Brake Pedal Goes to floor suddenly out of the blue

[redjordan]

So I went out to move the deuce last nite, and the brake pedal goes almost to the floor, with a tiny bit of grab at the last inch of travel. Looked around in the dark, and it really does not appear to be leaking anywhere, my first thought was wheel cylinder.

Anything else common that would cause this? Ruined my night

 

[rlwm211]

Check the fluid in the master. That is likely the cause. You have to understand that the master cylinder of a deuce holds a pitifully small amount of fluid and if you have a leak, it may not show up on a tire or rim until you are literally out of fluid, or even after, if you refill the master a couple of times. Ask me how I know this?????

If the master is full you have to determine if the master is working at all. Generally if it worked yesterday, it should work today unless you had a panic stop or some other event to cause a seal failure. The air pack can fail, but even so, it should still provide a firm pedal.

My bet is you are out of brake fluid....post what you find and we will go from there.

Hope this helps
RL

 

[Paul Wolfe]

Hi,
If the fluid level is OK, it is most likely the master cylinder. I once had a car do this. You may find the next try you will have brakes.

 

[USAFSS-ColdWarrior]

FYI.... ALWAYS fix any Deuce Brake Problem BEFORE trying to ram your foot/leg through the floorboards for a "FRED FLINTSTONE" style stop..... You will find you're legs are just TOOOOO short to reach the ground.

 

[Troll1216]

IF you have fluid be sure to bleed the brakes with a power bleeder and check for bubbles. IF there are no bubbles, then it will most likely be a bad master.

Your description of the problem is exactly what mine did... Order a new master and rebuild the old one. Mine was $85, prpbably overpaid, but I got a 2006 contract part. I think rebuild kits are $35.

DON'T DRIVE IT!!! They are NOT FUN to stop even on level ground with no brakes and the parking brake is just that, a PARKING brake.

 

[Heavysteven]

Since you have no brakes now. I suggest going through the entire brake system and rebuild/replace any questionable parts. It's expensive but you need to know that when you hit the pedal your truck will stop.

I have a rear brake hose that looks ify and its going to be replaced today. Also, I got my power bleeder to make life easier.

 

[JCKnife]

Okay, I've been looking at my brake system lately and I have a very remedial question that I was hesitant to post but here goes: how do you open the master cylinder?

I have searched the -10 and -20 manuals and this site and can't find the answer to that.

Attached is a pic of mine. What is the little silver cap? It spins freely but does not come off by turning.

 

[Carl_in_NH]

See how the plug in the middle has a raised square shoulder? Put a wrench on it and unscrew it.

The little silver cap is a vent.

EDIT: Make sure you clean it well before unscrewing the cap so the crud doesn't drop down into the fluid.

 

[Heavysteven]

Okay, I've been looking at my brake system lately and I have a very remedial question that I was hesitant to post but here goes: how do you open the master cylinder?

I have searched the -10 and -20 manuals and this site and can't find the answer to that.

Attached is a pic of mine. What is the little silver cap? It spins freely but does not come off by turning.

That's a spring vent normally there is a vent line running into the mc. You need a 3/4" wrench to unscrew the mc cap. There is a raised 3/4" square just below the spring vent. Make sure and clean around the area so no dirt gets in there.

 

[319]

That's a spring vent normally there is a vent line running into the mc. You need a 3/4" wrench to unscrew the mc cap. There is a raised 3/4" square just below the spring vent. Make sure and clean around the area so no dirt gets in there.

Get a stainless steel or brass brush (toothbrush style) and clean the cap and around the cap, then use compressed air to blow off the debris.

 

[JCKnife]

Ok that's really what I thought but wanted to make sure. Now I'll go read up again on determining which fluid you have so as to add the proper kind, if needed.

 

[6x6guy]

It's a good thing it happended in your drive, and not comming off a highway to a stop sign
or light at a busy intersection- lots of people have been hurt and even killed when
those brakes go- main reason I give more than I should in space in front of me when driving- learning for other peoples mishaps.

 

[rlwm211]

What is that silver cap?

Attached is a pic of mine. What is the little silver cap? It spins freely but does not come off by turning.[/QUOTE]


The silver cap is a breather that is normally used on an axle or transmission. Typically a deuce will have a copper line (1/8") extending from the master cylinder cap to the vent line of the air pack and then to the air filter assembly.

Someone has replaced this on your truck with a vent. Make sure it is free and moves up and down as well as splins. There is a tiny float valve that would seal the vent if you were to submerge it.

RL

 

[Heavysteven]

Well, crap replacing those rear brakes hoses and broke the T connection from the frame. Was in a hurry because I wanted to try out my new power bleeder.

Add me to the no brakes club...lol

Joe, I would reccomend a gallon of silicon from eastern supply. Very nice vendor.

 

[redjordan]

So I finally got to take a look today, still looks like zero leaking from anywhere that I can see. The master was about 85% full. I pumped it a few times while the cap was open and pedal got harder and harder, and now has brakes again more or less. Obviously I do not trust this, but any thought on what would cause this?

My vent on the top of the master does not go anywhere, its just a little cap thats on there.

Could the air pack have caused something? I guess I should try bleeding, some random air is the only thing I can think of since its not leaking or disappearing fluid. Anything else I should try?

 

[Heavysteven]

I would lube the airpack and flush the system. You really need to pull the wheels off and check all the cylinders.

 

[DieselBob]

So I finally got to take a look today, still looks like zero leaking from anywhere that I can see. The master was about 85% full. I pumped it a few times while the cap was open and pedal got harder and harder, and now has brakes again more or less.

Somebody please correct me if I am wrong but I don't understand how these vent caps are acceptable to use on the master cylinder. It is my understanding that they have a small disk that is held closed on the seat by a small, low tension spring. As the gear oil in the axle, transmission or transfer case, that they where designed for, heats and expands the pressure builds and moves the disk off the seat and relieves the pressure. Isn't this just backwards from the needs of the master cylinder. Lets say the the brake system has no leaks to deal with and just normal wear of the brake shoes is involved. As the shoes wear the wheel cylinder pistons will travel outward further and require more brake fluid to fill the space in the wheel cylinder. As more fluid is required by the wheel cylinders the level of the brake fluid in the master cylinder will decrease. If no allowance is made to fill the void left by the lower fluid level in the master cylinder a vacuum will form and brake fluid will cease recharging the master cylinder piston for the next application. So if we install a valve that is intended to relieve pressure, not vacuum, isn't this just setting up for a brake problem.

 

[Ord22]

i agree with heavysteven, check your cylinders.

 

[doghead]

DB, your correct. The axle vents do indeed cause problems, when used on the master cylinders.

A few threads have discussed this.

 

[DieselBob]

You really need to pull the wheels off and check all the cylinders.

In the middle of doing mine. Three wheels done, three to go. So far all three wheel cylinders look like this. They even have the cheap springs. So much for the USA made cylinders being better.