What causes this brake system failure...?

[LiqTenEXp]

Little background info:

1970 M35A2 Kaiser-Jeep

Purchased the Deuce in April 2009. Bled all the brakes lines, booster, and MC with DOT5. I keep a constant eye on the fluid levels. Brakes have been excellent on this truck ever since.

After stopping on an incline yesterday I had no brakes. The pedal was like a rock, not like I've lost the booster but like stepping on a rock. I found this out as i was going down the other side of the hill and needed to slow down for a light. I downshifted a couple times and grabbed some parking brake to slow it down. After releasing the pedal and pumping it a couple times the brakes came back to normal. I pulled over after that and bled the tanks. Everything seemed back to normal.

I drained my tanks daily. When I drained them this time I noticed an EXCESSIVE amount of water in the inboard tank. I would expect this one to have more water since it is the "wet tank". Other than that I couldn't see any leaks of fluid or air around the booster or any of the lines under the truck. Even after draining the tanks I had it happen 2 more times on my way home for a total of 3 times.

Anyone else have this happen? Did I get some form of hydro-lock or is this a sign of future brake problems to come?

 

[rlwm211]

I cannot offer any specific answer. I know from my experiences that cold weather increases the amount of moisture that will accumulates in a trucks air system. Any moisture in an air assisted brake system is a danger especially in cold weather. Air lines can freeze and any air acccuated device can freeze and not operate at all.

I would recommend blowing the air tanks after every use in cold weather. If you are engaged in a long distance run, I would blow the tanks periodically during the day to prevent moisture buildup.

I hope some of the more sage and wise Deuce operators can offer more insight in this unusual situation that occurred to your truck.

Sorry I can't offer more help on this

RL

 

[Floridianson]

Airpack hung up try oiling heavy.

 

[73m819]

ditto

 

[m16ty]

Was it below freezing when this happened? From the amount of water you said came out of the tank I'm going to say you have some ice in your air system.

You could even have ice in your hyd system. DOT5 dosen't absorb water and water can collect in a low spot in the system if there is moisture in there. That could also explain as to why the pedal seemed harder than just no boost.

 

[bugei]

did you recently rebuild your airpack? this sounds very much like the issue if the piston cup is put in backwards. WARNING!!!! the tm is WRONG!!!!!

this is the link to the old forum sticky re: this issue. warning, read this carefully, make sure you know which pictures are CORRECT, it is a bit misleading sometimes

View topic - Airpack Rebuild Warning. :: Steel Soldiers :: Military Vehicles Supersite

btw, dueces with no brakes are pretty darn exciting, huh? glad you tested the e-brake aren't you?

 

[jwaller]

when did you last lube/oil the airpack? it has a square head plug on the rear just for this. could also be an allen head.

 

[ctmustang]

on oiling the airpack. Especially in cold weather. Pop out the plug on the rear or in my case the j pipe and shoot in some airtool oil. Should at least keep the piston moving. Should probably do this 2-3 times a year.
Just my 2 cents.
C.T.

 

[tm america]

good idea i guess i need to oil mine to.oh my green god a tm is wrong?what will all the tm guys do now i'm gonna need my popcorn for this oneok now i'm getting mad where did you guys put the popcorn smily

 

[Keith_J]

Certainly was ice in the booster, causing the air piston to hang.

 

[m16ty]

You could even have ice in your hyd system. DOT5 dosen't absorb water and water can collect in a low spot in the system if there is moisture in there. That could also explain as to why the pedal seemed harder than just no boost.

Does anybody think this could be remotely possible? When I posted this earlier it just kind of came to me as I was typing. If water collects in low spots in the system using DOT5 like they say I think this could be a real possibility in freezing temps.

 

[tm america]

really possible but to do it to all wheels at once i would think not maybe water freezing in the mc not letting the piston move .the wheel cylinders would move even with ice in them the pressure on them would brake the ice fairly easily
​

 

[Keith_J]

Does anybody think this could be remotely possible? When I posted this earlier it just kind of came to me as I was typing. If water collects in low spots in the system using DOT5 like they say I think this could be a real possibility in freezing temps.

It would just cause problems with 1-2 wheels. There would be more brake fluid volume for the others.

This is water in the air side, causing the air piston to stick. No movement in the air piston means no fluid movement and no brakes.

 

[mckeeranger]

.oh my green god a tm is wrong?what will all the tm guys do now

I've found mistakes in the TMs too. TM 9-2320-260-34-1 has a table showing the order you adjust the cylinder valves and injector valves in relation to the piston positions. If I had not realized something was wrong, I could have popped the nozzles off the injectors on all 6 cylinders.

I wonder if I should fill out the corrections form in the back and send it in?

 

[Keith_J]

A little methanol in the air tanks will keep the system running in cold weather.

 

[Keith_J]

I've found mistakes in the TMs too. TM 9-2320-260-34-1 has a table showing the order you adjust the cylinder valves and injector valves in relation to the piston positions. If I had not realized something was wrong, I could have popped the nozzles off the injectors on all 6 cylinders.

I wonder if I should fill out the corrections form in the back and send it in?

What are "injector valves" and how would one go about adjusting them?

I know about pop-off pressures in the injectors but this isn't something covered in the -34 for the engine.

 

[m16ty]

really possible but to do it to all wheels at once i would think not maybe water freezing in the mc not letting the piston move .the wheel cylinders would move even with ice in them the pressure on them would brake the ice fairly easily
​

It would just cause problems with 1-2 wheels. There would be more brake fluid volume for the others.

This is water in the air side, causing the air piston to stick. No movement in the air piston means no fluid movement and no brakes.

Ok, I'm not saying either one of you are wrong. I'm just trying to figure this out better .

If the air piston is frozen it would be the same as no air in the system, right? I say this because I don't think the piston moves when you apply the brakes with no air in the system either and you still have non-boosted brakes.

This statement in the orginal post "The pedal was like a rock, not like I've lost the booster but like stepping on a rock." is what got me to thinking it could be something besides the booster being stuck.

Maybe I'm wrong. It won't be the first time .

 

[tm america]

there is a valve in the airpack that is moved by the pressure going to the airpack from the mastercylinder it opens letting air in to the cylinder to force the booster to move if it freezes it can not let fluid in the airpack move thus hydro locking the mc or the mc can freeze giving you the same effect rock hard pedal and no brakes not just hard brakes

 

[m16ty]

there is a valve in the airpack that is moved by the pressure going to the airpack from the mastercylinder it opens letting air in to the cylinder to force the booster to move if it freezes it can not let fluid in the airpack move thus hydro locking the mc or the mc can freeze giving you the same effect rock hard pedal and no brakes not just hard brakes

OK, I wasn't thinking about the valve . I was thinking of just the air piston stuck.

 

[coyotegray]

when did you last lube/oil the airpack? it has a square head plug on the rear just for this. could also be an allen head.

What type of oil should be used to lube this..?

Thanks,
Andy.