Rear Brake Reservoir

[Finally Mine]

Noticed that I am constantly having to add brake fluid to the rear brake reservoir on my 78 FJ40. Have gone through the lines with a fine tooth comb and can't find any leaks or have not noticed fluid in the drums. Had my son pump the brakes and noticed a great deal of brake fluid level fluctuation in the rear reservoir. Also that the top of the cover is wet, compared to the front one which is dry. Will replacing the rear cover help or is there something else causing this?

 

[antFJ]

Sounds like fluid is leaking out the back into the booster

 

[handcannon]

If it is leaking into the booster the brake fluid will eventually damage the diaphragm in the booster.

Don

 

[DougAustinTx]

You can see a "great deal of fluctuation" in the rear drum fluid level when actuating the brakes if your rear brake shoes aren't properly adjusted close to the drums. If the brake shoes are having to move a greater distance, it takes more fluid to pump them into position. When you release the pedal, all that fluid rushes back into the master cylinder due to the springs pulling the shoes back to resting position.