Trailer Brake Bleed

I had to replace a brake line on my trailer over the weekend. I was pretty sure I got all the air out of the lines by manually bleeding the system. I basically had someone at the bleeder screw on the caliper opening and closing as I used a screw driver to work the actuator pin. I took it down the highway and the brakes seemed to be working well. I stopped to check the temp of the hubs at the on / off ramps and they were always within 5 degrees of each other. However the road to my house is a little curvy and I am sure the brakes were actuating off and on. When I got home I noted the temps in the picture. The last caliper in the brake line (furthest away from the actuator) had a really low temp. Also note that the temps start with the hottest to coolest going away from the actuator. Do you think I still have some air in the lines that the last caliper isn’t grabbing tight? Or another issue going on? I am going to pull the calipers and clean and grease them as well.

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I would suggest using a power bleeder just to be sure. Cheap insurance vs toasting an axle seal and available to borrow/rent from some auto parts stores. The manual method with the screwdriver is kind of a pain, and mostly works, speaking from experience...

Sorry I can't compare as I only have brakes on my front axle.

Yeah, I am thinking about buying one of those vacuum bleeders for $30 on Amazon.


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If you have an oil extractor for your boat already just it.

You can have someone putting fluid in as you pump the extractor.

Next time anyone needs to do this. Before breaking the line loose, use a clamp to push the actuator and tighten to hold down. It acts like a straw and the liquid won't move. Replace the line, caliper, etc. the release the actuator. You will only have air in the piece you removed. If this is a caliper your bleeding takes 3 pumps not a power bleeder.

Great tip. And yes, I have an oil extractor. Didn’t even think about it.


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I would also make sure the temperature difference is not due to any low grease in the wheel bearing hubs. Unless they are sealed?

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Hubs are good. Truth be told, I actually pulled all 4 to clean out and replace all the old hybrid grease and check bearings. That is how I broke the brake line. [emoji849]


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