Brake fluid mystery???

[cbvet]

I've done a lot of brake work over the last 49 years (since I was 13) , so I generally know what to do when there is a problem. But this time I'm not too sure.
My buddy drives our '52 M35 all the time, so I never really look it over. He swears that before our last parade he topped-off the master cylinder. (He is a former Marine that likes his Old Style, though) Since then he's traveled about 90 miles.
Master cylinder was dry today, with NO sign of a leak at wheel cylinders, hoses or steel lines.
Filled it up & bled system. No pedal. Replaced master cylinder & bled. Great brakes.
But where did the fluid go? Can fluid leak into the air pack? I've never had one apart.
I know that on the old Hydrovac vacuum assist boosters, it was not uncommon to have brake fluid leak through the diaphragm & get sucked into the intake manifold, causing heavy smoke.

Any thoughts?

And who on SS has master cylinder rebuilding kits for sale?

Thanks guys!

 

[gimpyrobb]

PM sent.

Yes fluid can get in the airpack's can.

 

[Wolf.Dose]

As gimpyrobb said, yes, it can. And this is not a typical Deuce problem. These problems also come up with European made trucks of the 50's and before like on a L5000 Daimler-Benz (a beefed up L4500 from WWII) or on a KHD Jupiter 7 t truck from the German Army. The diaphragm dries out somehow and than gets leaky. It is basically a quality problem of the material. The mixtures these diaphrams are made of is not always 100 % the same (like coulor mixings are not 100% identical even with the same recipe). Some fall leaky, others never, some recover, some don't. You simply have to live with it.
Wolf

 

[cranetruck]

Eric, the slave cylinder piston (4) is driven by a rod from the air cylinder, if the seal cup (1) leaks, fluid will enter the air chamber. Image courtesy gringeltaube.....

 

[roger-wilco-66]

I've had the same issue with my deuce. Leaked into the airpack. It eventually blew the fluid out of the air-pressure vent near the airfilter when releasing the brake, that's how I first noticed it...
I rebuilt the airpack, now it's fine.



Cheers,
Mark

 

[Brock Steel]

Air pack backup fluid reserve. I like it.

 

[cbvet]

Thanks very much all!
I guess I'd better locate some kits & start rebuilding them, as my newest deuce is 39 years old.

 

[Brock Steel]

Ebay has them 10 bucks.

 

[Wolf.Dose]

Roger-Wilco-66 said how to do it, besides the problem which happens to any of the air over hydraulic systems. I forgot a relatively new truck, the MB 1017 which struggles with the same problems sooner or later.
Wolf