1971 Am M109A3

1971 Am M109A3 Brakes Please Help!

Hello,

I'm new here, I've been enjoying my M109A3 for a while.

It's been sitting a while (few months) with normal startups etc, but the other day I noticed my brakes had no feeling, moved it a bit and no brakes at all.

I've never worked on or even checked the brakes, so i go searching them down, hell now i can't even figure out where the heck to put brake fluid in at?!

So my question is, 1: Where do you add brake fluid at? Check Fluid at?

2: I drove this thing for about 500 miles now without one issue. I let it sit few months and the brakes don't have any feel to them. Any ideas?

Thanks a ton guys!

Read the TMs and Operators Manual...master cylinder is under the small door in the floor.

Bill

Yes Sir I found that, but i don't see what to do, take off or unplug to add or check fluid. I'm looking in the TMs lol there is a lot of them.


Thanks

rockman said:

Read the TMs and Operators Manual...master cylinder is under the small door in the floor.

Bill

Click to expand...

It shows in the manual that it has two caps, but mine does NOT have that. It looks solid with one line coming out of the top of it and no where does it look like you can take a cap off and add fluid. It looks like i could undo the line at top and add some there, but it does not look like that's how I should do it.

rockman said:

Read the TMs and Operators Manual...master cylinder is under the small door in the floor.

Bill

Click to expand...

The 2 TMs you need to study for starters is the operators manual TM 9-2320-361-10 and the unit maintenance manual TM 9-2320-361-20. Don't concern yourself with the other 200 or so manuals for right now. To be blunt, this truck should not have ever moved an inch without a brake fluid check. For safetys sake you need to studt at least the -10 manual. In case you decide not to study these vital manuals, you still need to know where the brake fluid goes. That little line is actually attached to the cap. It has a 4 sided 3/4 fill cap. A short 3/4 open wrench or a crowsfoot will help you get the lid off once the vent line is discoed. PLEASE, PLEASE read these manuals. Your deuce has a single circuit brake system which means one leak and you have zero brakes. See pic for an example of a cap.

Thanks a ton! Yes, I completely agree. When i bought it, the owner told me it was air brakes. I started looking around after no brakes and said "What the hell" lol Yea so that's where i'm at now. I'm very mechanical inclined and have about 80 percent truck figured out. Stupid me just thought it's air brakes... and just took his word for it. That part is my fault for sure.

Anyways thanks for the info...

Recovry4x4 said:

The 2 TMs you need to study for starters is the operators manual TM 9-2320-361-10 and the unit maintenance manual TM 0-2320-361-20. Don't concern yourself with the other 200 or so manuals for right now. To be blunt, this truck should not have ever moved an inch without a brake fluid check. For safetys sake you need to studt at least the -10 manual. In case you decide not to study these vital manuals, you still need to know where the brake fluid goes. That little line is actually attached to the cap. It has a 4 sided 3/4 fill cap. A short 3/4 open wrench or a crowsfoot will help you get the lid off once the vent line is discoed. PLEASE, PLEASE read these manuals. Your deuce has a single circuit brake system which means one leak and you have zero brakes.

Click to expand...

How fitting that you post this on Thanksgiving! Truly, you should give thanks that you, your family, and other motorists have been enjoying your vehicle without injury thusfar.

Unlike all passenger cars produced in this country over the past several decades, your truck has a single circuit brake system. This means that any leak or failure results in the no brakes whatsoever condition that you have now found - and there is no warning whatsoever.

Yes, the master cylinder is beneath the door in the driver's floorboard, and then beneath a piece of hat channel that reinforces the floor. To check the fluid (which likely is low), disconnect the small copper line attached to the elbow in the top of the master cylinder. Then remove the large plug in the top of the master cylinder. However, merely topping off the mastercylinder is rather like putting a band-aid on a stab wound - it only slows the problem.

You should set out to find out where the brake fluid went. That means check the six wheel cylinders as well as the air-hydraulic cylinder (another item not found on passenger cars), as well as the lines. While evidently thusfar you have had only slow leak, it at any time could become a major leak - an aged, swollen rubber brake line, for example, can rupture at any time. In such circumstances you instantly have NO BRAKES whatsoever. This is not like your car, where you have "a few more stops" - but rather you have no more stops.

Give thanks today that this problem happened in your driveway, tomorrow read the manuals, and Saturday break out the wrenches!

Best wishes,
David Doyle

Neosin said:

Hello,

I'm new here, I've been enjoying my M109A3 for a while.

It's been sitting a while (few months) with normal startups etc, but the other day I noticed my brakes had no feeling, moved it a bit and no brakes at all.

I've never worked on or even checked the brakes, so i go searching them down, hell now i can't even figure out where the heck to put brake fluid in at?!

So my question is, 1: Where do you add brake fluid at? Check Fluid at?

2: I drove this thing for about 500 miles now without one issue. I let it sit few months and the brakes don't have any feel to them. Any ideas?

Thanks a ton guys!

Click to expand...

Just a small correction in case someone else search for this.

Correction :
operators manual TM 9-2320-361-10
unit maintenance manual TM 9-2320-361-20. not "TM 0-"

Recovry4x4 said:

The 2 TMs you need to study for starters is the operators manual TM 9-2320-361-10 and the unit maintenance manual TM 0-2320-361-20. Don't concern yourself with the other 200 or so manuals for right now. To be blunt, this truck should not have ever moved an inch without a brake fluid check. For safetys sake you need to studt at least the -10 manual. In case you decide not to study these vital manuals, you still need to know where the brake fluid goes. That little line is actually attached to the cap. It has a 4 sided 3/4 fill cap. A short 3/4 open wrench or a crowsfoot will help you get the lid off once the vent line is discoed. PLEASE, PLEASE read these manuals. Your deuce has a single circuit brake system which means one leak and you have zero brakes. See pic for an example of a cap.

Click to expand...

Fixed my typo!

Isn't it funny. Granted as scared as you might be of it, you can stop with out normal brakes, in fact practice it! I'm surprised from the sounds of it no one chimed in telling me to use engine breaking with engine killing to stop "should" brakes go out. That's a standard rule should an event like this happen. Also, i would think the parking brake is manual on this thus giving one more line of braking? If not, it'll be changed soon lol I'll read up.

However, even know there is a rule to stopping. LOL stopping without breaks... NO FUN!

Thanks guys for the info. Now knowing what I do, i plan to put eyes and hands on every brake item there is on this truck.

DDoyle said:

How fitting that you post this on Thanksgiving! Truly, you should give thanks that you, your family, and other motorists have been enjoying your vehicle without injury thusfar.

Unlike all passenger cars produced in this country over the past several decades, your truck has a single circuit brake system. This means that any leak or failure results in the no brakes whatsoever condition that you have now found - and there is no warning whatsoever.

Yes, the master cylinder is beneath the door in the driver's floorboard, and then beneath a piece of hat channel that reinforces the floor. To check the fluid (which likely is low), disconnect the small copper line attached to the elbow in the top of the master cylinder. Then remove the large plug in the top of the master cylinder. However, merely topping off the mastercylinder is rather like putting a band-aid on a stab wound - it only slows the problem.

You should set out to find out where the brake fluid went. That means check the six wheel cylinders as well as the air-hydraulic cylinder (another item not found on passenger cars), as well as the lines. While evidently thusfar you have had only slow leak, it at any time could become a major leak - an aged, swollen rubber brake line, for example, can rupture at any time. In such circumstances you instantly have NO BRAKES whatsoever. This is not like your car, where you have "a few more stops" - but rather you have no more stops.

Give thanks today that this problem happened in your driveway, tomorrow read the manuals, and Saturday break out the wrenches!

Best wishes,
David Doyle

Click to expand...

Gotta say thanks again. I really was not thinking anyone would reply so quickly... Maybe I'll stick around a little more.

Having been one of those that have been without brakes twice now, once is a 20,000# deuce and the other a 12,560# deuce towing a 13,500# deuce, I can say from experience you ain't gonna stop it with compression braking. Your only hope is to get it to second gear (lowest with a synchro) and slip the clutch against a non running engine. Been there done that, still have canvas marks on my backside. I can also say for certain that the parking brake is just that, parking brake. Any hopes of it scrubbing off a few miles per hour are pipedreams. It holds great once the truck is stopped but once rolling, you can plan on rolling a mile before it stops you. On one of my experiences, I was only able to get it into 3rd gear and it had no problem running the non running engine up to 3000RPM with only negligible compression braking. This is not Monday night quarterbacking, these are real world experiences.

Neosin said:

Isn't it funny. Granted as scared as you might be of it, you can stop with out normal brakes, in fact practice it! I'm surprised from the sounds of it no one chimed in telling me to use engine breaking with engine killing to stop "should" brakes go out. That's a standard rule should an event like this happen. Also, i would think the parking brake is manual on this thus giving one more line of braking? If not, it'll be changed soon lol I'll read up.

However, even know there is a rule to stopping. LOL stopping without breaks... NO FUN!

Thanks guys for the info. Now knowing what I do, i plan to put eyes and hands on every brake item there is on this truck.

Click to expand...

Having driven a few thousand miles in these trucks over the past many years, I'll give you a couple of tips regarding the use of the parking brake as an emergency brake. Indeed should the service brake system fail at low speed, yanking the parking brake on is a great first step, but I'd sure not bet my life, or anyone elses, on it. If at high speeds or a heavy load - likely all you'll do is toast the parking brake, or make it shed the lining.

You should be aware of a few of things.

First - by design its a PARKING brake - the design specs do not envision it being used to halt the vehicle. And its peformance reflects this.

Second - these are notorious among users for being marginal, even for parking. Even the parking brake performance was noted as being marginal in the original 1949 Aberdeen Proving Ground test report.

Third - given the condiition of the service brake system, I'd say that on your vehicle there is a better than average chance you'll find a seal leak has allowed some oil saturation of the parking brake shoes. You should aware that this system is a sheet metal drum on the driveline with two shoes - NOT a cable actuation of the service brake shoes like most passenger cars.

The reason that no one chimed in as to engine braking is no one wants to get you killed. You should be aware that published data (available on this site in the PS magazine section) from the Army, who has more experience with these trucks than any of us, has proven that in many conditions attempting to use a Multifuel engine as a brake actually results in the vehicle accelerating. (unlike many gasoline engines, the Multifuel has no inherent vacuum, the only braking ability it has is the friction of its moving parts and their mass). On flat level ground, it will tend to slow the vehicle, under other conditions the opposite is the case.

I am not "scared" of any of the dozen or so 6x6s I own, but I do respect them, their limits, and mine.

Best wishes,
David Doyle

I kind of figured I'd run into a few like you guys on a site like this.

compression braking has nothing to do with vacuum. LOL it's using the compression of the engine, you know when you quit adding fuel it's still making compression on all 6. Hills sure your out of luck, 15,000 - 20,000 LBS and your going right down a hill. LOL the compression won't do anything, and no it's not going to "speed it up"... how in the hell does adding more friction and compression without fuel going to "speed" up. Come on guys pulling one's leg and sounding like a jerk at the same time... well that's just funny to me.

Now, let's see your jumping my case here, I had brakes go out in my backyard. Doing 1/2 mile an hour. You said you had brakes go out say what? TWICE? ON ROAD? Who's not looking at things? LOL It seems to me if your having your brakes go out then you might wanna start looking into who's working on the machine. On road i've never lost brakes. However with loads and what not in my excursion engine braking works great. Don't know if you have ever been to Houston, but we don't have anything that even remotely looks like a hill. On our flat ground engine braking has worked quite well in my M109A3. Maybe you guys should have your engines looked at? Because mine will engine brake very well. However that's with no load in the truck just it's 15,000 lbs. But my engine is rebuild with 1000 miles on it. Once i get the brakes working, I'll record a video for you to show engine braking works just fine. No it does not stop you on a dime...


Now i will say you guys are right on the parking brake. It's a joke. You could make it work right but it's not going to stop the truck like normal brakes, your right about that.


Recovry4x4, thanks for the info. Thanks for pointing me to the pages so i can get started fixing this thing. David Doyle here seems to be on a one track mind of "setting" me straight.

Considered me straight buddy. I already have one daddy figure in my life... Let's try and fix issues and help others that run into the same issues clear up these kind of problems.Sorry if i struck a nerve.


nuff' said.





Now here's what I'm trying to do. Fix the dang brakes correctly. However I'm not gonna run all over the place, I'd like to take it step by step.

Currently
Brakes worked 100% just a few months ago. Checked them the other day and no brakes.

Today - The MC was bone dry. Nothing I can see around the MC looks wet with fluid. I had the top off with the truck running and pumped the brakes and i could see a little fluid movement every now and then. With it all buttoned up still no brakes, checked the MC again no fluid loss. Air pressure is just fine without any leaks.


Tomorrow, I'll get under it and look for more leaks. I'll check the MC after overnight sitting... Can you guys give me the order of which to check for leaks? MC, lines, etc? I know you guys know this far better than I and figured if your all gonna be my daddy well let's get to it. FYI there is no feeling in the peddle. To the floor and it will spring back up.


Take care guys.

Brian

I work on my trucks and yes, I've blown brake lines so I know what the story is. If you drive enough miles, you too will have a failure, guarantee it. I've got many many thousands of miles on them. For you to come in here and throw stones at my mechanic ability saying who's not looking at things is kinda premature from a guy who also drives a deuce but doesn't know where to add brake fluid and can't find the cap. At least my brake failures were because of a part failure not running it out of fluid. 2 of your very best sources of info are trying to give you advice and your biting back at them? Now for a little education on compression braking. There is nothing in a diesel to restrict the flow of air through it like a gas motor. An engine is just an air pump and if there is no restriction, the motor will just keep turning as the vehicle pushes it. I'm not speaking of some book terms, my experience is from the drivers seat.

NEVER trust the parking brake for ANY emergency stopping. Exccesive torque against the parking brake (like say just letting the clutch out in reverse/low with the brake on) can snap the cable. I have done it!

As to a 'couple guys like this'... Brian, you are talking to 2 of the MOST respected guys when it comes to deuces. I would suggest you not argue with them, and learn from them.

Possible lose of brakes in a 13k pound truck is nothing to write home about. You came in here, asking how to fill the brake fluid... AFTER you had driven the truck. That tells me you couldnt even be bothered to read the manuals first?


BTW... compression braking in a deuce is a joke... It may aid in slowing for a few seconds... but thats about it.

He'll not learn more from me - he is in Houston, Texas - I don't drive there so he won't run over me or my family.

BUT, for a man who'd never checked the brake fluid, and doesn't know how to, in a 20000 lb truck to come on here and start talking trash just proves what kind of idiot he is.

He does not respect his fellow motorists, his passengers or his family. I say the later because when his lack of basic understandings as to how the truck works, or how to maintain it causes an injury, the resulting judgement could cost he and his family their home. And that is how it should be, before he costs someone their life.

I've scanned and posted the Army document (from PS magazine issue 344, July 1981 - an official U.S. Army publication) regarding engine braking in these vehicles - or lack thereof - not for this over-confident bozo but for future visitors who actually want to learn something.

Of course Brian (aka: "He who can't check the brake fluid") knows more about this engine design than the army whose been using it for 40 years - so maybe you should contact the Department of Defense and "explain it" to them like you have to Kenny and I. Tell them that their research and published articles are all wrong and that they are "pulling one's pulling one's leg and sounding like a jerk at the same time" - that engine braking works fine cause you say so.

By the way between us Kenny and I likely have 20 of these trucks and have driven them several times as many miles than you have in yours. You wanted answers from folks with experience, and you got them - politely. You thanked us with an attitude. My "one track mind" was that you, your family and your fellow motorists live to see many more Thanksgivings. Your one track mind seems to be "I don't no ____ from shinola about these trucks, but I know more than you guys" - but so far you've certainly not proven that.

Yes, there are few of "us" on the site - actually a LOT of us - those people who actually can and do read the manuals, those of us who actually care about our fellow motorists, and those of us who try to help people who ask questions. And there is at least one of us who does this professionally. Fortunately there are not many of "you" on the site - folks who ask questions, get the facts, don't like them, so show their rear.

Regards,
David Doyle

To quote NEOSIN
"I kind of figured I'd run into a few like you guys on a site like this. "
Are you referring to knowledgable, helpful, polite people with way more experience with these vehicles than you. People who have taken them completely apart and put them back together. People who have read all the manuals cover to cover. People who have written tech articles for national publications. People who have written books on these vehicles.
People that are here without an "attitude" other than to help others NOT cause harm to themselves and others through ignorance and poor operation and lack of proper PM on these vehicles.
If these are the kinds of people you are talking about, you will find that there are a lot more than a "few on a site like this". This site is full of people like that.
BC

Here are a couple of other things you might want to consider.
I found this info on Mark's Green Truck pages
http://www.nf6x.net/greentruck/m44xref/m44xref.html

Unless your truck came right out of military service, make sure that the previous owner did not top up or replace the brake fluid with ordinary DOT 3 or DOT 4 fluid before you add any DOT 5. BFS Brake fluid, silicone, automotive, all weather, operational and preservative MIL-B-46176 DOT 5

http://speedbleeder.com/
According to Mark, These replacement brake bleed valves make brake bleeding a one-person job. Part number SB71620 fits 2.5-ton multifuel trucks.
===================================================
Personally I think I would flush and refill the brake system with fresh fluid.
Regards Rick

For fixing your brake problems, I'd recommend checking all 6 wheels for fluid leaks, and maybe even bleeding the brakes to see if you've got air in your system (even though you would have a slight bit of braking power in that situation).

You may have a blown wheel cylinder or something, seeing as you have absolutely no brakes.