Brake fluid Question

[Kaiser67M715]

So, I drove the deuce to work, everything checked out this morning, good air, except my air buzzer has never worked, but for whatever reason at full pressure it started humming-seemed like a vent on the side, I tapped it, noise went away...anyways going through I check tire pressures, make sure my brake fluid reservoir is full, oil pressure is good, no extra leaks etc.

Well this afternoon, I went to go leave work, and noticed my brake fluid was low(was fine when I arrived this morning, I always do a post run walk-around as well), like almost a half inch(just a couple ounces)...so I pumped the brakes, felt fine, looked around for leaks couldn't find anything, none of the slots at 6:00 in the backing plates had any fluid(not that that is any real indicator for a few oz's). Figured I had to get home, not paying $300 for a tow, so I'll go the back way-very little traffic, and being all uphill, any stops should be fine. I got it home, brake pedal felt fine the whole way home, checked the level in my remote reservoir to see if I lost more, and I got back the brake fluid I had "lost".

WHAT happened???? Should I pull everything apart??? or run it and see if it happens again-I don't really think this is wise but if no one else knows what happened it might just end up being the case, especially if I can't see anything visually under the truck. I'll report back tomorrow, if it is low in the morning again.

Fluid is DOT 5, purchased from Iris Industries, less then a year old. Everything in the brake system was rebuilt or replaced last year. And everything checked out at the beginning of this year- no leaks; pulled back boots on wheel cylinder, clean and no fluid.

any thoughts are appreciated.

 

[Eaglhawk]

I have had similar strange things happen to my m35a2 and others... I think the hydro-pack (air over hydraulic) piston/diaphragm is not moving fully back keeping a little fluid inside itself. I found the more you regularly use the truck these problems go away.

 

[Kaiser67M715]

No visible leaks, and an update on what seems to be happening,

I checked it this morning, was low, maybe a 1/4" not as bad as yesterday. Got home later(did not drive it, so it sat all day in the same spot) it was full. this mornings temp was about the same as yesterday morning, but much less humid, so it was a cool 65 degrees, rather then a muggy 65 degrees. afternoon temps were about the same, BUT I had parked the truck in the shade at work, so it stayed cooled, and the humidity was actually less during the day yesterday then today(more humid today)so at the very least it seems to be temp and humidity sensitive, (so cool and less humidity= less fluid), oh and both times I let the air sit, I drain the air only every other use(or if I know I won't use it in the next two days)

and if what Eaglhawk says is true, then maybe the temp change and humidity are playing with the pressure in the air pack allowing the fluid to appear like it is missing.

 

[4x4 Forever]

Please get the air buzzer fixed/repaired/replaced, I'd hate to see someone loose air and brakes and take out a minivan...

 

[3rdmdqm]

Mine has done the same thing. Very strange. Depending on the weather the level seems to change. Can't find any leaks and fluid seems to stay close to full but fluctuates on the remote reservoir.

 

[Kaiser67M715]

It was very humid today, and very hot, fluid level was actually a little high, tad above the line on the remote reservoir. I'm almost wondering if the heat is affecting the hose(rated for dot 5 fluid, extreme temps etc) and it feels and looks fine(doesn't have any cracks when pinching it). But I wonder if the temp swings(60's at night, 90's during the day) are causing the hose to expand and contract. There is about 3ft of hose from the res to the master.

And yes I am working on the buzzer, but part of the thing I learned driving was to watch the road, check mirrors, look at road, check gauges. And I always look at my gauges before arriving at a stop sign.

Also I check it more frequently in town because I limit my speed and distance between cars more.

I had lost one airline before and while the compressor was able to maintain pressure, every time I used the brakes it would drop. And I know I can stop the deuce with no air, but it takes a lot of pressure, and it certainly takes longer(tested going downhill on a dead end rd)


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[Aussie Bloke]

G'day everyone,...


Funny thing is I have this happening to me with my Deuce.

I go collect my Deuce from where I have it stored and do my pre trip checks,...

The remote reservoir has all but 1 time needed to be toped up, I have to put in at least 1/4, the most I had to put in it was a FULL refill of the reservoir.


There is NO sign of where it is going,... and I mean NO sign, so far I have used 2 500ml bottles and I will be getting those replaced next week so I'll have some on hand.


I am thinking maybe the seals in the airpac might be leaking and its getting vented through the airpacs vent system hence why I don't see where it is going,....?

I can let it sit overnight after driving it and there will be NO loss of fluid but leave it a week or more and when I get back to it the level has dropped.


Thoughts?



Aussie.