Need help with brakes M35A2 in Austin, TX

[DrFuzzy]

I seem to have a leak somewhere in my brake system, or a failure in the air cylinder.

I have already replaced the brake fluid as per the TM (used approximately 110 oz of DOT5 to get all the air bubbles out of the air cylinder and all 6 brake lines), but I sill have no braking action and the pedal just goes to the floor.

The air compressor pumps up and registers 60+ psi after about 60 seconds, and the warning buzzer goes off after 2 or 3 minutes. So it's not an air leak.

Any deuce mechanics willing to make a house call for $$$ in the Liberty Hill area?

PM for my phone number.

--Fuzzy

 

[hndrsonj]

Was the system bone dry or was there fluid in the system? Did it work before? Did you use a pressure bleeder or do it the old fashioned way? There aren't any visible leaks right (aren't losing fluid)? I couldn't get mine to bleed right without the power bleeder.

 

[wb1895]

You may have a bad master cylinder. Mine was bad when I got my deuce, I just ordered a new one from Saturn Surplus.

 

[DrFuzzy]

I did it the old fashioned way (no power bleeder). My wife played the part of soldier #2.

It worked just fine for several months when I first got it. Came back from vacation and it was bone dry (it sat unused for 1 month).

My mechanical expertise is robots, not vehicles, so this is my first brake system to diagnose and repair. That's why I'm looking for help.

Aside from finding a leak (now that I have all new fluid in it, I can look for purple spots on the ground), how can I tell if my master cylinder is bad?

--Fuzzy

 

[hndrsonj]

Check the inside of each wheel for a leaking wheel cylinder-leak should be obvious. If there aren't any and no leak at the master cylinder it is probably leaking internally from the airpack. You will probably find the leak though. You bled it at the air-pack first right?

 

[Tinwoodsman]

Might want to call Lynn at Militarytrucks.com in Liberty Hill.

 

[DrFuzzy]

Yep, bled the airpack first...seemed to take forever to get rid of the air bubbles. Put in about 70-75 oz of fluid and almost all of it came out the bleeding hose with bubbles in it (at least 60 oz in the jug).

I'd have expected that a major leak would have presented itself during the bleeding process, but none was apparent.

--Fuzzy

 

[DrFuzzy]

Already called Lynn...he can look at it if I get it working, but otherwise I have to flat bed it out to him.

I was hoping to find someone to come out to the ranch and look at it. Not looking for a freebie, just need to find someone who knows how to work on a Deuce.

--Fuzzy

 

[hndrsonj]

Well you need to figure out where the fluid is going first. If it's not a wheel cyl or the Master cylinder, my gut says air pack. I believe if it's leaking internally you can pull the NPT fitting out and confirm the bypass. I have never had that problem though, hopefully someone who has can chime in here. I'd definately get the power bleeder though. It will pay for itself the first time used. Mine was the best $45 I have spent yet.

 

[Heavysteven]

Power bleader is worth every dollar.

 

[rlwm211]

I would suspect your master cylinder. That is why you kept getting bubbles. The seals are failing and the rear seal of the master holds the fluid for the next time the master need more fluid. It also can admit air especially if it is bad.

I would pull the rubber boot off of the master piston rod where it slips over the master cylinder flange and look for fluid. If you find fluid, the master needs to be rebuilt or replaced. Without a good master you cannot properly bleed your brakes without a pressure bleeder.

I suppose I should have asked if when you bled the air pack bleeder, which is the first place you bleed, you should have gotten a solid strong stream of fluid. If you did not, then you have additional evidence that the master is bad.

Losing fluid is a cause for concern and a whole master cylinder of fluid might not always show up on the inner portion of the tires. I had a weeping wheel cylinder and it took filling the master twice to see the fluid on the tire.

I would offer that the booster has nothing to do with bleeding the brakes so it probably is not the problem at this point. The military designed these trucks so the operator has marginal braking for very slow speed operation if the air system fails. Even with the booster not functioning, you should get a firm pedal.

If you inspect the master and find fluid in the boot, you have ended your hunt.

Hope this helps

RL

 

[hndrsonj]

He said he has no visible fluid leakage. The quantity of fluid in the M/C will not fit in the boot, so where is the excess fluid? Also the airpack is what gives the boost but it can leak internally hiding the fluid. He says it's bled right and no visible leaks.....

 

[clinto]

1. do the power bleeder. WELL worth it.

2. When I am not sure where a vehicle is losing brake pressure, I first bleed the system (at the airpack and 6 wheel cylinders). Still no pedal? I remove the output brake line coming out of the master cylinder and plug it. If you have pedal pressure at that point, you know it's the airpack. Still no pressure? You have a bad master cylinder.

C

 

[hndrsonj]

That's another great reason to get the bleeder, you can put pressure in the system and see where it is leaking.

 

[rlwm211]

Clinto, good point on evaluating the master. That would simplfy things immeasureably.

I have rebuilt several of the deuce air packs and I would find it very extraordinary for the air pack to leak internalyl in such a way to absorb 10-14 ounces of fluid the master holds. I will not argue that it could happen however.

If the master is leaking into the boot, and the boot is leaking it can drip to the ground especially if the master is not dumping brake fluid, but merely dripping.

The lack of pedal can be internal to the master cylinder so it can have no brakes and not be leaking appreciaably. The primary seal on the piston can be torn, or worn to a point where it fails to pressurize the brakes and simply bypasses the fluid under pressure..

I would suggest we also remember that we have no definitive time or how long it took for the fluid tp disappear. We only know that it was discovered to be gone after the truck had been sitting. I would wager a slow leak resulted in the loss of fluid and may not leave a distinct indication of a leak in the short term. I suspect that it is the master because of the lack of pedal. I could be wrong and will admit so right now to make sure no one suggests I am excluding that possibility.

I have done brake bleeding alone, without a pressure bleeder. It is quite simple and I used the old fashioned method of using a container with brake fluid in it, with a hose from the bleeder with the end under the surface of the brake fluid. The deuce master pumps about 4-5 ounces (perhaps a little more) per full stroke. I found that after two full cycles of the pedal, I refilled the master. As a result, my truck has good brakes and they have held up all year. I would add that there are probably many ways to bleed the brakes with or without help.

I hope our discussion of the merits of one suggestion over another have not disctracted from our intentions of trying to offer some education and advice to solve your problem. If I lived closer I would certainly be there to try to help you out. Unfortunately I do not generally make house calls to Texas from the Southern Tier of New York State.

RL

 

[hndrsonj]

Another way to think about it is, air pack rebuild kits are cheap on ebay. I'd just rebuild both the M/C and airpack. That way you know the system is correct. I'd even do wheel cylinder kits (they are $5-6 ea).

 

[ericm38]

I had the same thing happen my problem was the airpack. It would put air in the system. When it started was when I hooked up my trailer air line. Then it was down hill fought with air and lost a quart of dot 5 from bleeding. Take the top off the master and hit the breaks but cover with a rag my 2 cents good luck

 

[Barrman]

Check your airpack vent line. If it is full wet and just dripping fluid, then the airpack is blowing the fluid out the vent and needs a rebuild.

Can you pump up the brake pedal to get pressure? Do you hear the pssst of released air after you let go of the pedal?

I am only 80 miles away, but it might as well be 500 with my schedule. Sorry I can't come over to help. Do you have the new short style air pack or the old long style with the removable end?

 

[DrFuzzy]

I'll crawl back under the beast and look for leaks, and check the air lines.

Pumping up the brakes does NOT increase the pressure, and I hear no air noises on either a down-stroke or an up-stroke of the brakes.

The frame is a 1964, but I believe the truck is a chimera of at least two different vintages (the dash says it's a 1973).

I'd actually like to have the whole brake system rebuilt; I'd feel safer driving it. My nightmare is a 4th of July parade in a park full of kids and the brakes stop working. I just don't have the experience and knowledge to trust myself to repair or rebuild an air-over-hydraulic brake system.

I *do* have a 20K gooseneck flatbed, so my next plan is to put a winch on the gooseneck, pull the the Deuce up onto tjhe flat bed, and then take it somewhere to be fixed.

--Fuzzy

 

[shootiniron]

Where can I get a power bleeder?