"I couldn't find the sports car of my dreams, so I built it myself"

- Ferdinand Porsche

Flushing the brakes

By: Bill Jones

Overview

The brake system should be flushed every 2 years to maintain performance and longevity of the components. One of the main reasons is due to the fact that your brake system operates at extreme temperatures. The process of flushing the brakes is nearly the same as bleeding the system with the exception of the amount of fluid necessary to complete the job. You can do the job with minimal tools or purchase some specialty tools to make the job much easier. The process is basically the same either way and applies to your Porsche as well as any make and model for that matter.

Tools needed

Wrench for bleed screw (don't skimp here! its no fun dealing with a stripped bleed screw. Purchase a proper wrench, Snap-On, MAC Tools, etc.)

Clear rubber tubing (sized to fit over the nipple of the bleed screw) and a catch container for the old fluid

1 qt Brake fluid of your choice (we will discuss the differences later in the article)

A helper to push the brake pedal on command

Jack and 4 Jack stands (or a lift if you have one)

Turkey Baster (not your wife's from the kitchen, she wont be happy when your thanksgiving turkey tasted like DOT4 brake fluid! Go buy one just for your use) The one in the link has a Silicon bulb with a glass tube and should hold up to brake fluid. You should try not to let the brake fluid enter the bulb to prevent any reaction or deterioration of the material.

Optional Tools

Motive Products Power Bleeder - European- Black Label  - This makes the job much easier and faster. It also eliminates the need of a helper. Once setup you can basically move from caliper to caliper without refilling the reservoir even. Available on Amazon for around $68. Money well spent in my opinion. You can use it empty as well but you will need to watch the fluid level in the reservoir and refill it several times during the procedure. They also have models specific to other makes as well as universal kits available. Just follow the above link

Genesis Cable Bleeder Bottle -  This is used to catch the old fluid that is pushed from the system during the procedure. It includes the clear tubing and has a nice cable to hang it from the cars suspension and prevent it from tipping over. Available at the link above for around $11.

Choosing a brake fluid

Not all fluid is created equal. The thermal load on the brake system is much different during your daily commute than on the race track. Once enough heat is generated in the brake system it can get to a point that the brake fluid will boil causing fade or even failure of the system. This is why understanding how you will be using the car will dictate what fluid you should be using. Lets take a look at some boiling point information for several brands of fluid

  DOT-3 DOT-4 DOT-5
Dry Boiling Point/deg F 401 446 500
Wet Boiling Point/deg F 284 311 356

 

Now lets take a look at some popular fluids used in high performance vehicles.

 

High Performance Brake Fluids
Boiling Points Dry Wet
AP Racing 550 531 261
AP Racing PRF608 608 390
Castrol SRF 590 518
Motul Racing 600 585 421
Ate Super Blue 200 536 392
Motul RBF 600 594 421

 

Looking at the chart above the AP Racing PRF608 clearly stands out. The is a superb fluid that is ideal for racing. It is not, however, recommended for street use. The fluid is not compatible with magnesium components and the resulting chemical reaction will surely cause failures to occur. So looking further we see the Castrol SRF brake fluid. This is a widely used fluid in the racing world as well. Safe for all non-mineral oil-based disc and drum brake systems it can be used in just about any vehicle. So why not just use it in everything you own? Well, at around $70 a liter it is the highest priced fluid in our comparison. Figure using at least one liter to flush your system and then pick up another to keep on the shelf. The SRF is compatible with other standard fluids but a full flush is recommended to get the most out of the product. The last two for comparison are prices at between $15-20. The Motul RBF 600 has a slightly higher boiling point than the Ate Super Blue 200. The ATE product does have one unique advantage however. The blue color makes it easy to see when the old fluid is pushed from the system. Seeing the color change through the clear bleed tube with any of the new fluids is easy on the first flush. On subsequent flushes with the other fluids this color change is more subtle and harder to detect. The Ate Super Blue is also available as ATE TYPE 200 in an amber color. The two fluids have identical characteristics other than the color. This allows you to switch between the two at each flush making it easy to tell that you have completely flushed the old fluid from the system. At about $15 a liter it is the best bang for the buck. Granted the Castrol is the ultimate, and $70 is a drop in the bucket when you look at other components and the fact that it lasts 2 years. On my personal car (77 911 with a Brembo GTP Brake system) I use and recommend the Ate Super Blue. Regardless of what fluid you choose, be sure to read the manufactures recommendations and compatibility information.


Procedure (using Power Bleeder)


1) Remove wheels and get car up on jack stands at all four corners.


2) Remove cap and sensor on fluid reservoir.


3) Use baster to remove fluid from reservoir.


4) Attach power bleeder to the fluid reservoir and pressurize it (Do not exceed 14.5 psi! I use about 10)


5)Connect drip tube to the right rear bleed valve and/or receptacle.


6) Open bleed valve with wrench and bleed till only new fluid is present in the fluid stream
(Bear in mind that if you did not fill the power bleeder with new fluid you need to keep an eye on the fluid level in the reservoir as well, insuring it does not go blow the MIN marking)


7) Close valve and then repeat on the LR, RF, LF wheels, watching the fluid level at the reservoir. (If refilling, depressurize by unscrewing the cap on the bleeder, NOT on the reservoir cap!)

That's it! You are done!

Procedure (manual method)

1) Remove wheels and get car up on jack stands at all four corners.


2) Remove cap and sensor on fluid reservoir.


3) Use baster to remove fluid from reservoir.


4) Fill reservoir with new fluid.


5)Connect drip tube to the right rear bleed valve and/or receptacle.


6) Have helper pump brakes until firm and hold pressure on them. Open bleed valve with wrench to allow enough fluid out until the pedal hits the floor. Instruct the helper to not let up the pedal until instructed to do so. Close the bleed valve and repeat until only new fluid is present in the fluid stream
(Bear in mind that if you need to keep an eye on the fluid level in the reservoir as well, insuring it does not go blow the MIN marking)


7) Close valve and then repeat on the LR, RF, LF wheels, watching the fluid level at the reservoir.

That's it! You are done!

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