Master Cylinder help

[TommyG45]

Hey all,

I am wondering if someone can help me out with a little info. I was going through the brakes on the deuce and checking out the master cylinder. When I unbolted the access panel and looked in the hole, I noticed a brake line hanging in the breeze. After reading the TM, I think it is a vent line. It is regular brake line with a fitting on the end. Being new to the deuce, I have no past experience to draw from. Having only one deuce, I have nothing to compare it against.

So, what I expected to see.... I expected to see a reservoir with a cap that you would pop off and fill above the min and under the max lines.

What I have is what looks like the adapter as identified in the TM, with a 90 degree elbow connected to nothing. It looks as though if I got something in there to tighten it another ¼ turn, the line flapping in the breeze would line up with the elbow connected to the adapter, and I could make the connection.

The 90 degree elbow, is that the filler cap?


The TM says to fill ½ inch from the top. Also, hanging down from the wire harness is a two prong female plug ( I think is was two prongs) No sure where that goes, I do know that the brake lights don’t work. Is there a connection to the airpack or the master cylinder that I missed. (switch settings on dash are correct)

The TM I got from my search really didn’t get me the level of detail I needed with my experience level to solve the mystery. If I need to order parts, it would be helpful to get a very detailed breakout.

The TM I used is on my work PC so sorry I couldn’t tell you the exact number.

It could be that what you see is what you get.

Can anyone confirm for me what should be coming out the top of the master cylinder when looking at it through the access panel? Any suggestions on the electrical connector would be helpful also, just seems too convenient that the brake lights don’t work, and the proximity to the MC and Airpack.

Thanks all

Tommy

Update, Thanks to a post on brakelights just a few down from here, I have several things to check concerning the lights.

 

[Boatcarpenter]

It seems to me that you have it figured correctly. Loose line is probably the vent. The two wire or two prong connector does probably go to the brake light switch on the front of the MC. Should be a rubber boot, watertight connection. If I didn't have to walk out the door to go to a meeting I would find a diagram for you.
BC

 

[emmado22]

(Serious mode on)
Holy cow, a guy that actually did a search, looked at the TM, and asked an intelligent question. If I had the answer for you, I'd answer you. I wish more posters would be like you.

And I am being totally serious..... After the rash of ongoing "if you look in the TM, you'll find the answer you need" type of questions, this is a refreshing change....

As for the brake lights not working, sounds like your switch may be bad. If it's an old hydraulic type valve, it's a good time to change to a new style air operated one. Many posts cover that.

Let us know if you need more help.

 

[doghead]

The master cylinder cap has a square "head" on it(3/4" iirc). It is what the elbow you see, is screwed in to.The vent line does need to be disconnected to fill the master cylinder. It sounds like your vent line was left off (for unknown reason) and your brake light switch is unpluged. The Brake light switch is at the lowest and most forward part of the air-pack. Some times, I have seen them unplugged because the switch has stuck on, check yours before reconnecting it. Use an ohm meter and it should be open with no brakes and closed with brakes applied.

link with a nice picture of a master cylinder and associated parts. the cap is shown with the vent line attached in it. http://www.steelsoldiers.com/index....ewtopic&t=15824&highlight=master+cylinder+cap

 

[doghead]

here's a link showing both the original and the upgraded brake light switches. http://www.steelsoldiers.com/index....ht_switch&name=gallery&include=view_photo.php

click on the left page to make it bigger.

this picture is a hydraulic brake fluid switch

 

[doghead]

Oh, one more thought! You are aware that the brake fluid is most likely Dot 5 BFS(brake fluid silicone), right? Let us know how it's going.

 

[TommyG45]

Guys,

I can’t thank you all enough for the information. I am amazed at the info you guys can pull up. As I get better with the search engine, and the terminology, I think I can narrow down the posts a tad bit better. The content on this forum and the very people who lend their experience so freely is what drew me into the world of green to begin with.

Incase you don’t hear it as often as you all should, thank you very very much. You guys are very appreciated !

I will keep you up to date on the progress, I have Thursday and Friday off, and have a date with the deuce.

 

[TommyG45]

Doghead,

When I was reading through the posts, it looked like there were two choices, DOT3 and DOT5 and then some commentary on not to mix the two. I was going to go with DOT5, am I rolling the dice and taking too big of a chance. Whats the odds there is DOT3 in there. Any way to tell?

Tommy

 

[WillWagner]

I flushed mine and used DOT5 off the shelf. No issues as of yet, three years of service.

 

[doghead]

Sure, take some fluid out of your master cylinder. Put it in a paper or plastic cup. Put some(about a tablespoon) water in with it and stir it up some. Let it settle for about a minute. See if the two stay mixed or separate. If they separate, you had dot 5, if they stay mixed, you had dot 3. If you have any doubts, do the same with new dot 5 and water and do it with some dot 3 and water.Then make a comparison, does that make sense? If your truck was fresh out of the military, it's pretty safe to say it has dot 5.

 

[TommyG45]

Makes perfect sense, the deuce was retired from the Indiana NG in early 2008.

 

[emmado22]

I'll put my $$ on it's DOT 5 in there.. The US Army stopped using DOT 3 a LONG LONG time ago.... It's the only brake fluid in the Suppy System...

They call it BFS (Brake Fluid Silicone). it's purple when its in the bottle, but turns yellow after a while in the brake system.

 

[TommyG45]

Hey guys,

Here is what I experienced. The vent line is now reconnected after topping off the master cylinder. There was still plenty of fluid in the system, but filled it to the recommended 1/2 inch from the top just the same. With the vent now connected, and fluid level at spec, there was no difference in the brake. Not a problem as the brake was fine to begin with, not sure how the venting system is supposed to work. Observation, not made to be serviced by and individual over the age of six. Tight space, not a lot of room to work in there.

I was concerned when I had seen the vent line disconnected, it's hooked up now.

The brake lights not working, was the switch disconnected from the harness on the airpac. I was thinking that was way too easy and waited for a full 60 seconds to be struck by something falling from the sky. That was a simle fix.

Transfer case took two quarts of 90GL-1, transmission took just a quik squirt using the single knuclke rule.

The diffs were full, but will eventually need to be changed, when I have some more time, I am going to go through the entire deuce and purge everything.

While I was at it, I did the Napa muffler Mod, what a difference that made. I will still wear hearing protection as it still gets pretty loud in the cab at around 50MPH.

I drained the air tanks, inspected the glad hands, and replaced the rubber seal on the emergency glad hand. I did a test jack up on the rear diff to test out the 20 ton air/hyd jacking system and verified operation of the air impact wrench.

Topped off the engine oil, looked very clean, so someone changed it prior to taking delivery. Did not require oil. Got two gallons of RT 15W-40

I haven't chcked the air cleaner yet, but the indicator reads ok in the cab.

Making progress, little at a time.

Thanks again guys for all the help.

Tommy

 

[ida34]

The vent line just moves the intake for the vent higher up on the firewall. This is for fording. My five ton has an axle vent on it in stead of the vent line. The axle vent lets pressure out but closes shut when it senses pressure from the outside as when water tries to enter the housing. The vents are used on the axles, transmission and transfer case. Leaving the vent line off would not hurt much until you tried to go through water higher than the master cylinder. As a note, Never cap off the hole for the vent. Air must move in and out for the master cylinder to work properly.