never ending M135 brake problems!! Need advice??

[Brad]

Seems like I am back here every year at about this time.
I been trying so hard to get these brakes right on my late Fathers M135,
He and I worked on this truck for years and the biggest trouble is the brakes keep locking up.
We lost him a year ago last July and I just cannot give up on this truck, it is all for him. But I am so frustrated.
My Son and I have since replaced all the rubber flex lines, have cleaned all the metal lines. And they were all in very good condition.
Previously Dad and I had rebuilt or replaced the wheel cylinders, as well as the booster being rebuilt, twice. We thought that might be the trouble?
The brakes still lock up when applied for a short period. Just enough to make it really hard to drive.
Here is a thought??
I believe once someone on here said there are two ways to rebuild the master cylinder?? I remember Dad had it done once by a local mechanic. I think I was told there is a vent that must be modified from the rebuild kit??
Does this ring a bell with anyone??
Please help.
Thanks ever so much, Brad

 

[CMPPhil]

Hi Brad

Can you get a picture of the master cylinder and linkage? Ran into a simliar problem on Canadian MV and the cause and fix was so simple it is discusting. Has to do with linkage boot. I'll take moment and see if the TM section on the forum has your truck to see if it could be the same issue. Will also look for my pictures of the problem to see if the fix would apply.

Cheers Phil

 

[Brad]

Phil,
I have some additional photos I can send you if you give me your direct e-mail.
Mine is longhunter@digitalrazor.net.

I did try replying to the one the site sent me but then saw it said to NOT REPLY.

PS. notice the clutch linkage?? We had to convert to standard transmission due to much tranny trouble also.
Thanks,
Brad

 

[CMPPhil]

Simple but possible cause

Hi Brad

Had a moment to look at the manual for the M135-211 and it looks like the problem could be what I had on my CMPs which have a similar master cylinder.

What was happening was the Boot (C) was to stiff or to short and it holds the Piston (H) in so that it covers the Compensating Port (L) with that covered the brake fluid can not escape back into the and the brakes drag or do not release quickly. Stupid little problem but it took for ever to track it down. In my case the fix was simple shove the boot lip (B) further on the shaft so that it was trying to shaft back just a little, the problem went away.

Question for M135 & M211 owners do all of them have this design piston cup being a donut?


I have encountered some (marked as being M135) that had the single piece cup and piston like the design below.


Cheers Phil

 

[restlessrobie]

First pick is the original wheel cylinders which are no longer available (easily) second pic is a direct replacement which is far easier to obtain and a lot less expensive. I have both styles on my truck at this time as long as you do not mix them on a single axle you should be fine. I would make sure to use the same style per axle.

 

[CMPPhil]

Hi Brad

While I was responding you posted your photo, still could be the compensation port not always being uncovered when the brake peddle is released. When the brakes don't want to release have you ever hocked your toe under the peddle and pulled up?

Some 40 years ago where I worked had a contract refurbishing several M135s for Civil Defense, mostly it was just painting and cleaning but got to drive them and always enjoyed them. The automatic transmissions was good on all the ones we had but obviously more complicated than a manual transmission.

One further comment on wheel cylinders and master cylinders on all three of my CMPs I have gone over to having the cylinders sleeved that seems to be the end of brake problems now I just replace all the rubber parts every 10 years or so.

Cheers Phil

 

[USMC 00-08]

Hello Brad, great information from Phil and Erik. Another thing I would try to find out is if there is a check valve in your master cylinder. If you look at the master in the pic that Phil posted, you will see there is not supposed to be one. Reason being is that the check valve is in the airpak. If you have 2 check valves, the brakes will not release like they are supposed to or will lock up. I too have been working trough some brake problems and have it mostly solved now with the exception of a wheel cylinder that just started leaking.

When I first started sorting it out, I opened up the master cylinder and look what I found.



Yep...a check valve. It should look like this.



There is a possibility your airpak could be malfunctioning too. I may be wrong, but I think you might be thinking of how some of us have used an M809 series rebuild kit to rebuild these by using the 5 ton kit and the power piston out of the 5 ton airpak. The hard part is finding a power piston.

http://www.steelsoldiers.com/showthread.php?70703-M220-AirPak-rebuild

 

[USMC 00-08]

One further comment on wheel cylinders and master cylinders on all three of my CMPs I have gone over to having the cylinders sleeved that seems to be the end of brake problems now I just replace all the rubber parts every 10 years or so.

Cheers Phil

Welcome to the forum Phil! Where are you having these sleeved? I would be interested in having this done at some point. I kept all my old stuff when I replaced with new.

 

[hendersond]

I just met a guy who converts his GMCs to M35 air packs and master cylinders and swears by it.

 

[USMC 00-08]

Can you get us info on how this conversion is done? Very interested.

 

[CMPPhil]

First M135 I drove in 1972

Hi Brad

Here are the pictures I was talking about from 1972 - If I had not gotten involved with CMPs probably would have started collecting these.



Back the early 1970s a sheltered employment program I was running got asked to clean up some CD M135s basically steam clean and slop some paint on the rust spots, instead we taught the young men a little about spray painting. The CD people were surprised to get fully painted truck back, so they sent us more to do.

This was the first large MV I had ever driven.

Cheers Phil

 

[CMPPhil]

Welcome to the forum Phil! Where are you having these sleeved? I would be interested in having this done at some point. I kept all my old stuff when I replaced with new.

Hi

Thanks for the welcome, new to Steel Soldiers Forum but playing with MVs since 1979. When I rebuilt my first CMP HUP I kept finding NOS cylinders after having to replace them again 4 years later I went over to sleeving used White Post Restoration http://www.whitepost.com/ the next MV was a CMP C60L which I restored in 1990 sleeved all the brake cylinders, next truct 2007 CMP C60L same sleeved everything from the start. Since going to sleeves I have not had to replace any wheel or master cylinders. All I have done is replace boots, cups and hoses about every 10 years on each of the trucks. Oh yes still have all three trucks. If your curious take a look at my hobby web site http://canadianmilitarypattern.com

Have been enjoying the forum, just how really active, helpful and friendly it is.

Cheers Phil

 

[gentrysgarage]

You have a GREAT and informative site, I had found it awhile ago when was trying to get the 60L axles for my project, which was like the sound of crickets, at least with the M135 axles its wolves in the distance. I know they are out there...

 

[CMPPhil]

Hi

Thanks for the kind words on my Web page it was my way of sharing before Web Forum's like MLU & Steel Soldiers got going so strong as a source of shared help.

As to hard to find axle shafts, when I broke the 2nd axle (other side) I searched around and found company that make race care axles and axles for pulling tractors. Senter them a CAD drawing and the broken axle and about same cost a current truck axle they produced a new axle rated I think for 800hp.

Cheers Phil

 

[Brad]

Thanks to you all.
I will try your sugestions and get back to you .
Regards.
Brad Foust

 

[Brad]

Guys,
After looking that scematic of the master cylinder over....
Could it be that if I adjusted the linkage shorter it would pull the piston back a little farther and therefore uncover that compensating port??
Any thoughts???

 

[hendersond]

Yes, Watch for rust in the last little bit of the bore. It may not allow the piston to return all the way either.

 

[Brad]

Well friends, I tried adjusting that linkage.
Seems I had it almost as short as it would go.
But I took it apart and cleaned it all up and got it as short as possible. Right up tite inside itself and tite. No more to get without grinding some off the end of the thread and I dont want to do that unless ya'all think it might help.
As a result now after only a short drive and limited breking opportunitys I do think it is different??
Seems to be releasing quicker, though when I first applied the brakes the first couple times the front drivers wheel did grad hard and slide, but thn released pretty quick. Seems quicker than before.
May be another problem causing the grab?? Amybe rust from sitting??

Here is a thought?? What do ya think??
In my many trials in adjusting these brakes trying to keep them from locking up I think I remember adjusting them way back.
But in actuallity maybe being way back might that cause then to try and bind somewhat on their way back into the wheel cylinders??
I hope ya understand my thinking?? What would keep them from getting crocked and maybe binding some??
Thanks as always
Brad

 

[m1010plowboy]

I wish I could haul the local G749 Posse down there and help with the truck. It sounds like she needs to be dragged out behind the shed for a good whipping. The boys would have that deuce torn apart and put back together before you and I finish our ninth beer.

Out of the three trucks in the picture, the two on the outside both had the same symptoms this summer that yours did. The brakes locked up and wouldn't release. Goat, on the left and Gizmo on the right gave the pilots a real hard time but these guys don't get frustrated, they get even.

They're the kind of guys that say, "It's just nuts and bolts" or "It's just electrical, don't let it outsmart you". The immediate/ temporary solution to get them back to the motor-pool was do what you did, back the brakes off so the truck would roll. Backing off the brakes didn't seem to cause any of the problems you're having.



The solution for stuck brakes was to make the air-pak look like this. We had one NOS air-pak on the shelf for Gizmo and the Goat team tore into this air-pak until they won the battle. Goose hasn't had this problem yet and the only thing I may have done different than the Goat and Gizmo boys is drain the air-tank after every run and oil up the air-pak with air-tool oil 5 times in the last 5 years.



It sounds like you're getting to know Dad's truck real well so why not put it up on stands and do another inspection and/or repair on the wheel cylinders. I'd check over the Left front first because that's usually the problem when the right front is locking up.

We've all accepted that these old girls are high maintenance and after a guy takes the hubs off a few times, it just gets easier. After sitting, she probably wants her bearings greased, the backing plates painted and a few new wheel cylinders. Take is apart, put it back together and get it done before Friday night so we can go cruising!

Well friends, I tried adjusting that linkage.
Seems I had it almost as short as it would go.
But I took it apart and cleaned it all up and got it as short as possible. Right up tite inside itself and tite. No more to get without grinding some off the end of the thread and I dont want to do that unless ya'all think it might help.
As a result now after only a short drive and limited breking opportunitys I do think it is different??
Seems to be releasing quicker, though when I first applied the brakes the first couple times the front drivers wheel did grad hard and slide, but thn released pretty quick. Seems quicker than before.
May be another problem causing the grab?? Amybe rust from sitting??

Here is a thought?? What do ya think??
In my many trials in adjusting these brakes trying to keep them from locking up I think I remember adjusting them way back.
But in actuallity maybe being way back might that cause then to try and bind somewhat on their way back into the wheel cylinders??
I hope ya understand my thinking?? What would keep them from getting crocked and maybe binding some??
Thanks as always
Brad

 

[metal magnet 1963]

Seems like I am back here every year at about this time.
I been trying so hard to get these brakes right on my late Fathers M135,
He and I worked on this truck for years and the biggest trouble is the brakes keep locking up.
We lost him a year ago last July and I just cannot give up on this truck, it is all for him. But I am so frustrated.
My Son and I have since replaced all the rubber flex lines, have cleaned all the metal lines. And they were all in very good condition.
Previously Dad and I had rebuilt or replaced the wheel cylinders, as well as the booster being rebuilt, twice. We thought that might be the trouble?
The brakes still lock up when applied for a short period. Just enough to make it really hard to drive.
Here is a thought??
I believe once someone on here said there are two ways to rebuild the master cylinder?? I remember Dad had it done once by a local mechanic. I think I was told there is a vent that must be modified from the rebuild kit??
Does this ring a bell with anyone??
Please help.
Thanks ever so much, BradView attachment 647586

Hello sir,
Sorry to hear about your problems with your late fathers truck, It should be something good to remember, not a source of frustration. Did you ever try to remove the electric brake lock (emergency brake) and bypass it to see if you have an issue with it? You didn't mention repairing or replacing it, so I was wondering. Just give it a try and see what happens.