Hydraulic Trailer Brakes not releasing - need help

[The Poacher]

Hey Raiders,

Hoping you can help. I used the boat Monday and parked it as usual. Put the park brake on (manual lever) and all was fine. Went to drive away today with the boat on the car, and the car wouldn't move!!! Even under power, it didn't move forwards or backwards. The trailer brakes are jammed on, so there must be a problem with the brakes not releasing. Can anyone point me in the general direction of help??

Thanks

The Poacher

Edited December 30, 2014 by The Poacher

[zmk1962]

Need a bit more information. I have a twin bogey trailer with an electric hydraulic set up with 4 hydraulic disc brakes. I have had on rare occasions individual calipers (usually only 1 out of the 4) seize due to the caliper hydraulic cylinder jamming while open. Bit of WD40 and levering of the calipers usually pries the calper open enough or frees them up enough to get back home. The cause vaires - may be gunk or rust buildup etc or just time for an overhaul of the hyrdaulic brake seals etc etc.

But in your case, I am not sure if ALL your brakes have locked up - in which case your problem may be further up at the master hydraulic unit etc. Can you describe your system, what drives the hydraulics (over ride, electric, compressed air) and if all your brakes are jammed or just some?

[The Poacher]

Hi ZMK,

Its a single axle trailer with over ride brakes - no electrics involved at all. So I think its the master hydraulic unit, as you have guessed.

I put a fair bit of pressure on from the car, and it didn't move an inch - so I think that both wheels must be locked. Also, I took the lid off the brake fluid reservoir and the level stays the same whether the brake lever is on or off - so it seems that the master unit is stuck or broken.

I am pretty useless mechanically, so I wouldn't know where to start trying to fix it? I tapped it with a hammer to see if I could loosen it up. Any suggestions would still be welcomed.

Thanks

[zmk1962]

There must be a way to ease off the hydraulic pressure (worst case you could undo the bleed nipple on each of the brakes but you will lose hydraulic fluid) - what brand/model isyour master cylinder? I'll see if I can google the manual for it and check.

Also sent you a pm with my mobile number.

[Fab1]

Hi mate,Sounds like you have disintegrated master cylinder piston cup rubbers clogging up the realease port in the master cylinder which will hold pressure in the system even with the hand brake lever released.

When the brakes are applied the master cylinder fluid should drop slightly and raise slightly when released.

The easiest way to check if this is indeed the case is to disconnect the steel brake line from the master cylinder or the wheels which should relieve the pressure from the system thus releasing the brakes.

Wrap a rag around the line once removed to soak up any drips.

If the brakes have released once you've done this at best you will need to rebuild the master cylinder if parts are available and at worst buy a new one.(Not many people rebuild master cylinders and wheel cylinders anymore).

If the brakes are still holding after doing the above mentioned the problem usually is either seized calliper pistons or slides.

A lot of problems with the braking systems especially on boat trailers is caused through neglect as in my opinion brakes dunked in to salt water on a frequent basis need constant attention and even more if used less frequently.

Considering you don't have the mechanical knowledge it will be in your best interest to give the job to someone like Huey as when mistakes are made with brakes they can bite you once and hard.

Lastly always replace your brake fluid regularly to keep it fresh as it goes a long way to preventing issues.

Cheers.

[zmk1962]

Ok.. Fab! has given you how to releive the pressure. I see you've added a picture. Was able to grab from that the web address...

Here is the master cylinder part that looks like yours: $43.95 RRP ...At that price i'd just replace it.

http://www.astss.com.au/CatalogueRetrieve.aspx?ProductID=5898211&A=SearchResult&SearchID=42040356&ObjectID=5898211&ObjectType=27

[batfishing]

How mechanical are you?

I can possibly talk you through backing it off but you won't have any brakes.

Either the master cylinder has jammed back, or the wheel cylinders have locked on.

Someone has previously suggested backing off the bleeder screws. Good place to start.

At the wheels, you will see the brake unit. Coming into that is a pipe, a short distance from the where the pipe screws in, maybe 20mm or so will be a bleeder screw, loosen/remove these screws (one per wheel) by turning them anticlockwise.

It is best to use a ring spanner and ensure it is a very good fit. Preferably soak it with WD40 or similar before you try to loosen it. Unfortunately on boat trailers they rust in.

If you can get them out, that will release the hydraulic pressure, if the master cylinder is the problem.

Try moving it then and see if it releases the brakes.

If not, then it's Jack it up and wheels off, make sure you put safety stands under the trailer or solid blocks of wood, NOT bricks, before you work under the trailer. I also place the wheels under the trailer frame, keep legs etc out from under the frame.

Remove the brake lines from the caliber. There should be two bolts securing each brake calliper from the rear, into the axle, remove those, turn bolts anticlockwise.

Then large screwdriver, lever, hammer, prise the whole caliper and brake pads UP, off the disc.

As I said you will have no brakes, but will be towable taking care to your mechanic

Sent from my iPad using Tapatalk HD

[The Poacher]

Thanks Raiders,

Really appreciate the effort you put into answers. I have worked out a solution, and will be able to continue fishing the holidays. It never ceases to amaze me the collective knowledge out there, and the willingness of people to share it.

As I said, really appreciate the help,

Cheers and Merry Christmas to all,

The Poacher.

[Floating_Medic]

Thanks Raiders,

Really appreciate the effort you put into answers. I have worked out a solution, and will be able to continue fishing the holidays. It never ceases to amaze me the collective knowledge out there, and the willingness of people to share it.

As I said, really appreciate the help,

Cheers and Merry Christmas to all,

The Poacher.

And the solution was??

I would have just thought it was sticky pads that may have rusted slightly to the discs so was going to suggest a simple bit of tapping with a metal head hammer on the pads themselves. I used to get this a bit with my trailer but they were mechanical not hydraulic and it turned out that the springs to pull the pads back off the discs were just a little old and a bit of tapping used to get them going every time.

[Lonx]

Hmm with hydraulic... If they are locked on, I'd first check for surface rust fusing the disc but if your car can't break that, I sure wouldn't be driving that boat behind it as any tow vehicle should unless your brakes are completely stuffed! Then try a bleed from both callipers to prove there is no line blockage. Last would be to remove the particular locked caliper as a split seal can jam them, however it is very rare.

I know you said this happened within a few days so surface rust lock is quite unlikely. What did you find it to be?

Edited January 2, 2015 by Lonx