Where did all the brake fluid go?

Nine years ago I replaced the brake hoses on my 78 XJ6C and bled the brakes with Castrol LMA…everything was fine. Life happened and I have not driven the car for seven years.

Last weekend I wanted to drive it, so I started it up, and the brakes go to the floor.

The remote brake reservoir was almost empty. There are no signs of fluid on the driveway or calipers; there is no fluid on the driver sides floor; the top of the reservoir was on tight; with the car running and pumping the brakes the engine almost dies; the check valve that goes from the brake booster to manifold vacuum is dry on both sides and holds vacuum; I added fluid because I have a case of Castrol; and still not brakes.

Where should I start?

  • Bleed the brakes
  • Pull the calipers off
  • Pull the master cylinder

Here is a video of what is going on.

Its in the booster…M/C seals are gone

So I did some more research and here is what I found:

  1. I pulled the red nipple off of the brake booster and used my bore-scope to look inside. This was my first time ever seeing inside of a brake booster (didn’t know there was a giant spring in there) and didn’t see a bunch of fluid…although it was hard to see the lowest point of the booster. Here is a video - click picture:

  2. I did some testing with the vacuum line disconnected and my finger over the red nipple. With the car running, when the brake pedal was depressed air was forced out of the nipple. If I kept my finger over it, there was good pressure at the pedal.

  3. When I kept my finger over the red nipple and the brake was returned to the up position, I didn’t feel much suction on my finger. Is this suppose to happen? When the brake was depressed again and I kept my finger over the red nipple, there was pressure at the pedal.

messing with the booster and the vacuum line did change the pedal pressure.

Any new thoughts?

  1. If there was any fluid in the remote reservoir, there was adequate fluid in the master. My first thought was leaking seals on the piston in the MC. But, if I get it right, the brakes are back???

  2. The booster reacts to vacuum from the engine, but does not create vacuum .

  3. The one way vacuum valve leaks??

4 After a long period of inaction, a BF flush may be indicated… .

5.Most mechanical critters do not like to be inactive… others as well… us!!!