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-   -   Trailer brakes locked up...Need Help - Pics (http://www.wakeworld.com/forum/showthread.php?t=795980)

QuickVR4 10-22-2012 4:46 PM

Trailer brakes locked up...Need Help - Pics
Trailer was fine and backed it into my driveway. Now that it is time to get the boat out, the brakes are locked. Trailer will roll freely in reverse, but locked in forward. Friend said to flip plug and that would release brakes, but that did not work. Had trailer for a year and this was never an issue. Help, I need to get my boat winterized!!!!!!!!!!!!

Here are some pics I took. Plug has always been missing 4th prong without issue as you will see in pic.





10-22-2012 7:38 PM

The same thing happened to an old boat trailer I had. If they are drum brakes, I bet some springs broke and allow the brake shoes to open up. I raplaced the whole brake assy and it fixed the problem.

boardman74 10-23-2012 5:10 AM

Flipping the plug isn't going to do anything since that looks to be a full mechanical surge setup and doesn't have the lockout solenoid. Odd that it works in reverse and locks in forward, its usually the opposite. Make sure the tongue actuator is pulled forward. Sometimes if they are left back the will get stuck. But if thats the case the brakes should be stuck both directions.

boardman74 10-23-2012 6:14 AM

Also does the actuator part of the tongue move freely in and out. Probably won't be able to move it by hand. Use a 2x4 as a lever and push it in and out to make sure it's free. If your not familiar with this you loop your safety chains together and slide the 2x4 thru the chains and against the front of the tongue. Then when you pull the 2x4 toward the rear the chains stop the bottom and it will push the actuator part of the tongue into the rear.

Alot could be wrong. How long has it been sitting? Check the lines, check the brakes on the wheels, check for fluid in the master cylinder.

osukellen 10-23-2012 7:35 AM

Emergency brake cable might have gotten pulled somehow.

boardman74 10-23-2012 9:41 AM

Nope. You can see in the first picture the lever is in the free position, not pulled for the E-brake.

beerguy 10-23-2012 12:35 PM

I had a master cylinder freeze up with the same result. Could go backwards but couldn't budge it forward. I have a removable tongue so disconnected the quick connect on the brake line to free up pressure so I could move it.

phatboypimp 10-23-2012 1:24 PM

If you need to get it on the road for the winterization - and you have a big enough tow rig to not need the brakes - I would release the pressure at the backing plates/calipers like you do when you are bleeding the brakes. That should release the pressure and let you get on the road. If it doesn't it will tell you that the problem is likely with the backing plates/calipers. These actuators fail pretty regularly. I imagine it is time for a rebuild.

bftskir 10-24-2012 6:48 PM

you can see fluid in the pics leaking all over

srock 10-25-2012 7:56 AM

Another trailer failure....again and again the simplest piece of equipment is the biggest piece.

john211 10-25-2012 2:04 PM

My trailer's brakes locked in forward when my surge system went bad. Yeah we bled the lines at the brakes just to get home.

I did some tests to see if I could figure what was wrong. The solenoid worked. When tested, I could definitely hear its click and feel its throw.

I just had everything replaced. After that, I conducted an autopsy on the failed parts. What I suspect now is that, the solenoid has a pinhole aperture that must be open, and that the right size of contaminant clogged it and disabled the solenoids function.


The system works kind of like this. It is an auxiliary brake pedal. When you brake your tow vehicle, the momentum of the boat and trailer pushes into the tongue, causing the ram of the surge-brake cylinder to depress into the the surge-brake cylinder. It is like the boat and trailer are stepping onto an auxiliary brake pedal, which applies braking to the trailer brakes.

When you back up the trailer, you again cause the ram of the surge-brake cylinder to depress into the the surge-brake cylinder, which in the absence of a counter-action is going to cause the application of braking to the trailer brakes. The counter-action is the the switching ON of the reverse lights. If the reverse lights are switched ON, the solenoid is likewise energized, and it opens a bypass loop from the output of the surge-brake cylinder to a reservoir of brake fluid for it, which is behind it (in the brake loop ... on mine, the reservoir is actually immediately on top of the surge-brake cylinder ... in the same housing).

When I did my autopsy, I found that the aperture in the solenoid for the bypass loop is teeny ... again ... the size of a small pinhole. I imagine it was at risk of being stopped easily by rather small contaminant particle(s).

The reservoir Tees into the cylinder by an (a final) aperture in the middle of the axial length thereof. When the plunger commences plunging, it first just pushes brake fluid into the reservoir. Once the plunger closes the aperture to the reservoir, pressure is applied to the brakes. When the trailer is pulled forward, that sliding axial pin you see in your trailer (and which you lockout with nuts or coins and the like) is actually just locking out a shock absorber. It appears that the force which returns the plunger to the extended position are a pair of springs ... the heavy duty work probably being done by the red one, given its size relative the little wire spring.

When my system was contaminated, I imagine the following happened. It agrees with the sequence of things.

It was getting difficult to back up my trailer. My brakes were constantly braking while backing up. I believe the bypass aperture was clogged. So, several times I just gunned my tow vehicle in reverse, causing the tires to sort of bounce or otherwise break free a little. What I was doing was causing the plunger to travel past the last aperture to the reservoir. Once I did that, and with the bypass aperture being clogged and allowing no bypass flow to the reservoir, I had my plunger stuck by the incompressibilty of the brake fluid. The springs could not supply sufficient 'break free' force to push the plunger back behind the last aperture to the reservoir against the 'hold-fast' tightness of the plunger being jammed past the normal travel it should travel in the cylinder.

Disclaimer. This is the Internet ... where everyone is smarter than everyone else. Don't come back and tell me all it took was a rap with a hammer (which might not be a bad idea).

john211 10-25-2012 2:19 PM

Also ... for anyone who never read posts on technical matters from Bocephus - Sam Ingram - Tucker McElroy ---

his posts were worthwhile ... to say the least.

srock 10-26-2012 9:51 AM

Mine does not have springs to snap it back or I should say if it does they are not big enough. It takes the pull of the vehicle to spring/pull the actuator forward.

In reality we should all be replacing the fluid in our lines every few years as brake fluid is attracts contamination relatively fast.

john211 10-26-2012 12:47 PM

I think you misunderstand the work of the return spring. Yes, it takes the pull of the vehicle to pull the forward sliding part of the tongue AWAY FROM the rest of the trailer and boat.

But the little wire return spring in the cylinder against the grey plunger is what returns the grey plunger to its 'home' position. This is the same way the master cylinder works in the tow vehicle. After the driver takes his or her foot off the brake pedal, the plunger in the master cylinder is likewise returned to its 'home' position by a pair of return springs -- and not some extraordinary pull or push force from some source other than the return springs.

So it is with the cylinder in your trailer tongue. If the plunger is stuck in it ... and keeping pressure to the trailer brakes and hence keeping them braked ... no amount of pull by the tow vehicle and forward tongue as one unit AWAY FROM the rest of the trailer and boat as another unit are going to pull that push rod out of the cylinder to pull that plunger forward.

In my pictures, when the gray plunger is pushed rearward from its 'home' position by the push rod, braking pressure is applied. When the forward part of the tongue is pulled forward again, pressure is released on the push rod. But, it is that little wire spring which is inside the cylinder that pushes the plunger back to the home position.

Again, that plunger can easily get stuck against the light pressure of that spring.

john211 10-26-2012 5:59 PM


Here's information on how a tow vehicle's brake system and master cylinder work. I link this because it looks worthy of wakeworld and/or any brand specific site for wake boat owners.

I like this guy's doggedness.

"With the wrenches, I had to modify them so I could get them to be thin enough, be the right angle to get around the pedals, and to stay on when I wasn't actually holding them. A grinder, a Dremel, and a torch were needed."


"When the pedal is released all the way, the return springs push everything back home again. "
* * *
"When you brake, the fluid heats up, both from the act of compression, and from heat generated by the friction surfaces. This causes the fluid to expand, so the volume of fluid after braking is larger than it was before braking. The excess volume is vented through the intake/return ports when they reopen, allowing the wheel pistons to move back home and release pressure on the discs/drums."

And so on.

When I realize now that a driver's foot pressure on the push rod is being replaced by the full weight of a loaded boat and trailer, I appreciate better the following. There is no driver 'feel' for when things in the trailer plunger and seals are beginning to deteriorate. And, the ultimate force which wrecks things is exponentially far greater.

Iceberg 10-27-2012 10:00 AM

John211 is bang on. From the oil in OP's picture, the piston assembly is shot. One way to get into trouble with your surge system is to back up too quickly from when you put it in reverse! Give your solenoid time to open before backing and go slow until the cylinder is compressed.

john211 10-27-2012 10:54 AM

Now that I've had time to mull over that long article, here is one problem I never appreciated before.

In Part 5, "How the Master Cylinder works, and why the pushrod needs to be set correctly," he says,

(I never saw his name, but he mentions he's Canadian).

"Adjustment of the pushrod is critical!"

"If the pushrod is misadjusted too tightly, and never allows the seals to move rearwards enough to uncover the return ports properly, your brakes will slowly lock on more each time you brake, eventually bringing the car to a stop."

In Part 7, he steps through his procedure for adjusting pushrod freeplay in his 1991 Acura.

But ... to me ... it appears to be a really challenging task that I personally might not attempt. The author even forewarns as much in his opening statement:--

"I don't think Honda really wants you messing with pushrod adjustment. Otherwise why would they have made it so cryptic?"

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