Brake reservoir


I went out in the field man today its on a L plate, on the way home i noticed a light on the dash board it was a red circle with a sign like this ! inside it. After having a look around i noticed that the brake fluid was low infact very low, after removing the cap there seemed to be a ballon hanging off the cap. I dont think this is supposed to be like this, it looks as if the rubber liner in the cap as been sucked down in to the reservoir which looks like a ballon. Am i right in thinking this, and has anyone had this happen to them.Thanx Barry.

Loss of fluid.

The baloon is probably the brake-fluid-level-indicator switch which when lowered indicates the brake fluid level is lower than minimum level. The switch floats on the brake fluid. If you top up the reservior the dash light will go off.
What you must do is visibly check the entire brake system to find the leakage. Fluid is probably leaking from a rear brake slave cylinder. The brake drums need removing to do the visible check. If the slave cylinders appear dry then look to the front disc caliper brakes and then check the all the brake pipes/unions including the master cylinder.
If would be foolish if not dangerous to drive the car without sorting the problem. Most vehicles are duel circuit and loss of fluid in one circuit will mean you have minimum brake efficiency and possibly in danger of accident.


The rubber you describe serves two purposes, it keeps muck and debris out of the fluid, and activates the warning light switch. This condition is normal for a reservoir with low fluid, it is vital to find out if the fluid level is due to low disc pad and low shoe linings, or leakage.

If this balloon activates

If this balloon activates the warning light, How does it do this as there aint any wires running to the cap. Also the balloon nearly fills the reservior. So i would imagin that i wont get alot of fluid in the reservior while this is in there.Do i need to replace with a new cap. I checked for leaks (no signs), I did notice the pads in the front are low through the holes in the front wheels though.
P.S can anyone post a pic of the inside of their cap off their reservior please, just so i can see if the way i have explained this is correct.Thanx Barry.


Two types of caps were fitted, one should have two wires running to it, the other does not, the rubber holds a small metallic element within it.
As well as functioning as a washer to keep out debris, it acts as a magnet to hold the switch, contained within the cap in position. Once it lowers, the magnetism force deminishes and the switch closes, this activates the dash light.
Some earlier types had a small plunger which sat on top of the washer, if this dropped too low, this activated the light.

Many vehicles had caps replaced with earlier types as they were cheaper, these were mainly damaged due to overtightening and cracking the cap.