bleed brakes?

[bec484]

does anyone know how to bleed the brakes on a boat trailer?

 

[Topol_86]

Re: bleed brakes?

If it's the type that activates from the weight of the trailer pushing forward against the tow vehicle, I believe the process is similar to bleeding brakes on a car, only instead of pumping the brakes, you block the tires of the trailer and reverse against it to actuate the brakes. An assistant is needed for this task. If anyone has any easier solutions, by all means share. This is the process we used for my boss' trailer brakes. (My trailers are small and don't have brakes)

 

[Bob's Garage]

Re: bleed brakes?

After much trial and error this is what I ended up doing, by myself. I have a tandem axle trailer with disc brakes. Feel free to adapt to your circumstance.

I attached a tube to the bleed screw at the last caliper in the brake line. This tube was attached to a bottle and submerged in a small quantity of brake fluid.
Do not "crack" the bleeder, yet.

Next I coupled the tow vehicle to the trailer, attached the wiring. Opened the cap on the master cylinder of the trailer, topped off the fluid. Block the wheels to keep the trailer from backing up.

I then gently reversed the tow vehicle to compress the surge actuator, put the transmission in park, applied the park brake. This maintained pressure on the trailer's master cylinder.

I then went to the bleeder with the tube attached and "cracked" it open, allowing the fluid and bubbles to flow until no bubbles present. Closed the bleeder.

Went back and topped off the fluid in the master cylinder, and repeated the process until no more bubbles were present. Just because I am anal, after repeating the process on each of the other calipers, I did it all again..

The brakes work great now.

A couple points of interest:

If you have disc brakes you must make sure the trailer wire is attached to the tow vehicle to make sure you bleed the solenoid during this process.

I made a "pressure bleeder" so as to be sure I had a continuous flow of fluid to the master cylinder. This enabled me to actually drop the trailer tongue to the ground allowing me to use gravity to raise the bubbles in the line to the rear.

Hope this helps. There will be others with easier methods I am sure.

Bob

 

[oldjeep]

Re: bleed brakes?

I made a "pressure bleeder" so as to be sure I had a continuous flow of fluid to the master cylinder. This enabled me to actually drop the trailer tongue to the ground allowing me to use gravity to raise the bubbles in the line to the rear.

Hope this helps. There will be others with easier methods I am sure.

Bob

Do you have a picture of the master cylinder hookup for your pressure bleeder? I've got a motive products pressure bleeder that I use on my jeep and hotrods but have never figured out a good way to make an attachment that will seal on my trailer MC.

 

[marcortez]

Re: bleed brakes?

Read but never attempted......was to actuate the "breakaway" lever a few times.
This forces fluid down the lines (bleeder valve open) and bleeds the air and fluid out.
Or so the story goes ..

 

[This_lil_fishy]

Re: bleed brakes?

There has got to be a better way, this seems potentially dangerous to me. I need to do the same thing, but am looking at maybe taking the coupler apart to see if it can be compressed with a clamp or something.

Ian

 

[dockwrecker]

Re: bleed brakes?

My pressure bleeder looks like this one minus the gauge (don't need it)

www.bmw-m.net/TechProc/bleeder.htm

Mine hooks onto the brake reverse solenoid return tube into my master.

I bleed my brakes in under 5 minutes.

 

[oldjeep]

Re: bleed brakes?

OK. My trailer doesn't have a solenoid, it's a small trailer with a manual/mechanical lockout.

 

[dockwrecker]

Re: bleed brakes?

Buy a spare master cap, knock a hole in the top of the old one, thread a 1/4 NPT hole in the top of it, install a 1/4" barb fitting. Take a dab of silicone and seal any vent holes from the inside that it may have. Screw it on. Hook the pressure pump up to that. Done.

 

[This_lil_fishy]

Re: bleed brakes?

I got lucky, didn't have to bleed mine after all. Just had to adjust the brake so that the shoe could actually touch the drum.

Argh...a brand new trailer. Brake reservoir cap leaked, left wheel bearing loose, bad ground for all lights, brakes adjusted about 1/4" from the drum. Glad I checked and repacked the bearings for the season..always wondered why my boat seemed so heavy when trying to stop...now I know!

/rant
/hijack


Anyhow those pressure caps seem like a good idea, gonna give it a try. Thanks for the tips. Sorry to the OP for hijacking...


Ian

 

[jmfrost]

Re: bleed brakes?

Buy a spare master cap, knock a hole in the top of the old one, thread a 1/4 NPT hole in the top of it, install a 1/4" barb fitting. Take a dab of silicone and seal any vent holes from the inside that it may have. Screw it on. Hook the pressure pump up to that. Done.

This is what I was looking for! Is there a limit on the PSI of air to use or should I use something other than an air compressor?

 

[bruceb58]

Re: bleed brakes?

You typically can pump the master cylinder but it will depend on the type actuator you have.

Another way is to use a vacuum bleed method with a pump.

 

[dockwrecker]

Re: bleed brakes?

Just pump up the sprayer about 15 times until it flows steadily, doesn't take that much pressure, maybe 15 PSI.

 

[Stachi]

Re: bleed brakes?

After much trial and error this is what I ended up doing, by myself. I have a tandem axle trailer with disc brakes. Feel free to adapt to your circumstance.

I attached a tube to the bleed screw at the last caliper in the brake line. This tube was attached to a bottle and submerged in a small quantity of brake fluid.
Do not "crack" the bleeder, yet.

Next I coupled the tow vehicle to the trailer, attached the wiring. Opened the cap on the master cylinder of the trailer, topped off the fluid. Block the wheels to keep the trailer from backing up.

I then gently reversed the tow vehicle to compress the surge actuator, put the transmission in park, applied the park brake. This maintained pressure on the trailer's master cylinder.

I then went to the bleeder with the tube attached and "cracked" it open, allowing the fluid and bubbles to flow until no bubbles present. Closed the bleeder.

Went back and topped off the fluid in the master cylinder, and repeated the process until no more bubbles were present. Just because I am anal, after repeating the process on each of the other calipers, I did it all again..

The brakes work great now.

A couple points of interest:

If you have disc brakes you must make sure the trailer wire is attached to the tow vehicle to make sure you bleed the solenoid during this process.

I made a "pressure bleeder" so as to be sure I had a continuous flow of fluid to the master cylinder. This enabled me to actually drop the trailer tongue to the ground allowing me to use gravity to raise the bubbles in the line to the rear.

Hope this helps. There will be others with easier methods I am sure.

Bob

nice job bro,... you are a bubble chaser ( military term for a hydraulics mechanic)

 

[bruceb58]

Re: bleed brakes?

I then gently reversed the tow vehicle to compress the surge actuator, put the transmission in park, applied the park brake. This maintained pressure on the trailer's master cylinder.

I then went to the bleeder with the tube attached and "cracked" it open, allowing the fluid and bubbles to flow until no bubbles present. Closed the bleeder.

Went back and topped off the fluid in the master cylinder, and repeated the process until no more bubbles were present. Just because I am anal, after repeating the process on each of the other calipers, I did it all again..

Curious...how many times did you do this? You actually went into your truck and went forward and backwards multiple times?

 

[Bob's Garage]

Re: bleed brakes?

Curious...how many times did you do this? You actually went into your truck and went forward and backwards multiple times?

I had originally used the pressure bleeder to bleed the brakes, gauge read 20psi by the way, but didn't realize that I needed to bleed the solenoid so I was still having an air problem.

Once I determined that the problem was the operator not purging the solenoid, I hooked up the truck. That was when I decided to use the truck to depress (pump) the actuator. With the pressure bleeder keeping fluid in the reservoir I only backed the truck up the one time. I didn't need to pump the brakes (repeatedly back and forward) as the bleeder line was in the catch bottle, and I was back there cracking the valve releasing the bubbles. No air could enter the lines as the fluid in the catch bottle acts as a block to any reverse movement of air, instead, it would suck fluid into the line.

By the way, only moved the truck back less than an 2" to depress the actuator, then put the transmission in park and turned off the engine. Never any question about safety as the truck nor the trailer was going any where.

This method, although not normally used, is a lot easier than trying to pump the actuator by hand. Using the pressure bleeder is by far the easiest and quickest method and using the catch bottle, properly constructed, makes it a 1 man operation, about 10/20 minutes and no sweat.

 

[Bob's Garage]

Re: bleed brakes?

Curious...how many times did you do this? You actually went into your truck and went forward and backwards multiple times?

I had originally used the pressure bleeder to bleed the brakes, gauge read 20psi by the way, but didn't realize that I needed to bleed the solenoid so I was still having an air problem.

Once I determined that the problem was the operator not purging the solenoid, I hooked up the truck. That was when I decided to use the truck to depress (pump) the actuator. With the pressure bleeder keeping fluid in the reservoir I only backed the truck up the one time. I didn't need to pump the brakes (repeatedly back and forward) as the bleeder line was in the catch bottle, and I was back there cracking the valve releasing the bubbles. No air could enter the lines as the fluid in the catch bottle acts as a block to any reverse movement of air, instead, it would suck fluid into the line.

By the way, only moved the truck back less than an 2" to depress the actuator, then put the transmission in park and turned off the engine. Never any question about safety as the truck nor the trailer was going any where.

This method, although not normally used, is a lot easier than trying to pump the actuator by hand. Using the pressure bleeder is by far the easiest and quickest method and using the catch bottle, properly constructed, makes it a 1 man operation, about 10/20 minutes and no sweat.

P.S: I also made a pressure system for changing the lube in the lower units in my outboards. Used the same type garden sprayer (not the same one) with the parts from a "lube pump" and it works great with almost no mess. Takes longer to drain than to fill with better control.