Brake Help

[mattg2448]

Ok, so i searched a little and didn't find any thing. What would be a good way to diagnose a brake system on a M35A2, I am trying to get my fathers truck on the road for Friday's Cruise Night and Im having a little issue.. The brakes are to the floor, opened the master cylinder and added fluid, put on the cap, pump it a couple times, same, to the floor. I'm assuming there may be a leak somewhere but where would be a good place to start?

 

[Heavysteven]

Check the brake hose, wheel cylinders, and bleed the brakes

 

[dozer1]

Matt, you will prob need to bleed the brakes like Heavysteven said. I would strongly recommend building a pressure bleeder like in this thread http://www.steelsoldiers.com/deuce/3229-deuce-power-bleeder-r4x4-style.html helps alot. Then bleed like the TM tells you . That bleeder will make it much easier.

 

[glcaines]

Make sure you are using DOT 5 brake fluid as that A2 most likely has DOT 5 in it and you cannot mix DOT 3 with DOT 5.

 

[mattg2448]

Ok, not trying to sound stupid, but I dont know spit about any thing.. Hahah! I am starting to understand all this brake stuff, but heres the question... When bleeding brakes, well.. how do ya do that? Hahahhaha Do i just crack the line at the brake backing plate? Crack it or take it off? I am building the pressure bleeder! So hopefully i can get er done by tomorrow!

 

[waayfast]

Ok, not trying to sound stupid, but I dont know spit about any thing.. Hahah! I am starting to understand all this brake stuff, but heres the question... When bleeding brakes, well.. how do ya do that? Hahahhaha Do i just crack the line at the brake backing plate? Crack it or take it off? I am building the pressure bleeder! So hopefully i can get er done by tomorrow!

Oh, yes you do know spit about something!! You know to ask for help on a very important (THE most important!)and complicated system on a 13,000 pound chunk of iron---the freakin' brakes!!!

Thank you for trying to help and thank you for learning this important job and not trying to bluff/guess your way into a train wreck.

I will let the more qualified people explain the procedure (I don't communicate well on the computer) but wanted to let you know you are doing the right thing!

 

[Welder Sam]

Very wise young man Matt.

 

[mattg2448]

Does any one find DOT5 expensive? 40$/Quart.. Thats RIDICULOUS!

 

[kennys@wi.rr.com]

Matt,

DOT is anything but cheap. I usually try to reclaim what I can with an empty DOT 5 bottle and a 3/8 OD hose on the bleeder. If it's got debry in it though don't even think of trying to reuse it.

When bleeding the brakes here is how I was taught to do it:
Start with the bleeder on the air pack.
Then move to the right rear wheel, then left rear...ect. You always start with the wheel furthest away from the air pack and move your way closer. Leave the bleeder open for a while. A few seconds and you have some fluid coming out means nothing. By using clear tubing off the bleeder you can actually see the small air bubble coming out of the bleeder. Wait until there are no more bubbles and it's done. Also don't fear when the new DOT 5 coming out of the bleeder is yellowish and the new fluid is purple. The color goes away after the fluid heats up, or so I'm told. If at first it is yellow and then comes out purple after having the bleeder open for a while, you know you have fresh fluid in the entire line.

If after doing all of this the brakes still do not work, then I would start to consider the air pack itself. When the air pack goes bad if it is still vented in a common vent line with the fuel tank and MC it will usually pump brake fluid out of the slobber tube. If you see that coming out of there now, don't even waste the time bleeding the brakes until you have rebuilt the air pack.

Hope this helps.

 

[Welder Sam]

Yup thatll take ur weeks grocery $$

 

[mattg2448]

Wooh hooo!!! It worked! Thank you kenny for the tips! It worked flawlessly! After bleeding, it had full brakes! Im very happy with this setup!

 

[Heavysteven]

Did you figure out what caused the brakes to lose fluid? Stop working?

 

[mattg2448]

Nope, but if it works in a couple days and dont loose pressure, i think we are golden, took it on the road and locked all tires up! Very nice brakes!

 

[Welder Sam]

Awesome job

 

[kennys@wi.rr.com]

Glad to hear it worked.

 

[Bob H]

21 hrs 3 minutes from
I don't have a clue to I built the bleeder and did the job successfully.

Out freakin standing gentlemen!

Excellent teachers and student.

 

[Bob H]

Oh and Brake Fluid - Silicone aka dot5

www.muskegonbrake.com

$15qt $40gal

 

[Mike929]

Wooh hooo!!! It worked! Thank you kenny for the tips! It worked flawlessly! After bleeding, it had full brakes! Im very happy with this setup!

To expand on this thread I picked up my truck today from GL. The brakes went to the floor when pumped as described above.

I checked the MC and the reservoir was empty, so I put almost an entire quart of Dot 5 in it and closed it up.

Pumped the brakes some and they got better and better until I got to the point that the first pump went almost to the floor, but the second would hold hard and stay. So I would release and wait a bit and sure enough the first one would go almost to the floor, but the second one was firm and would hold as long as I kept pressure on it. (no movement toward the floor and engaged all the brakes)

I have the USAF version with the dual circuit if that makes a difference. I assumed the problem was in the master cylinder and at minimum I have a leak in one of the connections, or the reservoir itself (i.e., the lose of the fluid in the first place.)

All wheel are dry and no sign of brake fluid. We did have some leaking at the MC, but I over filled a bit, so I don't know how much is my mistake and how much of it could have possibly come from a leak.

Any advice would be appreciated. (I will give a recover report tomorrow after I am better rested. It has been a long day getting the truck back to my brothers and it is there until I can bring the brakes to 100%)

 

[kennys@wi.rr.com]

The last truck I picked up, single circuit brakes, did about the same. I was able to determine it was the airpack by the fact it was spitting brake fluid from the slobber tube. That was an easy way to tell because of how the vents were set up at one time. With your truck I'm not sure how to tell for sure it's an air pack, but that would be a guess of mine.