How to Change the Brake Fluid in Trailer Brakes

If you've never changed the brake fluid in your trailer, consider this: Over time, brake systems absorb moisture, causing vapor pockets to form when the brake fluid heats up. Because vapor pockets interrupt the steady flow of brake fluid, the result could be disastrous---you could find yourself pushing the brake pedal to the floor and finding it to have no effect on the forward motion of your trailer. Fortunately, replacing the old brake fluid in your trailer is relatively inexpensive if you do the work yourself.

Instructions

1

Park your trailer on a paved, level surface.

2




Loosen the wheel's lug nuts before lifting the trailer with a floor jack.

Turn each wheel's lug nuts with a tire iron or lug nut wrench just enough to loosen them.

3

Raise one side of the trailer with a floor jack and lower it onto a jack stand. Do the same on the opposite side.

4

Finish removing the lug nuts on each wheel with a tire iron or lug nut wrench. Remove the wheels. Behind each wheel you'll find a caliper, which sits atop the rotor.

5

Locate the bleed valve on one of the calipers. A bleed valve is a small nozzle on the left or right side of a caliper. Slip one end of a bleed hose over the bleed valve.

6

Pour brake fluid into a disposable container until it's about one-third of the way full. Hang the other end of the bleed hose into the container, making sure the tip is submerged in the brake fluid. This helps prevent air from backing up into the brake line.

7

Locate the master cylinder, which can be found near the coupler at the front end of the trailer. Remove the lid.

8




Use a turkey baster to remove old brake fluid from the master cylinder reservoir.

Insert the tip of a turkey baster into the reservoir and siphon out as much brake fluid as possible, putting the old brake fluid in a separate disposable container.

9

Refill the reservoir with new brake fluid.

10

Locate the bleed screw, found next to the caliper's bleed valve, and turn it with a locking wrench. This will open the bleed valve to allow the old brake fluid to be released.

11




A flat head screwdriver is required to release the old brake fluid from the line.

Insert a flat head screwdriver into the hole on top of the coupler housing and push down until it's wedged under the pushrod nut. You'll know you're in the right spot when turning the screwdriver releases brake fluid through the bleed hose.

12

Apply pressure to the pushrod to flush the brake fluid from the line. When the fluid in the master cylinder reservoir gets low, refill it; allowing it to completely drain will result in air getting into the brake line. Also keep an eye on the disposable container to make sure it doesn't overflow.

13

When the brake fluid running through the bleed hose appears to be clean, release the pressure on the pushrod and tighten the bleed screw with a locking wrench.

14

Refill the reservoir and repeat the process on the other caliper.

15

Put the wheels back on the trailer and tighten the lug nuts with a tire iron or lug nut wrench.

16

Lift the trailer with a floor jack, remove the jack stands and lower the trailer to the ground.