Brakes Brake fluid flush

AnthonyA1234

Active Member
Aug 17, 2020
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The brakes feel pretty mushy on my 92 gt . The car stops fine but I have to push the pedal a good amount for them to start working. Took a look at my brake fluid and it’s pretty brown. It probably hasn’t been changed in at least 5 years. Is there any harm in changing the fluid or should I go ahead and do it. Also what fluid is recommended. My car has a cobra disc brake swap 5 lug.
 

Specracer

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Nov 24, 2020
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For sure change it, zero harm to do it as much as you want (or need to if going to the track). Something I like to do, it to use a turkey baster to get as much out of the master first. Less to work through (I use a Motive power bleeder). I use race oriented fluid Motul RBF600 which is a DOT4.
 
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AeroCoupe

Founding Member
Oct 28, 2001
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Brake fluid loves water. By this I mean that once you crack a bottle open don’t leave it open. Don’t leave the lid off the MC either. Brake fluid will pull the water vapor out of the air like a fat kid on cake. Water will boil at 212 deg and brake fluid can take more than that so if the fluid in the brake lines on your car have water in them it’s in the calipers and/or cylinders and will boil creating vapor which then compresses and you get spongy brakes.

I’m down to save a buck but not on brakes so if you have an old bottle of brake fluid toss it.

For a street driven car DOT 3 is fine and check it ant least once a year for color and level. I typically flush mine every 3-4 years depending on miles.

If you road race move up to some good DOT 4 at a minimum. I regularly helped my buddy flush the brake fluid on an SCCA AI car. After four 20 minute sessions it was impressive how my buddy stopped as it was black as night. He was using Motul and it is not cheap and literally everyone in the pits was using it even the Miata guys (I’ll leave that one alone).

+1 for the Motove bleeders as they are the schniznit. Would not bleed the ABS on my Coupe without it. They make brake bleeding so much easier and it’s a one person show.

I run Valvoline brake fluid and they have a really good knowledge base here:

 
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AnthonyA1234

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Aug 17, 2020
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Brake fluid loves water. By this I mean that once you crack a bottle open don’t leave it open. Don’t leave the lid off the MC either. Brake fluid will pull the water vapor out of the air like a fat kid on cake. Water will boil at 212 deg and brake fluid can take more than that so if the fluid in the brake lines on your car have water in them it’s in the calipers and/or cylinders and will boil creating vapor which then compresses and you get spongy brakes.

I’m down to save a buck but not on brakes so if you have an old bottle of brake fluid toss it.

For a street driven car DOT 3 is fine and check it ant least once a year for color and level. I typically flush mine every 3-4 years depending on miles.

If you road race move up to some good DOT 4 at a minimum. I regularly helped my buddy flush the brake fluid on an SCCA AI car. After four 20 minute sessions it was impressive how my buddy stopped as it was black as night. He was using Motul and it is not cheap and literally everyone in the pits was using it even the Miata guys (I’ll leave that one alone).

+1 for the Motove bleeders as they are the schniznit. Would not bleed the ABS on my Coupe without it. They make brake bleeding so much easier and it’s a one person show.

I run Valvoline brake fluid and they have a really good knowledge base here:

All I can see on the internet with Valvoline is dot 3 & 4. Is this the one you’re talking about? Also can someone run down the process for flushing brakes the old school two person way? I get confused about the order in which you’re supposed to pump the brakes and all that.
 

AeroCoupe

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Oct 28, 2001
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That is the one I use but just pick a quality brand and do not mix different brands and DOT levels.

Start at the right right rear, then left rear, then right front, and finish with the left front. Supposed to start with the one furthest away from the MC and work to and end with the closest to the MC.
 
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CAMTWO1070

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Dec 17, 2021
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I flush my brake fluid everytime I do my brakes just like how I grease my zerk fittings in my frontend and driveshaft and do repack and retorque my wheel bearings plus change the dust seals also all the brake hardware like sliders shims pins and springs plus change the rubber hoses too....Heat takes its toll on spring tension need to maintain a certain tension to be properly effective against the rear wheel cylinders...

Just to be clear I drive mostly stickshift vehicles and when you do brakes 100% properly you get brakes that last aslong as they did when the car was brand new from the factory....I usually get between 50-60k miles out of my brakes and that coincides with my Z rated tires needing to be changed too with a fresh wheel alignment....LOL

Its amazing how fast brake fluid gets brown and leads to brake fade and doesnt take that long to remove the old fluid replace with new fluid and bleed the brakes....If it does means you have issues with the calipers,wheel cylinders or brakelines, brake hoses or even the proportioning valve....

Most will argue and say the brake system is a closed system and therefore it isnt recommended to do it but once every 5-10 years...

Unfortunately, your brake system doesn’t operate in a theoretical realm and moisture can make its way into the brake fluid through the hydraulic lines.

As the moisture accumulates it causes the fluid to chemically break down and the moisture begins to rust metal components in the system as a whole, you can end up with contaminated brake fluid and also causes another phenomenon called "brake fluid boil"..Getting the contaminated brake fluid out regularly keeps the brake system less contaminated and more better feeling pressure-wise..

A gallon of Dot3 and a lil time with a 1 man brake bleeder tool is cheaper than pulling dents and straightening a frame from a crash also paying a higher premium for insurance............A simple to use 1 man brake bleeder tool is $10 bux on ebay....
 
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AeroCoupe

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Oct 28, 2001
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On the Wilwoods on my cars if you rotate the knob all the way out (counter-clockwise) this is the maximum restriction which is 57%. Rotated all the way in (clockwise) is full open. The only real way to set this is where the rear tires lock up just after the front tires in a panic stop. You need to properly bed the brakes prior to doing this so they are operating at peak performance. I usually refer people to StopTech’s white paper on this.


Realize that tire compound, brake pad compound, vehicle weight & distribution, master cylinder, booster, rotor size, caliper type (number and size of pistons), and even braided soft lines all have an impact on setting up the bias. With all that each car is a little different.

Start with the valve full open and try it with four full turns counter-clockwise. From there make full turn adjustments. Once you get it where you want it go to full open again and count the turns then put it back. This way you know exactly where it is adjustment wise.

Choose wisely where you do the brake bedding procedure and valve adjustment.
 
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