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Brake issues, need input.

rlwm211

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When you operate the pedal the piston in the master cylinder moves forward. There is a small "vent" hole ahead of the piston that allows the last of the fluid pressure to return to the master when you release the brakes. I believe this is the fluid you are seeing bubble up when you push the brake pedal. The air is just that which is carried with the fluid as it squirts up under pressure out of the master cylinder main bore and out of the main resevoir.
I would use copper tubing and a compression to 1/8" pipe adapter on the end. The tubing is also 1/8". It does not need to be very big, and I would run it up and into the cab and make a loop to keep stuff from falling into the tube. you can also connect this to an external brake fluid resevoir which can be purchased online, or at speed shops. If you decide to mount a remote resevoir, you will want larger tubing or else filling the master will take a week.

RL
 
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WOLFMAN1

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did not know that. the manual i have on cd suggested something about breaking off the flat piece that extends from the filler cap on the inside to make it fill faster with the added resivor. thankyou. what are your thoughts on the filler cap breakoff.:deadhorse:
 

rlwm211

Active member
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Location
Guilford, NY
brakes and more fluid.

If I were going to use the original cap as an adapter for an external resevoir, I would do whatever it took to make the fluid move through it quickly. You may even consider drilling out the cap and tapping it for a larger pipe size, such as 1/4". (Take it off first of course) It is cast and pretty easy to work, and if you are at all handy this will not be difficult. It is very important to make sure your cap is sealed to the top of the master if you are going the route of an external resevoir.
The baffle inside the cap is there to try to stop the upflow of the fluid when you press the pedal. A test to see if the master is in fact healthy is to watch the fluid in the resevoir and press the pedal slowly, and you will see the upflow, for a moment, and then the fluid level should lower slightly as the pedal is moved towards the floor.
As to the air pack putting air into the system, I would be more inclined to believe that the airpack is allowing air to enter into the system on the return stroke. While it is possible that pressurized air can get into the master cylinder brake fluid, you have to remember the input pressure of the hydraulic fluid is about 550 psi and the air system is at 100 psi approximately. Logic says that the fluid would infiltrate the air and not the reverse. Then again, I am humbled every time I see a new twist that I had not anticipated.
Cranetruck (Bjorn) here on SS is a legend as far as I am concerned in his research and understanding of the brakes on a deuce. The factoids I use are derived from his writings.

Hope this helps;
RL
 

WOLFMAN1

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i had the cap off of the master and pushed the brake with the truck off. even though i hadn't bleed the system yet. the fluid in the master rised and then went down as i pushed the pedal farther down. is this a good sign. I know i should really bleed the brakes . im just short handed of help.:oops::deadhorse:
 

rlwm211

Active member
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Location
Guilford, NY
Your best bet is to bleed the system. If you have a helper, you start with a full master, and bleed the airpack. Once you have a steady flow of fluid;
you refill the master and then go to the rear of the truck and
bleed the Right rear;
Refill the master;
bleed the left rear;
refill the master;
Bleed the front left rear;
refill the master....you can see the process here.

Notice the emphasis on REFILLING THE MASTER....

The master cylinder holds a woefully small amount of fluid. I would estimate 4 full pumps of the pedal max. If you let the master go too low, you start this all over.

You can bleed the system alone. Instead of having an assistant known in miltary parlance as "SOLDIER B" you have a quart bottle, such as a gatoraid bottle, or some other broad bottomed bottle. You need an 18" hose rubber, that is a snug fit on the bleeder. 1/8 vacuum hose is what I use. Pour a small amount of brake fluid into the bottle. About an inch.
You loosen the bleeder and put the hose over the end of the bleeder and in the bottle so it is below the surface of the brake fluid in the bottle. Pump the pedal SLOWLY two or three times.
Return to the bleeder you are working on, and turn the hose to snug the bleeder. Once it is set, then tighten it with a wrench and go on to the next bleeder in your sequence.
Remember to refill the master after each bleeder you do. You will gather brake fluid in the bottle. If it is clean, you can reuse it. If you are not sure, do not reuse it.
It takes about a quart and a half to bleed a truck, and fill the system completely. This is my estimate and I may be way off.

Once you have bled all the wheel cylinders you should have some pedal. If you do, but the pedal is low you probably need to adjust the brake shoes which is in the next lesson when you ask your next question.

Hope this helps

RL
 
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WOLFMAN1

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the cds i have show me how to bleed the system with two people thanks for the info. it wont hurt to use a rubber hose? the reason that i ask is that i want to run a vent line into the cab of my truck. can i use a rubber hose to do that. i plan on adding a resivor for fluid later on but for the moment wil a rubber hose on a brass fitting in the filler cap work to let the air out? :deadhorse: darn old truck
 

rlwm211

Active member
1,648
18
38
Location
Guilford, NY
The rubber hose is used only if you are bleeding your brakes alone. You need to keep the bleeder from pulling air back in when you release the pedal and let it up. It actually is a neater job to use some sort of container to collect the fluid that comes out when you bleed the brakes and makes spotting the leaking wheel cyllinder easier.
I am pretty sure there are some DOT approved nylon or some sort of composite plastic type tubing that will work nicely for a remote brake resevoir setup.
 
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