What is brake fluid and which one should you use for your Transit 350?

What is brake fluid and which one should you use for your Transit 350?

In short:
Brake fluid is the fluid by which the force applied to the brake pedal is transmitted to the brake pads.
The brake fluid must always be at the correct level so that there is no loss of stopping power, and you must only use the one recommended by your car’s manufacturer.
If the brake fluid level is low, the dashboard brake warning light will come on. You may also notice that the brake pedal feels “spongy”.

The recommended brake fluid is usually engraved in the cap of the master cylinder reservoir. If you do not find it there, you should check the owner's manual of your Transit 350.

There are many types of brake fluids, and all of them have been rated according to the DOT regulations. It is important that you use the recommended brake fluid for your car and do not mix different brake fluids. If you mix them, their properties may be affected, and they will not function the way they should.

The higher the brake fluid’s DOT number is, the higher its resistance to high temperatures.

  • DOT-3: it is for conventional brakes. It is hygroscopic (it absorbs water).
  • DOT-4: it is for conventional brakes and cars with an Anti-lock braking system (ABS). It is less hygroscopic than DOT-3 brake fluids.
  • DOT-5: it is not hygroscopic but it absorbs more air than the others.
  • DOT-5.1: it is DOT-4’s enhanced version. It is hygroscopic. Since its viscosity is very low, it may leak if the braking system is not in perfect condition.

When should you refill the brake fluid?

When the brake fluid reaches the minimum level recommended, the brake warning light will come on:

You can also realize that the brake fluid is under the recommended level because the brake pedal feels “squishy” when pressed. That is to say, its pressure diminishes and your car takes longer to stop.

If you notice these signs, you have to check the master cylinder reservoir. This reservoir can be found close to the engine, and it is usually white.

Air and water can contaminate this fluid and damage its properties, therefore reducing its stopping power. If the brake fluid level is low, air may get into the circuit, and the brake of your Transit 350 will stop working altogether, which can be dangerous.

If you have to refill the master cylinder reservoir, consider the following information:

  1. This liquid is very corrosive, irritating and it is also toxic, so you should always handle it while wearing gloves. Do not let this fluid drip into paint or any plastic items because it will corrode them. If this fluid is spilled, wash it with abundant water and dry the area.
  2. Make sure that the brake fluid reservoir is properly closed. If it is not, it may get damp and lose its stopping power. Moreover, the braking circuit may also get corroded.
  3. Make sure that the brake fluid level is always between the minimum and maximum marks.

⚠️ Warning: if you used a brake fluid that was NOT recommended by your cars's manufacturer, you will have to empty the master cylinder reservoir and replace the brake fluid. An auto mechanic should be the one who does this.

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Ford Transit 350 problems: brake fluid



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