clunking in surge brakes

Good Morning ! Hoping for a little insight. I have a 2005 trailer that has the hydraulic surge brakes on it and I am going to be replacing the front acuator, spring and the back up coil as one complete unit. My question is currently, when I stop at a stop sign and then proceed forward, there is a clunking sound and it jerks on the truck plenty aggressive. Is this normal?? Or will this clear itself up after I replace that complete asm? Just hoping to be able to know what I should expect after the job is done. Any replies are greatly appreciated. thanks.

Shouldn’t clunk once replaced.

Your master cyl is not building pressure. As a result the plunger collapses in farther than normal when you stop. Then when you take off the free play is taken up and causes the clunk. It will disappear with the new system provided the brakes are properly bled. Back bleeding with a pressurized bleeder is the best way and far easier. Good Luck

My last 2 boat trailers with surge brakes have clunked since the day they were new. Tried bleeding them and no change. I just live with it.

There is a rubber stop in the hitch to alleviate this problem yours is probably worn out or gone. My Shorelander trailer was doing the same thing rubber bumper was totally gone. If it is still there and you have drum brakes the pads need adjusting. There should be very little play between brakes off and brakes on for surge breaks.

Is the clunk from the brakes or a loose hitch? If your trailer has a swing tongue, this can be very dangerous. Check both the pin and the pivot bolt. As for a loose hitch, there is a bracket that stops the slop in the hitch to stinger. Costs under $20 on Amazon.

Have you checked the brake fluid level in the reservoir on the actuator? I’ve had the same problem a few times and it seems like if I add some brake fluid and then stick a big flat bladed screw driver in the hole in the top of the actuator and manually pump the actuator several times, the problem goes away. It appears that I must have a very slow leak somewhere that’s causing my brake fluid level to drop over time.

I have a Tie Down system on my trailer. Good luck.

thank you for all the relplies… new actuator is on its way… will report after it gets installed