The Land Rover Writer

Friday, February 3, 2012

Disappearing Brake Fluid

While the Monza remained a delight to drive, it did exhibit an odd behavior. Any time the car sat for a while at the ferry terminal on the mainland, it seemed to lose brake fluid in the master cylinder reservoir. 

Normally, on a single circuit drum brake system, you lose brake fluid through leaks in the wheel cylinders or at a line. If it's at the wheel cylinder then the fluid leaks onto the drum, the shoe slides and the brake seems to grab or lock up. If it's a line the fluid level goes down only when you push on the pedal.
This time, the fluid level decreased just from sitting. Since the master cylinder is the only part of the system with constant pressure, it had to be a master cylinder leak.

Again normally, the master cylinder shows a leak by slowly having the pedal go to the floor under braking. If it's an internal leak [the more common] you don't lose fluid as the fluid simply pushes through the internal seals. 

This time is clearly different but all the experts agree the leak is in the pushrod seal of the master cylinder. Only two nuts, accessible through the front trunk, hold the master cylinder in place, so the job should be easy [!]. Bench bleed the cylinder, install a new line from the cylinder to the block connector, tighten up the nuts, and that should be it. Hopefully I can get to the mainland next week to complete the job.


  1. Good thing you were able to spot the problem right on! Leaks on transmission and brake reservoir are not good for you and your car. When the brake fluid starts to leak, there will be not enough fluid in the cylinder or lines to multiply the force of your foot into the brake pedal, and it will be difficult for you to control the vehicle. But I think by now, your auto has been checked and repaired. How was it? Well, just be sure to check the brakes and the brake reservoir in order to detect if there are any issues on the brake system. Drive safely!

  2. Thanks, Michelina. I actually wound up replacing the master cylinder and removing all the wheels to be certain that I have no wheel cylinder leak. I might have a very small seepage past one cylinder, but with the new master the brakes work fine now. I do check the fluid level every time before using the Corvair.