View Full Version : Trailer master cylinder does not maintain fluid level

Cigars n scotch
06-23-2014, 11:34 AM
I have a question that I know nothing about.

I will disclose that in April I bled my brake lines with the help of my dad and refilled. I had to change out a leaky seal which meant repacking all bearings and such.

For some reason my master cylinder on the trailer tongue is sucking brake fluid, it seems like I have to refill it every time I go out. This worries me because I am driving a 3 hr trip this weekend to camp at J. Strom Thurmond Lake.

There are no leaks, why would the brake fluid keep emptying?

06-23-2014, 12:02 PM
Because there is a leak.

06-23-2014, 12:26 PM
Second that. I just redid all mine and a new actuator as well. Fluid shouldn't go down at all really unless your pads are wearing and the calipers have to compress further to compensate. But that is more slowly over time. You're definitely losing fluid somewhere.

06-23-2014, 01:06 PM
Because there is a leak.

http://i279.photobucket.com/albums/kk143/faeini1/MJZ409.gif (http://media.photobucket.com/user/faeini1/media/MJZ409.gif.html)

I only posted the above since you beat me to that reply!

06-23-2014, 01:26 PM
That's OK. We're used to you being a little slow. That's why they sent that special short bus for you every day.

06-23-2014, 01:29 PM
meh, this is the only short bus I ride:


06-23-2014, 01:31 PM
That's a cool name for a board. Very memorable.

Cigars n scotch
06-23-2014, 01:32 PM
Leak you say? Hmm, I see no leaks but I will just have to look harder I guess.

Leak in the lines?
Leak in the nipple? (Well maybe for a breast feeding mother)
Leak in Seal?
Leak where else am I forgetting?

06-23-2014, 06:52 PM
1- under the tongue - where the line goes into the actuator/master cylinder. If it's dripping from there you many never see it if it's when you're going down the road.

2- all T-splits where the lines go off to other wheels

3- each of the calipers where the line goes into it

4- bleeder vales - are they tight?

5- caliper itself leaking may be tricky to detect...

Break fluid is usually really good at removing paint so look for any thin spots or rust. There are some vids on youtube about how to manually bleed your breaks by using a screwdriver to pump up the actuator's master cylinder.

That may also work to look for any leaks when under pressure. Search for "Asian Bass Guy Break Bleeding". He does a decent job of showing and explaining the parts and steps although they can be lengthy.

Basically pump it up into a pressurized state (brakes on) and go around looking for wet spots.

Cigars n scotch
06-23-2014, 07:52 PM
Ok so here is where I am at after looking some more at the the lines and all. I can see no visible sign of a leak on the t splits, each caliper, bleeder valves are tight, seals are good. Haven't checked the caliper itself by removing the wheels but I gave a good look all around and didn't see any fluid.

I did notice though that after removing the reservoir cap that the fluid had gone down a little it since filling it last night, so it leads me to believe that there's a leak on the master cylinder but I know under the tongue where the line goes into the actuator it is not leaking as far as I can tell. There is "wetness" underneath there but I am not sure if it's from fluid that I spilled while filling as I did spill a little bit. I wiped everything down to dry it off as much I could so I will check it tomorrow again. I did notice that underneath the tongue right in the open spot where the solenoid is there's a little paint that is peeling away, again not sure if this is spilled fluid or leaking.

I have a hunch "maybe" the master cylnder is leaking but not positive. I'll keep an eye on it and report back tomorrow if I notice the fluid level down again. (the trailer hasn't moved)

Thanks berg for the pointers.

06-24-2014, 09:46 AM
Happy to help man.

How about setting out a piece of cardboard or paper under it overnight to see if you catch any drips. Dropping level while just sitting there sounds like a serious leak! Did it ever feel like the trailer was pushing you through a stop?

Cigars n scotch
06-24-2014, 10:00 AM
Well it is indeed a leak in the master cylinder! ugh!! I left a paper towel on the garage floor overnight and there's a round ring of fluid, drips, on the paper towel. Not what I needed right now.

I've never felt the trailer pushing my truck through a stop though.

I am thinking that this cause is a result of an incident that happened last fall that I posted about when I accidentally forgot the tongue swing pin and when I came to a stop the whole tongue jack-knifed into my bumper.

Now I am going to have to pull the inner member and diagnose leak cause, get replacement parts and fix and then bleed my brakes AGAIN which I HATE to do.

Oh and I have seen that Asian Bass guy video before, it's actually the one I watched to try and learn how to bleed the brakes the first time I did it back in April.

06-24-2014, 10:19 AM
Glad you found it. I'm sure you are frustrated but working brakes are worth the effort.

Cigars n scotch
06-24-2014, 10:52 AM
I'm looking online at Pacific Trailers now. My trailer has disc brakes correct? Trying to find the right replacement master cylinder for reference.

06-24-2014, 11:29 AM
Most likely this guy-

Or if you just wanted to gut it and start clean, this guy (if you have brakes on both axles)-

Cigars n scotch
06-24-2014, 11:43 AM
Berg that first link is the one I was thinking! Thanks!!!!!

I'm not sure if I need to gut it and start clean or not. Seems like a drastic solution.

I just looked at the picture of the bottom of the inner member replacement and noticed the reverse valve drain tube is pushed flush with the solenoid. Last night while working on mine I noticed there is a decent gap on my drain tube, it isn't sitting flush against the solenoid as pictured.

I wonder if that could be leaking? Though based off the positioning of the internal parts in that pic leads me to believe it's the master cylinder but I will check again.

Damn it why do I have to work!! I'd rather just be getting this out of the way.

I am thinking my camping trip this weekend is toast because of this f'ing mess.

06-24-2014, 11:56 AM
Yes, drastic but perhaps time saving. To do the whole inner member you knock out the 2 pins, disconnect the brake line, cut the solenoid wire, and yank it out. Less than 10 minutes if you have the right tools and don't have any rusty stuck parts.

New one goes back in in about the same amount of time. I can't say what it takes to pull the Master Cylinder out and swap for another. Mine was frozen solid and 13yrs old so I opted to gut it.

Cigars n scotch
06-24-2014, 12:42 PM
I may end up going this inner member route and seeing if I can have it overnighted.

How do you remove those retaining clips that hold the roller pins in so you can slide it out?

06-24-2014, 12:55 PM
Need a pliers like this to remove (spread apart) the snap rings on one side.


After disconnecting the wire & line then the whole thing should slide out the front.

Cigars n scotch
06-25-2014, 02:48 PM
Thanks Berg I figured it was those type of pliers. HF has them so I'll pick them up.

Ordered a new master cylinder and paid (out the a$$) for 2 day shipping so should be here tomorrow. Quick swap (hopefully) and bleed the brakes and I'll be ready for our trip. Nothing like cutting it close!!!

Cigars n scotch
06-26-2014, 03:33 PM

I can't unscrew the solenoid from the master cylinder, sprayed some penetrating lube on the threads but still no go. I am trying to swap out my master cylinder but OF COURSE it won't go smoothly.
Any ideas from the gurus? I've already wasted over an hour and a half. I need to get this done and get my brakes bled for tomorrow's trip so I am desperate.

Cigars n scotch
06-26-2014, 03:59 PM
Ok I got the solenoid off but the threaded screw stayed on the master cylinder and I can't figure out to to get this thing off. Any insight boys? If I had to could I get this at a hardware store?

http://i156.photobucket.com/albums/t39/newmanium/Trailer%20Axle%20Seal%20Replacement/E708A9CD-F1AD-40EC-9D51-049F475991E4_zpshxradulj.jpg (http://s156.photobucket.com/user/newmanium/media/Trailer%20Axle%20Seal%20Replacement/E708A9CD-F1AD-40EC-9D51-049F475991E4_zpshxradulj.jpg.html)

06-26-2014, 05:03 PM
Looks like a small pipe fitting. Maybe the plumbing section at Lowes.

Cigars n scotch
06-26-2014, 07:12 PM
My father said it is a nipple, and sure enough it was. lowes had them after I found out HD did not. Could only find brass though so used Teflon tape and was careful not to strip threads.

Let's tell you, whomever the f**k was the genius that decided the hose and fitting to screw into the solenoid is a got damn retard!!! This was the biggest pain in the ass as the hose just curls up as you're tightening it and creates just a mess! So stupid IMO.

But it's all put back together and I just have to bleed the brakes now.

06-27-2014, 10:26 AM
Glad to hear your progress is ongoing. Hope you can git er done.