2. Brake Fluids – Part 2

Let us discuss today; in Part 2, on “Brake Fluid” checking and some important tips.

How to check Brake Fluid:

1.     Contamination Check:

Brake fluids are miscible in water and the same can be used to check mineral oil.

  Steps involved:

1. Take a clean beaker with 100 ml water.

2. Remove a small amount of the suspect fluid from the reservoir. It is best to pull the fluid from the top of the reservoir due to the fact petroleum-based fluids are lighter than brake fluid.

3. Place the suspect fluid in a clear beaker filled partially with water. Stirred for 2-3 mins. and allowed to settle. If there is petroleum- based fluid in the brake fluid it will separate and float to the top.

If two layers form, then there it is a contaminated system.                 

2.     Boiling Point Check:

a.     Optical Refractometer:

An Optical Refractometer will clearly show the amount of moisture in the brake fluid. A small drop of fluid is placed in the tester, then the tester is held up to a light to read the amount of contamination. This tester is extremely accurate and shows both the percent of moisture and the boiling point of the fluid. 

b.      Electronic brake fluid testers:

Electronic brake fluid testers actually measure the fluid's boiling point. The test takes only about a minute and is quite accurate. If boiling point of the fluid temperature is getting dangerously low, replacement is recommended to minimize the risks of pedal fade caused by fluid boil. 

Brake Bleeding:

?        Bleeding is removal of air from the system.

?        Ensure to bleed the system perfectly.

?        Always use recommended brake fluid for bleeding the system.

?        Pedal sponginess is an indication of improper bleeding.

?        Brakes need to be bled whenever a hydraulic component of the brake system is replaced, or whenever your diagnosis indicates that air is trapped in the hydraulic system.

?        THE BLEEDING SEQUENCE: FRONT LEFT & REAR RIGHT AND FRONT RIGHT, REAR LEFT (Vehicles having ‘X’ split)

Brake System Flushing:

If evidence of contamination is present in the vehicle’s brake fluid, you need to perform brake system flushing procedures. Some common examples of brake fluid contaminants include mineral oil, engine oil, or transmission fluid. After flushing the entire brake system, replace the following rubber components:

           ? Brake hose assemblies

           ? Master cylinder rubber parts

           ? Brake caliper and wheel cylinder boots and seals

           ? Proportioning valves      

           Re-flush the system after all of the rubber components have been replaced. Once the second flushing procedure has been performed, bleed the entire system.

Important Tips:

?        Never handle rubber seals or internal parts of the brakes system with greasy hands.

?        Use Brake Fluid only for cleaning of master cylinders, wheel cylinders etc. Never use mineral oils like petrol, kerosene , diesel etc.

?        Seal swelling is due to the use of spurious brake fluid or use of mineral oil for cleaning purpose.

?        In case Spurious fluid is found inside the brake system, overhaul the complete system. Drain the fluid and fill it with fresh brake fluid. Change all rubber parts.

?        Don’t carry out water wash directly on reservoir / servo TMC.

?        Brake Fluid should not be exposed to the atmosphere.

?        Brake fluid is subjected to repeated heating and cooling cycles which can lead to gradual deterioration in properties. Hence it is absolutely essential that the Brake Fluid be drained and replaced in specific intervals..

?        Use transparent bleed bottle & pipe while bleeding.

?        Use separate container for brake fluid while dispensing out brake bleeding.

?         Brake Fluid should be stored in its original container in a clean, dry location at or below room temperature preferably separated from similar storage of petroleum products or fluid materials used for maintenance purposes. Under good conditions of storage, new, unopened containers of Brake Fluid, with their foil seal intact, will have a shelf life of two years

References:

• Websites related to Brake Fluids
• Wikipedia