie Down model 66 there is really no clunk to speak of.
