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Lets start a fight- Brake Fluid

Discussion in 'Early CJ5 and CJ6 Tech' started by Howard Eisenhauer, Feb 16, 2014.

  1. Feb 16, 2014
    Howard Eisenhauer

    Howard Eisenhauer Administrator Staff Member

    Tantallon, Nova...
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    It will soon be time for me to charge up Tonk's brake system; all new components- stock 11" brake cylinders, Willwood aluminum dual MC, fancy-shmantzy modern internally copper plated lines. Never had any fluid of any description in it anywhere.

    So, which brake fluid should Ii use/ DoT3, DoT4, DoT5, DoT5.1, used motor oil, salt water, old deep fryer drippings?

    Enquiring Minds want To Know...

    H.
     
  2. Feb 16, 2014
    sawilly

    sawilly Member

    Salmon Arm BC
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    From my personal experience I have used DOT 5 just because it not hydroscopic like Dot 3 is . Silicon based. I have wheeled through water and actually had water in my brake system using the DOT 5 .After cleaning it out I had no corrosion issues like DOT 3 did . So I use DOT 5 with good luck . I also find that the DOT 5 also has a little less lubrication to it.
    I used DOT 3 in my cj2A and under the same conditions it had corrosion isssues.ie Stuck wheel cylinders .

    just my 2 cents
     
    Last edited: Feb 16, 2014
  3. Feb 16, 2014
    1960willyscj5

    1960willyscj5 Well-Known Member

    Mesa, Arizona
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    What did Willwood recommend?

    On the other hand you are using stock wheel cylinders. With stock internals? You probably want to go with Dot 3 because that was what was available when those were first built, right?
     
  4. Feb 16, 2014
    ojgrsoi

    ojgrsoi Retired 2024 Sponsor 2023 Sponsor 2022 Sponsor

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    No particular reason but I would choose DOT 5 with all new components.
     
  5. Feb 16, 2014
    Wenaha

    Wenaha Member

    West Coast
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    I am about to install a new dual MC, SS lines, and new wheel cylinders in my 2A. It has 11" X 2" brakes from a mid-70s CJ5. I am interested to see what brake fluid everyone recommends.
     
  6. Feb 16, 2014
    Howard Eisenhauer

    Howard Eisenhauer Administrator Staff Member

    Tantallon, Nova...
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    Willwood does not recommend 5 for racing due to it becoming more compressible at the higher temps generated by heavy braking during racing which apparently reduces pedal feel & consequently braking control. They recommend special racing formulations of DoT 3 or 4 for that however from other things I've read the racing fluid is not recommended for long term "road" use as it's more water absorbent than regular DoT 3/4. Otherwise they don't seem to have a preference & in fact have their own brand of regular DoT 4 & DoT5 fluids.

    As for the wheel cylinders / DoT3 thing I really don't see a reason why you would limit yourself to DoT3 because of stock parts, the only possible issue appears to be comparability with the seals & for that the only issues I can find are related to DoT5 fluid- DoT 3/4 appear to be completely interchangeable. DoT 5 seal problems appear to be:

    -The first Dot5 formulations made in the mid 70's (yellow colour) did have issues with swelling seals, the later stuff is not "supposed" to be an issue with anything rubbery used in brakes except for-.

    -The current formulation (the purple stuff) of DoT5 has been (internet) rumoured to have issues with some older (pre 70"s) rubber seals used in british/european seals (Porsche gets mentioned a lot, but apparently VW's aren't an issue :rofl: ) .


    Actually researching this on the net has been a real education :) The whole thing is a classic example of (miss?) information being re-posted time after time, usually verbatim, as gospel by people with no first hand experience in what they're talking about. To wit:

    Racers don't use DoT5 because it's worse.
    Racers use DoT5 because it's better.
    You can mix DoT5 with other stuff without issue because they won't actually mix at all.
    You can't mix DoT5 & other stuff because they will combine & turn to jelly.
    DoT5 is better because it won't absorb water so your brake system won't corrode.
    Dot5 is worse because it won't absorb water therefore the water pools in low spots so your brake system will corrode.
    Dot5 is sqiuishier than others because it's a silicone fluid & that's it's nature.
    Dot5 is squishier than DoT3/4 because it absorbs air in the spaces between the silicone molecules.
    The air will come out from between the DoT5 silicone molecules & form bubbles making the brakes squishier.
    The air won't come out from between the Dot5 silicone molecules & form bubbles making the brakes squishier.
    Dot 5 reduces braking pressure because it's squishier.
    DoT5 reduces braking pressure because as it heats up it gets even squishier than normal.
    Dot5 will result in your pedal being noticeably softer.
    Dot5 will make your pedal go closer to the floor for the same braking effect
    There's no noticeable different in braking between DoT 5 & DoT 3/4.
    Dot5 will make your system fail earlier because it doesn't lubricate as well as DoT3/4
    Dot5 will make your brake system last longer because it lubricates better than DoT3/4

    Like I said, a real education :)

    H.
     
    Last edited: Feb 16, 2014
    Rick Whitson likes this.
  7. Feb 16, 2014
    PeteL

    PeteL If it wasn't for physics, and law enforcement... 2024 Sponsor 2023 Sponsor 2022 Sponsor

    Hills of NH
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    An education indeed, just as you say. Your summary is excellent, and just the same as I have found.
    People have strong opinions. My conclusion is that each type has it's particular pros and cons.

    Personally I have used DOT#5 for 20 and more years in particular antique vehicles with no evident brake problems at all. I am sure that DOT#3 would have attracted corrosion.

    But the relative advantages may depend upon your maintenance schedule (flushing) etc.
     
    Last edited: Feb 16, 2014
  8. Feb 16, 2014
    Twin2

    Twin2 not him 2024 Sponsor 2023 Sponsor 2022 Sponsor

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    for aluminum . I would use Dot 5 . just because that's what you use on motorcycles .
     
  9. Feb 16, 2014
    Howard Eisenhauer

    Howard Eisenhauer Administrator Staff Member

    Tantallon, Nova...
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    According to the internet only Harleys's use DoT5- European/Japanese BSO's use DoT3/4 unless they say DoT5 on the MC cover, but they don't actually mean DoT5- they actually mean DoT5.1 which isn't the same thing at all as DoT5 but really DoT3/4 only better.


    Maybe.

    H.
     
  10. Feb 16, 2014
    Middlefork Miner

    Middlefork Miner Member

    N. Highlands Ca
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    1 vote for DOT 3...
    Not brake related....but...I was up in the hills camping in my 66' Ford van back in the mid 70's & I tore a transmission cooling line off...:rofl: I used water to get back home.
     
  11. Feb 16, 2014
    cj6/442

    cj6/442 Sponsor

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    my Jamar line lock paper work says anything other than Dot5.
     
  12. Feb 16, 2014
    Howard Eisenhauer

    Howard Eisenhauer Administrator Staff Member

    Tantallon, Nova...
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    I'll bite- Why?

    H.
     
  13. Feb 16, 2014
    Keys5a

    Keys5a Sponsor

    Florida Keys
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    Everyone has a favorite brake fluid, just like engine oil. My favorite is DOT4, specifically ATE super blue, and amber. I like these two identical fluids (other than color) because when I flush the brake system every couple years, I can see when the old color is flushed out. I use this stuff in all my vehicles including classic British and modern German cars.
    I will not ever use DOT5 silicone again. I used this stuff years ago, and found out the hard way it doesn't work in my climate. In high humidity, it doesn't absorb moisture, but the brake system still vents to the environment, so moisture enters the system and forms water drops that find their way to the lowest points of the system and sit there. Rust and/or corrosion pits wheel cylinders in just a spot, ruining them and causing leaks.
    If you live in a very dry climate, this may not be an issue, but in deep south, it certainly is. At least with DOT 3 or 4, the moisture absorbs into the fluid and doesn't concentrate anywhere causing rust to form. Moisture in the fluid lowers the boiling point, but in most (non-racing) vehicles doesn't affect normal performance much, and thats why we are supposed to flush the system every couple years.
    -Donny
     
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  14. Feb 18, 2014
    nickmil

    nickmil In mothballs.

    Happy Valley, OR
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    DOT 5 has an advantage as stated above about not being hygroscopic. I don't use DOT 5 unless specifically stated to use it or on vehicles that will sit without being driven for very long times because if turbulence is encountered it can form air bubbles much easier than other brake fluids. This can make it a real pain to bleed the system or if the brakes are used violently air bubbles can form pretty easily in the system leading to a soft pedal.
    We tried DOT 5 in our race cars. It was great for temperature resistance but under aggressive driving the above would happen and we would have braking issues. Went back to DOT 4 and problem solved.

    Just what I've experienced. As usual, YMMV.
     
  15. Feb 18, 2014
    windyhill

    windyhill Sponsor

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    Dot3...use dot4 in VW...never had a problem...usually flush out every few years. It's cheap.
     
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  16. Feb 18, 2014
    oldtime

    oldtime oldtime

    St. Charles,...
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    As some of you know my daily driver is a a stock optional CJ-3B.
    It's all rebuilt original and/or NOS OEM parts.

    The brake tubes all happen to be original.
    They were removed and cleaned out internally using alcohol and pipe cleaners attached to a piano wire.
    The Wagner wheel cylinders are all NOS from Kaiser.
    The old stock Wagner master cylinder was previously used with Dot 3 in it.
    It was cleaned, flushed, inspected then installed without a rebuild kit.
    I've had Dot 5 in this system for over 3 years now with zero problems to date.

    The Dot 5 fluid also makes a good wiping agent for the front axle hemisheres.
    I soak the new hemisphere felt wipers with Dot 5 fluid.

    At worst I'd say that the Dot 5 system was only slightly harder to bleed than Dot 3.
     
    Last edited: Feb 18, 2014
  17. Feb 18, 2014
    Howard Eisenhauer

    Howard Eisenhauer Administrator Staff Member

    Tantallon, Nova...
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    For those of you who have experienced issues with Dot5 & water, are you still running a stock MC vented to the atmosphere or something with a diaphragm in it?

    Re. the DoT5 air thing I have my doubts about the long term efficacy of this but I'll post it up for the "neat' factor if nothing else :)-

    http://www.youtube.com/watch?v=a9IWde0n0Cg


    H.
     
  18. Feb 18, 2014
    Posimoto

    Posimoto Hopeless JEEP Addict

    Minden, Nevada
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    I tried Dot 5 in my hydraulic clutch and switched back to 4 after experiencing a flat pedal on a difficult trail. It may have been the aeration that Nick mentioned above. I bled the system on the trail and made it out OK, but got rid of the Dot 5 and have never had a problem with the clutch since then.
     
  19. Feb 18, 2014
    PeteL

    PeteL If it wasn't for physics, and law enforcement... 2024 Sponsor 2023 Sponsor 2022 Sponsor

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    I really have a hard time imagining how aeration could happen to that extent. If it were possible, how could Harley-Davidson trust DOT 5, and the US Military?
     
  20. Feb 18, 2014
    nickmil

    nickmil In mothballs.

    Happy Valley, OR
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    This is why most manufacturers of vehicles with abs recommend DOT 3 or DOT 4 and recommend against DOT 5 silicone based fluid. Believe or not as you like, but we've had it happen.
    The military and Harley Davidson is looking at storage issues with hygroscopic fluid they know they will have vs. other issues they may have.
    Another advantage of DOT 5 is it tends not to eat paint like DOT 3/4 does and to the best of my knowledge DOT 5 is not flammable unlike DOT 3/4. These are other considerations they must take into account.
    Life is full of decisions like that.


    Sent from my iPhone
     
    Last edited: Feb 18, 2014
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