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The Ins and Outs of brake fluid

Published on July 14, 2011 under Humble Mechanic

A fan asked me if he could do his own brake fluid service.  I responded to him with ” sure it’s really easy”.

The more I thought about it, the more I realized that there is actually a lot to servicing brake fluid.  There are lots of tools out there that can help you with this.  At the shop I use a pressure bleeder.  It pushes fluid through and works great.  That machine is about $1000, so not something you want to run out and buy.

As I have said before, brakes are a VERY important safety system.  I can’t be responsible for anything getting messed up. I don’t want anyone getting hurt, so please take this seriously.

Ok, brake fluid, this is the main connection from your foot, to the brakes at the wheels.    When the brake pedal is pressed, it forces fluid to the brakes. This moves the piston and pushes the brake pad into the rotor or brake drum.

We need to keep this fluid clean for a couple of reasons:
1)   Dirt in the lines can cause damage to seals in the system
2)   Brake fluid absorbs mositure(hygroscopic). Excess mositure will boil when the brakes get hot or freeze when they get cold. Either way this can result in expensive brake system repairs

Let’s get the fluid changed.  Remember,  this must be done correctly, or your brakes will be very sad.
There are several ways to do this I will talk about the 2 easiest ways to do it, and all you will need is a helper and wrenches to open the bleeders.  I personally like to take the wheels off to flush brakes.  Brake fluid on nice wheels can ruin the finish.

Gravity Flush
This takes a long time, but is the easiest way, and has the lowest chance of air getting in the system.

First, open the brake fluid  reservoir, and fill it to the top.

Next start by opening the bleeder fitting on the brake that is furthest from the brake fluid reservoir. This will usually be the right rear brake.

Open the bleeder screw enough to let fluid come out.  Keep a close eye on the fluid reservoir, it MUST NOT empty all of the fluid out.  While keeping the fluid full up front, let gravity do the work.  When the fluid is clean, close the bleeder, clean with brake clean, and move to the other rear wheel.  Do the exact same time on the 3 other wheels.

This takes a really long time, just don’t touch the brake pedal, and everything will be good.

Manual Flush

Well, this way is much faster, but you will need a helper, and run a higher risk of air getting into the system.  This way uses the pressure created by pushing the brake pedal to force the fluid out of the bleeder.

Like with Gravity Flush, make sure the fluid reservoir  is full, and DO NOT PUMP IT EMPTY!

Start at the futherest wheel from the fluid reservoir.  This time, have your helper pump the brake several times. Have them hold the pedal to the floor.  Open the bleeder and let fluid out.  Now close the bleeder, and have your helper pump the brake again.

This will need to be done a few times at each wheel.  Again until the fluid is clean.   Please be really careful. When the bleeder is open, DO NOT let the brake pedal come off the floor.  This will suck air in to the system, thats what happened to me the very first time I did it this way.

I have several times in this post to be carful. If you happen to get air in the lines, it will feel like your pushing down on a sponge.  This feeling gets worse as the brakes get hot.  PLEASE don’t do this if you are not 100% sure!!!  I can not be responsable if you damage your brakes.

 

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