Replacing brake lines

truckermatt · Mar 24, 2012

Last year I changed my Master cylinder on my surge drum brake trailer. because it would leak brake fluid. Well the leaking stopped, but i still have no brakes.

I bleed the brakes after install,, and some fluid did come out but was a brown rusty sludge type. So now I want to replace the brake like and start fresh, the previous master cylinder was leaking for years before i bought the boat.

I see kits that have flexible rubber lines, do they hold up well.
http://www.easternmarine.com/20-single-axle-disc-drum-flexible-brake-tubing-kit-80326

Currently I have a steel line from MC that runs inside frame channel and down the axle, then splits off to each wheel.

I want to keep it simple, and I have never installed brake lines before. I dont have flare tools and such.

Would you go with flex line or get steel line again ?

calvinator · Mar 24, 2012

Re: Replacing brake lines

I just bought that exact kit and it installed easily and is high quality stuff. Flex lines for me. Any extra slack you just secure to the frame of trailer.

Just double check your brake wheel cylinders too. If those are trashed too, you can just buy a whole new brake kit w/flex lines and have all new parts. I went the other way -- piece by piece, hour by hour -- and wish I just went with all new stuff.

truckermatt · Mar 24, 2012

Re: Replacing brake lines

what would i look for when checking the wheel cylinders? are they are to replace?

ricohman · Mar 24, 2012

Re: Replacing brake lines

You need wheel cylinders. Unless the lines are rusted though I would run them. If you are going to replace them I would also go with hard lines. Long flex hoses = less pressure at the cylinders. Flaring lines is not difficult and you can buy brake line anywhere.
Brake fluid is hygroscopic so it really should changed every couple of years in applications that have small volumes. Like a boat trailer.

Sabbath · Mar 24, 2012

Re: Replacing brake lines

truckermatt said:
what would i look for when checking the wheel cylinders? are they are to replace?

You want to check to make sure they arent leaking past the seals.

Outsider · Mar 24, 2012

Re: Replacing brake lines

I bleed the brakes after install,, and some fluid did come out but was a brown rusty sludge type.

Did you bleed the master before installing? Take it to a tire shop with a vacuum bleeder, best money I ever spent ...

truckermatt · Mar 25, 2012

Re: Replacing brake lines

Outsider said:
Did you bleed the master before installing? Take it to a tire shop with a vacuum bleeder, best money I ever spent ...

I didnt know you could bleed a new master cylinder?

rickryder · Mar 25, 2012

Re: Replacing brake lines

Bleed it by cracking the line loose at the master cyld.

Flare tool most be for double flare for brake lines...

ricohman · Mar 25, 2012

Re: Replacing brake lines

truckermatt said:
I didnt know you could bleed a new master cylinder?

Always bench bleed any master before installing it. And as mentioned above you need to know how to double flare the lines. Its not difficult but if you have any doubt get a mechanic to do it as you want a safe trailer. As a mechanic I have seen horrible sludge in brakes and lines but I have only replaced a handfull that were rusted to the point of being unsafe for a trailer.

bruceb58 · Mar 26, 2012

Re: Replacing brake lines

Replace your wheel cylinders and use stainless steel brake lines.
http://www.championtrailers.com/brkparts.html

The statement about long flex hoses = less pressure is incorrect. It is true that the master cylinder will need to pump a larger volume of fluid to compensate for the slight rubber flex, the pressure will end up being the same as the way surge brakes work, the surge mechanism will compensate for that. I would still prefer stainless steel brake lines though.

I do agree with the comment that brake fluid should be changed every other year. I do that in my vehicles as well.

ricohman · Mar 26, 2012

Re: Replacing brake lines

bruceb58 said:
Replace your wheel cylinders and use stainless steel brake lines.
http://www.championtrailers.com/brkparts.html

The statement about long flex hoses = less pressure is incorrect. It is true that the master cylinder will need to pump a larger volume of fluid to compensate for the slight rubber flex, the pressure will end up being the same as the way surge brakes work, the surge mechanism will compensate for that. I would still prefer stainless steel brake lines though.

I do agree with the comment that brake fluid should be changed every other year. I do that in my vehicles as well.

Long brake hoses swell under pressure. Thats why there are millions of cars and bikes with steel braided lines swapped in and engineers strive to make the flex hose as short as possible. I've installed hundreds of steel braided flex hoses on older bikes and to say braking was improved is an understatement. Sure you can continue to squeeze the brake harder to make up for the hoses swelling and pressure at the calipers (or wheel cylinders on a trailer) reducing. But if the system is properly designed you won't have to. With small volumes of brake fluid, sometimes this isn't even an option.
Keep the flex portion as short as possible.
http://www.hotrodheaven.com/tech/brakes/

bruceb58 · Mar 26, 2012

Re: Replacing brake lines

I agree with you, they swell under pressure but eventually they achieve the pressure. Surge brakes already have a long lag assosciated with them and the rubber brake lines add a little more to it. The brake master cylinders have plenty of volume to compensate for the slight swell especially on a disc brake system.

Main reason you don't want them on a car/bike is that you don't get that immediate braking response and your pedal/lever feels soft as you apply the brakes. Not necessary for a boat trailer and that is also a reason some trailers come from the factory with them. I prefer stainless lines anyway for the durability aspect.

Mikeyboy · Mar 26, 2012

Re: Replacing brake lines

If you do use line verses hose a lot of auto parts stores rent flairing tools so you don't have to buy a tool you will probably never use again.

ricohman · Mar 26, 2012

Re: Replacing brake lines

bruceb58 said:
I agree with you, they swell under pressure but eventually they achieve the pressure. Surge brakes already have a long lag assosciated with them and the rubber brake lines add a little more to it. The brake master cylinders have plenty of volume to compensate for the slight swell especially on a disc brake system.

Main reason you don't want them on a car/bike is that you don't get that immediate braking response and your pedal/lever feels soft as you apply the brakes. Not necessary for a boat trailer and that is also a reason some trailers come from the factory with them. I prefer stainless lines anyway for the durability aspect.

Yes.
But your original stament "long flex hoses = less pressure is incorrect" is only correct if compensation for the reduced pressure can be applied with additional force at the MC.
The pressure applied at the MC will be always be less at the wheel. And long flex lines will further reduce this. I agree with you, but if someone wanted to run 8 ft flex lines I don't think I would

lncoop · Mar 26, 2012

Re: Replacing brake lines

This reminds me of a question I meant to ask but never did. There's a fitting that goes between my MC and the first short section of brake line. It has a tiny orifice, 1/64" I believe, in the end. It was so traumatized from my previous encounters with it that I ended up having to order a replacement (not available anywhere in town of course), but I started wondering what the implications would be of no longer using it and simply screwing the short piece of brake line directly into the back of the MC. Is that little orifice designed to restrict the flow so your brakes don't lock up, or what? Sorry for the hijack.:redface:

ricohman · Mar 26, 2012

Re: Replacing brake lines

lncoop said:
This reminds me of a question I meant to ask but never did. There's a fitting that goes between my MC and the first short section of brake line. It has a tiny orifice, 1/64" I believe, in the end. It was so traumatized from my previous encounters with it that I ended up having to order a replacement (not available anywhere in town of course), but I started wondering what the implications would be of no longer using it and simply screwing the short piece of brake line directly into the back of the MC. Is that little orifice designed to restrict the flow so your brakes don't lock up, or what? Sorry for the hijack.:redface:

Without seeing it I would guess that this is a residual valve. They have various uses for discs and drums and the location of the MC. They are also offered with different PSI for different applications. I believe the low PSI are for discs and high PSI for drums to prevent air getting into the cylinders and to maintain pressure.
This can be an important piece on a trailer. And if you have drum brakes you definately need it.

lncoop · Mar 26, 2012

Re: Replacing brake lines

This is it.
http://www.google.com/products/cata...=X&ei=IplwT-2eDYfk0QGtwtjwBg&ved=0CEgQ8wIwBA#

bruceb58 · Mar 26, 2012

Re: Replacing brake lines

ricohman said:
The pressure applied at the MC will be always be less at the wheel.

The static pressure will always be the same. That is why it doesn't matter. If you have a pressure gauge at the MC and at the wheel cylinders you will measure the same. Just like you would with a rubber garden hose at home with no water running through it.

The residual valve is part of the master cylinder and is not seperate fitting. The residual valve is only used by drum brakes to keep a small amount of pressure built up in the lines at all times. You can't use one with disc brakes at all because it will cause the brakes to drag.

The fitting you are describing is typically only an adapter with an orifice to control how fast the fluid flows out of the mater cylinder but it does nothing regarding holding any residual pressure. It acts somewhat as a fluid damper. You definitely need it. If it wasn't there, you would have oscillationsduring the braking.

If the OP has an enclosed tubing trailer and plans on running lines through it, I would not run steel or stainless steel lines through it. I would definitley use the flex lines in that case. The problem is that the lines aren't supported in the tube so they are constantly wearing against the tubing because of the vibration. Add the extra problem of rusting if steel lines are used.

ricohman · Mar 26, 2012

Re: Replacing brake lines

bruceb58 said:
The static pressure will always be the same. That is why it doesn't matter. If you have a pressure gauge at the MC and at the wheel cylinders you will measure the same. Just like you would with a rubber garden hose at home with no water running through it.

The residual valve is part of the master cylinder and is not seperate fitting. The residual valve is only used by drum brakes to keep a small amount of pressure built up in the lines at all times. You can't use one with disc brakes at all because it will cause the brakes to drag.The fitting you are describing is typically only an adapter with an orifice to control how fast the fluid flows out of the mater cylinder but it does nothing regarding holding any residual pressure. It acts somewhat as a fluid damper. You definitely need it. If it wasn't there, you would have oscillationsduring the braking.

If the OP has an enclosed tubing trailer and plans on running lines through it, I would not run steel or stainless steel lines through it. I would definitley use the flex lines in that case. The problem is that the lines aren't supported in the tube so they are constantly wearing against the tubing because of the vibration. Add the extra problem of rusting if steel lines are used.

Thats incorrect. Many disc systems run residual valves. These systems needed the 2 psi or so to maintain pressure. And not all of them are part of the master. You can even buy stand alone residual valves.
Most drum MC's have the residual valve built in. But you can modify a drum MC to run discs by removing the valve and installing a 2psi valve separate from the MC. If the the MC is at the level of the calipers or lower you need the residual valve anyway.
Lots and lots of older cars and trucks with disc brakes had residual valves. Most now use a proportioning valve or a combination of.
I've added many residual valves to the disc systems of custom cars and trucks. Usually a 10 out back and a 2 up front.

Long rubber lines (not braided steel), cheesy calipers, cheap thin drums can all lead to loss of braking force.

bruceb58 · Mar 26, 2012

Re: Replacing brake lines

Boat trailer disc brakes do not use residual valves. I know they are available for motorcycles. Thats more of an issue because the mastercylinder can be lower than the brakes.

Residual valves on trailer brake master cylinders are located in the master cylinder. I have seen a lot of Trailer mastercylinders over the years and yet to see the external type.

We are talking about boat trailers here. Not automotive or motorcycles. None of the trailer disc brake manufacturers allow the use of residual valves. All of them have that statement in their directions. Please let me know if you know of any trailer disc brake manufacturer that states you can use them.
http://www.championtrailers.com/remove_residual_valve.htm

Here is from the instruction manual for Kodiac disc brakes:
http://www.kodiaktrailer.com/images/pdf/man-installation.pdf

3. No Residual Line Pressure - The older hydraulic drum brake systems require
that a 10 - 12 psi residual pressure be maintained in order to keep the wheel cylinder
piston seals seated. To accomplish this, many surge brake actuators have a small
diaphragm type check valve installed just inside of master cylinder output port.

5. Disc brake systems must not be subjected to any residual brake line pressure (it
will overheat the brakes and hubs). Therefore, make sure (1) you are using a surge
brake actuator that is designed specifically for disc brake applications, or (2) that the
diaphragm check valve on the drum brake version is rendered inoperative (an ice
pick or awl can be used to perforate the diaphragm).

Replacing brake lines

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