Bleeding trailer surge brake fluid - single handed

Drcoffee

Petty Officer 1st Class
Joined
Aug 26, 2021
Messages
220
The brake system is pretty basic on a trailer. I just bought this boat last August and I thought it might be a good time to flush the brake fluid, and it needed it. Who knows the last time it was done.

I started by sucking most of the old fluid out of the resevior, then refilling with fresh fluid. Installed the ball hitch in the receiver (not attached to vehicle) in order to activate the brake master cyl. Starting on the furthest bleeder screw (drivers side), I cracked the 3/8” bleed screw loose and attached the catch cup hose. The trick is to raise the cup above the bleeder screw. Once the fluid leaves the wheel cyl, any air in the line will continue to float up and away from the bleed screw. Any back flow will be pure fluid. Once the cup was in place, I used the attached hitch as a lever to pump the brakes. pushing slowly down and slowly raising the hitch, about 1/3 of the fluid gets purged. Refill the res each time. I cycled the brakes 5 times and checked to make sure the fluid leaving the bleeder looked new. Once the old fluid was removed, I locked down the bleeder, removed the hose and wiled it clean. Give the bleeder a final tightening and replace the rubber cap. Then move to the other side. Repeat

you do not need a pressure bleeder or a partner to pump the brakes like you do in a car. Just dont let the master run dry. I also use this method on my cars and it works great. Here are some pictures from the job. Note where the cup is and how the hose is routed.
 

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Last edited:

mike_i

Master Chief Petty Officer
Joined
Jun 28, 2017
Messages
879
I basically do the same but I start with the passenger side rear first.
 

jhande

Chief Petty Officer
Joined
Jun 26, 2010
Messages
442
Always start with the wheel cylinder farthest from the master cylinder.

A bit tricky on some cars with an ABS module. But yes an old trick for mechanics to bleed brakes by themselves.
 

Drcoffee

Petty Officer 1st Class
Joined
Aug 26, 2021
Messages
220
What came out was like maple syrup. Dark and thick. Never seen fluid that bad before. For many people, the trailer is an after thought. Just run it until it breaks. Honestly, it took 20 minutes to do it. on a 1-4 wrench scale, its a 2 wrench
 

Lou C

Supreme Mariner
Joined
Nov 10, 2002
Messages
11,802
I just did mine today. Used the same one man bleeder kit (Lisle), works well, my brake fluid came out looking just like what went in. The last time I changed the backing plates was about 6 years ago so I got pretty good life from them. Installed a 6,000 lb axle & 12" drum brakes to replace the 3500 and 10" drum brakes.
 
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