Master cylinder back pot empty

[DUSTERDOWNS]

I got a 1970 340 Duster. It has front disc brakes that are factory. went for a hour ride yesterday and when I got home I went to park it and the pedal went to the floor. Pulled the cap off the master cylinder and the front pot was full of fluid but the back one was empty. check under the car and there is no wet spots or any signs of fluid leaks,inside tires are dry as are all lines . I am open for any suggestions or help you mopar GURU's can send my way, thanks Steve.

 

[hemi71x]

You have a power brake booster?
Then the fluid is going into the booster.
Bad master cylinder.

 

[Leadfoot]

You're just going to have to fill and bleed. Then have someone pump and hold the pedal while you inspect the lines. There's really not too many places for it to go. Also, press and hold the pedal. If it holds for a second or two and then goes to the floor you may be leaking out the back of the MC and running down the firewall on the inside or the outside of the car. Check your carpet .

 

[mguner]

Either it is in the booster or in your floor board being soaked up by the carpet. Check the inside of your firewall.

 

[DesertRat]

back pot = front brakes

 

[rigger3006]

maybe check proportioning valve, dealing with rotten lines on wifes 72 duster at this time in that area

 

[nm9stheham]

Either it is in the booster or in your floor board being soaked up by the carpet. Check the inside of your firewall.

That is the likley spot...if it did go into the carpet, the carpet should all come out and be thoroughly cleaned and all the fluid removed from everywhere. It is hard to tell how many floors have rotted out due this type of leak. If you are not aware, brake fluid absorbs water and will hold it against sheet metal.

 

[BillGrissom]

Also, brake fluid is a great paint remover, which is why most cars are rusted below the master cylinder and often inside the cabin if manual brakes. DOT 5 (silicone) doesn't eat paint.