What Might Cause Surge Trailer Brakes to Apply When Driving

Updated 02/11/2025 | Published 12/03/2024

Question:

I have a 2006 Rangertrail. Replaced a leaking, outdated system. The original part numbers were replaced with the current identical parts. The actuator is LP 70, caliphers are 46304. New slider pins. Bled the system, no air after being bled. Replaced the solinoid when I replaced the other parts. The brakes are very hot when towing. Can only touch for a moment. Hubs are hotter still. The RPMs are high on my truck, plus 500, and I lose 4mpg towing. Placing a lockout pin on the coupler resolves both of these issues.Brakes, wheel cool to touch, RPM lower and 4mpg plus towing. The brakes are locked out, and I can feel the difference stopping. My question, what do I change or adjust to keep the brakes from dragging ? Huge difference in tempture, towing w/o being locked out. My prior Rangetrail, with the same systen had zero issues. Is there an adjustment on the threaded rod ? Where else do I look ? Thank you in advance. Dean

asked by: Dean L

Expert Reply:

Hey Dean, that is a really odd problem to have when towing forward. It sounds like somehow your brake system is getting pressurized which is causing them to at least partially apply the trailer brakes. When towing forward I can't really determine what might cause this but maybe on a long shot is the trailer really nose down and it's pushing the actuator forward and applying the brakes slightly?

You should be able to see the inner member of the actuator slide in as you lower it onto the ball mount if so.

Is there possibly a breakaway lever pulled on the actuator?

expert reply by: Jameson C

Dean L.

2/11/2025

Thanks for the reply. Disassembled the actuator and brake cylinder today. What is the correct location of the set bolt and locking bolt on the threaded rod. Distance ? Moved the set bolt to the end of the threaded shaft, and tightened the lock bolt. This looks like pulling forward on the coupler would pull the brake cylinder forward. The old replaced unit had the two bolts about 1" from the bottom of the threaded shaft. Could this placement apply some preasure to the brake cylinder causing my hot brake issue ? Going to bleed the system when the rain stops, and do a short road test. Any other thoughts ? Thanks. Dean

Jameson C.

2/11/2025

@DeanL I don't have a way to know for sure since that's an older actuator but I would go with the setting that you pulled out and found as that would most likely be accurate. That setting should not be able to put pressure on the master cylinder to create braking pressure. Are the brake assemblies manual adjust? Could they have been adjusted too tight?