Dot 5 Silicon Brake Fluid

Discussion in 'Suspension, Steering, Brake & Wheel Topics' started by Desertfox63, Aug 15, 2020.

  1. Desertfox63

    Desertfox63 Member

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    Just checking to see if anyone else has had a similar situation with brake fluid and seal leaks?
    I completely replaced my complete brake system on my 1972 Camaro, and after doing a "little" research, thought that Dot 5 brake fluid would be a good choice. The reasons I believed since all of my components were new, was that if I had a leak, or while bleeding brakes, the silicon fluid is much easier on paint. One of the things I read was that Dot 5 will not harm your paint like Dot 3 or Dot 4 will. So I filled the system, bled the brakes and all seemed fine.... for 6 months. My Combination valve (brand new) developed a leak on the end seal. So, believing it may have been defective, replaced it. Now my new Combination valve is leaking again, in a different spot. I am suspecting Dot 5 fluid is maybe not compatible, and looking to flush the entire system and start over.
    Has anyone else used Dot 5, good or bad?
     
  2. xten

    xten Veteran Member

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    I've had it in one of my trucks for about 10 years. No problems.
     
  3. CorkyE

    CorkyE Veteran Member Lifetime Gold Member

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    I'm assuming by combination valve, you're saying proportioning valve? If this is an adjustable unit, try calling the manufacturer and ask about Dot 5 compatibility. I don't use Dot 5, but with everything new, you shouldn't be having this issue.
     
  4. Burd

    Burd Veteran Member Lifetime Gold Member

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    I put new lines on, had everything rebuilt, use Dot 5, it’s awesome. It’s been 20 years. No issues. Plus it doesn’t mess up your painted parts when bleeding.
     
  5. Desertfox63

    Desertfox63 Member

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    Yes proportion valve, and both new valves were from different suppliers. I am going to call next week and speak to the supplier that sold me the second unit. They are not only sales but a brake specialist. They refurbish and manufacture brake components for new as well as classic vehicles. I believe they should be able to tell me something.
     
  6. l16pilot

    l16pilot Veteran Member Lifetime Gold Member

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  7. Desertfox63

    Desertfox63 Member

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    Thanks Pilot, a very good read.
    I did call my local brake rebuilder, who sold me the valve, and as soon as I mentioned Dot 5 he told me they never recommend for any of the older restorations. He mentioned that since some seals and some of the fluids, are made in various countries around the world, they have seen a lot of issues with incompatibility. He says there are really only a couple of brands of Dot 5 on the market today that are decent enough to use, but doesn't recommend Dot 5 to any of his customers, unless the system was designed for it. He said that Dot 5 is safer on paint, and that was it's only good quality.

    So, now I am flushing the system completely, installing my new proportion valve, and refilling the system with either Dot 3 or Dot 4. I will also keep my fingers crossed that the master cylinder, calipers, and wheel cylinders will be okay.
     
  8. DrPepper

    DrPepper Veteran Member

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    IMO, if you flush the system really well, getting as much of the DOT 5 fluid out, you should be good.
    I had a similar experience w/ my Elky. And on top of using DOT 5 fluid, I used stainless steel lines. What a PITA getting all the connections to stop leaking. Probably the biggest issue was the difficulty getting the flairs correct. I'll never use SS line or DOT
    5 again.
     
  9. BonzoHansen

    BonzoHansen Administrator Lifetime Gold Member

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    The August issue of grassroots motorsports has an article on brake fluid. And reasons dot5 isn't a good choice
     
  10. nova75mike

    nova75mike Veteran Member

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    We use it widely in the forklift industry. Mostly for electric lifts. It attracts LOTS of moisture, and doesn't like to sit in brake lines without use for any period of time.
     

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