'94 brakes: loss of fluid in small reservoir

[astro44]

I have a 94 AWD w\ABS and the smaller of the two reservoirs on the master cylinder will not hold fluid. My brake light came on (not the ABS light) and will not go off. Obviously leaking from somewhere. Larger reservoir maintains normal fluid level.

I have done the front brakes and noticed no leaking. I have check the outside of the rear drums but have not pulled them apart. Any thoughts on what may be causing the leak? checks ? tips ? What function do the two different size reservoir have ?

Please help this backyard mechanic ! thanks

[CD Smalley]

You got a rear brake cylinder that's leaking. Take the drums off and you;ll find it.

[astro44]

I did have a bad cylinder. thanks for the quick and accurate response. I went ahead and replaced it. That's the good news. The bad news is as I was bleeding the brakes I developed a leak in the main brake line to the rear brakes. Unfortunately the leak is above the gas tank.

In order to replace the line I can break into it about at the drivers door and then the next spot is where it Tee's off at the rear axel. With my mechanic expierience I'm not sure if I want to attempt to drop the tank or just bypass existing. Any suggestions would be appreciated. I will be prowling this database to see if I can get some insight on tank removal and\or brake line replacement. thanks again.