Brake Fluid

Discussion in 'Dodge Challenger General Maintenance' started by SRT-Tom, Mar 8, 2023.

  1. SRT-Tom

    SRT-Tom Well-Known Member Staff Member Super Moderator Article Writer

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    Despite what the owner's manual says, it is important to flush your brake fluid every 2 years, as simple preventative maintenance. If your brake fluid is discolored (like dark tea or black coffee), you are way overdue for a brake fluid flush since there is a high percentage of water in the fluid.

    The main reason for a flush? Brake fluid is hygroscopic- it absorbs water from the atmosphere. This lowers the boiling point of the fluid and negatively affects the performance of your braking system.

    More specifically, when you brake hard or heavily, the brakes heat up. This transfers to the fluid in the caliper and the fluid where it reaches the boiling point. This can produce a mushy soft pedal, until the fluid cools back below its boiling point (see below).

    Brake fluid containing water will corrode and pit the working surfaces (piston bores in calipers) and can interfere with the seals working effectively. Another problem is corrosion in ABS pump (very fine tolerances). It is expensive to replace.

    Both DOT 3 and DOT 4 brake fluid formulas are classified by a wet and dry boiling point temperature. Dry boiling point refers to the temperature at which a fresh, unopened bottle of brake fluid would boil. Wet boiling point is based on the point at which brake fluid boils in the vehicle’s fluid lines after absorbing 3.7% water by volume. After this amount of water absorption takes place, the fluid is considered “saturated” and needs to be changed. Typically, this will take place after about two years of use for DOT 4 formulas and one year for DOT 3 formulas.

    The Department of Transportation specifies the minimum wet boiling point of DOT brake fluids after absorbing only 3.7% water content (roughly 2 years service). In the graph below, you can see that the boiling points of the various DOT fluids decline much further over longer periods of time. When brake fluid reaches 8% water content, the boiling point of DOT 3 brake fluid has been reduced almost to that of water- 100C (212 F)!

    [​IMG]
     
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  2. fritzthecat

    fritzthecat Full Access Member

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    You guys... Fuuk. :confused: I just wanna drive my car, I don't wanna be wrenchin' on it all the time. But, once again you have shamed me into some questionably necessary maintenance item. First, it was the rear diff oil. Now this. So, I figured I might as well post a how-to for anyone else who wants to try it.

    Turns out, it's not that hard. Most things aren't, if you have the right tools. First off,
    you need one of these:

    1 Mityvac.jpg

    Story: I bought this thing years ago, tried it a couple of times, and never had much luck with it. Then a couple years ago, a front caliper stuck on my '09 Sierra, and I just replaced them both (no-brainer), but bleeding the system proved to be a challenge. Now, I've always used the assistant method - little brother/girlfriend/wife/son pushing on the pedal while I open the bleeder. (See how the assistant changes throughout your life?) Well, we tried multiple times to get that truck's brakes right and the pedal just wouldn't stop being spongy. Enter the Mityvac! Hooked that thing up, squeezed and squeezed until the fluid ran clear, did the other side, and holy shit it worked! Truck is still good to this day - knock on wood! Guess it was worth buying. The other thing that I find handy is a plastic syringe like this one:

    2 Syringe.jpg
    Helps to have that long piece of plastic tube on the end, too. With this, I sucked all the old fluid out of the reservoir on the master cylinder, cuz you don't want to have to suck all of that through the brake system. It's just faster to empty the reservoir, then fill that up with new fluid before you start with the vacuum gizmo. Here's a shot of what that looks like:

    3 Master.jpg

    DON'T FORGET TO REFILL THAT RESERVOIR! Last thing you ever want to do while doing this is to suck air into the master cylinder. If that happens, you are starting over from square one. So while you're doing this, check the reservoir often and keep it topped off! After all that, you're ready to start sucking the fluid through. Start with the wheel farthest away from the master cylinder, and end with the one closest. So, right rear. Here's a shot of the Mityvac hooked up to the caliper bleed valve:

    4 Right Rear.jpg

    I fully intended to jack up the car and remove the wheel to get to the caliper. But with these wheels, ya didn't have to! How nice. With the wheel in a good position, I could easily reach the bleed valve with a wrench and get the rubber fitting over it. From there, all you need to do is pump the vacuum and wait. I recommend opening the bleed valve only about a quarter to a half of a turn. Just enough to get the fluid running and no more. I'm afraid opening it too far might let unwanted air into the caliper. It probably won't, but you don't need to, half a turn is plenty to get the fluid to run, and that's the goal. From there, it's just a forearm workout. Keep pumping until the little jar is full, then go check the master cylinder and top it off. The gauge on the pump goes from 0 to full vacuum, I keep it about half way or about 15 inches of vacuum. Keep going until the fluid starts to run clear. Tighten the bleeder valve, dump the remaining used fluid, top off the master, and switch to the left rear wheel. Pump. Fill. Repeat. Here's what my fluid looked like, from a 2010. I bought it used in 2014, but I'll bet the previous owner never changed the juice, so, yeah, 13 years old. Truthfully, I didn't think it looked all that bad. I've seen a lot worse.

    5 Fluid.jpg 6 Fluid.jpg

    Finish up with the front brakes. Turns out the bleeder valve on the front calipers is on the back side of the caliper. For these, I had to remove the wheel. But, no biggie, and it gives you plenty of room to work. Shorter run for the fronts, so a little less pumping. Don't forget - keep checking and refilling the master! Here's a shot of that set-up:

    7 Right Front.jpg

    Finish with the left front. Pretty straightforward, and not too difficult. Finished up, put everything back together, noticed that the first time I started and moved the car, the brake pedal went all the way to the floor, so my advice would be, first time you start the car, don't try to move it immediately. Wait a few seconds, sloooowly push the brake pedal to the floor, sloooowly let it up. Do that a couple of times until it feels right, then put the car is gear. Mine pumped up after a couple of presses, and it has been good ever since. I don't like to vigorously pump a brake pedal, because I'm afraid that may sometimes introduce air into the system, and ya never want that. Slow and careful works well.

    My car has the Brembos and the aluminum Alcoa wheels. Yours may be a little different, but the theory is the same. You may end up having to remove the rear wheels. The bleeders may be in a little different place, but they are always at the top of the caliper.

    Good luck! Hope this helps. Let us know your experiences. :hands:
     
  3. george galvin

    george galvin Active Member

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    Nice, Im doing that now as in Today. I read your post and yes it looks straight forward. Thanks for da pointers...
    Oh a what type fluid did you use, dot3 r dot4?
    Also Im changing the brake lines, they're rubber and Im told they soften up over the years. The guy who owned the car since new changed the oil and kept the thing spotless, (Thanks Guy) but that was the only maintenance he did so far as I can tell, so rotors, pads and brake lines plus the flush.
    I went with 4 for its higher boiling point, more expensive too but. I live outside of Sac and it gets HOT in the summer, plus someday I hope to go to an open track day and see how she and I do.... BIG FUN
    Thanks
     
  4. Moparisto

    Moparisto Full Access Member

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    Drat it all, I recall a race driver who died from NOT pumping his brakes after a pad change and running right into a wall at high speed, and his father had ALSO died in a brake-related failure in HIS race car. I saw it in a print book, I believe it was The Speed Merchants, but, good luck trying to find content like that in the "we only show what we get paid to show" days of the internet and it's carefully-policed Woke search engines that orbit around profit.
     
    Last edited: Mar 17, 2024
  5. Sexy Blue

    Sexy Blue Active Member

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  6. fritzthecat

    fritzthecat Full Access Member

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    Interesting. So, that being a pressure bleeder, I guess you put it on the master cylinder reservoir and push the fluid through the system? Open one bleeder at a time? The same caveat applies - make sure you keep the reservoir filled, you never want to get air in the system. Let us know how it goes when you do the job!
     
  7. Sexy Blue

    Sexy Blue Active Member

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    You can add as much as you want to the pump up bleeder, but same drill, check after each wheel. I usually suck out the old in the master, fill it up with fresh, and attach the pressure bleeder.

    I use this to test all my vehicles. The ones I park inside fare better, I think my car was parked outside for quite a while on the dealer lots.

    https://www.amazon.com/dp/B076SC377...-iyBTu5FWgJfYP3z8iVsLXWN1T0d5XdS4gG6yEBQurrwj
     
  8. Octane

    Octane Full Access Member

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    I have a fluid test meter to determine moisture content.My fluid after 4 years is less than 2%.Speaking of my truck.Which is fine.