Hey all.

I've been slowly loosing break fluid in my 1968 f250 Camper-Special/Ranger.

In the master cylinder, the rear resevior stays nice and full, but the FORWARD resevoir will empty out.
I think the forward resivoir is connected with the REAR BREAKS?? Is this true?

I dont know much about break systems, but would like to get this baby on the road by next weekend. If I add fluid to it and purge it through... the breaks work fine for quite some time, and i dont loose too much fluid.

Any tips on where to find the leak?


Thanks a million! My life depends on it.

I also got a **** tun of weight in the bed, in the form of an old slide-in truck camper.


the above image is the type of cylinder i have.

 

Same deal here with a 69 F250 . I can never find a leak . After a mounth or so of not driving it I always have to check it .

 

The master cylinder can leak into the P/B booster where the fluid is hidden from view.

 

Funny story (now), years ago I had the same issue in a 1 ton with a camper. Took the girlfriend and her kids to the desert, the kids were in the camper, stopped at a stop sign and the rear of the truck disappeared in smoke. Holy sh-t!
The kids are in the camper and they are going to die! Jumped out of the truck, ripped open the camper door, scaring the heck out of the kids, no smoke in the camper. No smoke anywhere, truck running just fine, no leaks, no sign of anything awry. The smoke didn't smell electrical, or oily, or camperish and it was gone. Rather unnerving to say the least.
I asked around different mechanic types and finally my old friend Benny told me the brake fluid that was built up in the power booster made it way in to the engine where it burned off making a cloud of smoke. Ah Hah!
6 months later while hauling a trailer with 2 cars on it traffic stopped in front of me, when I stomped on the brakes the power booster quit with a whoosh, I got her stopped with both legs, barely.
My advice? Replace your master cylinder and power booster as a unit. Before you too have a kind of funny story to tell.

 

The forward reservoir is connected to the rear brakes. Use a pedal jack or have someone step on the brake pedal (Truck does not have to be running.) and crawl underneath to see if any signs of leakage.. Especially around the rear brake backing plates. Sometimes you can check to see if the booster is leaking by seeing if there is any brake fluid in the booster vacuum hose, sometimes.
It's "normal" for the rear of the master cylinder to have the level of the fluid go down as the pads wear.

 

Older thread but it does bring up a question. If the Master Cylinder does leak into the brake booster,.... Wouldn't it affect the fluids in both resovours?

 

there is a seal between the front and rear reservoirs also. so it can leak from one to the other then out the back into booster or any combination.