No announcement yet.

Golden Hawk Brakes

  • Filter
  • Time
  • Show
Clear All
new posts

  • Golden Hawk Brakes

    The car had sat with silicone fluid for 25years it had a very spongy pedal and not wanting to cut corners with brakes I bought an overhaul kit (new master cylinder, wheel cylinders,springs,hoses etc). I pumped a couple of litres of alcohol though the old system until clean alcohol came through followed by compressed air.
    I installed all new parts and used dot 3 fluid (largely because dot 5 wasn't easy to come by in Australia, although I found it afterwards), even though the car is up on stands the brakes felt good and a nice solid pedal feel.
    A week or so later I was under the dash connecting a wiper motor I lent against the pedal and it went to the floor, I checked for leaks and found none but tightened up all the connections and re bled the brakes however in a little over a week the fluid had gone from bright blue to almost black. I pulled the master cylinder again and took it apart there were very tiny metal shards in the bore but the seals looked visibly good (although the check valve looks upside down on the spring compared to the illustration in the shop manual).
    After speaking with SI (where I bought the parts) it was suggested that trace amounts of dot 5 have mixed with the dot 3 to cause a chemical reaction weakening the seals, can anybody suggest what may have happened or measures to fix it ?

  • #2
    Does the car have power brakes, or a hill holder? Did you replace the stop switch? (these areas will 'hold' dot 5 if not completely taken apart. And lastly, did you flush the lines with brake clean?

    Flushing with alcohol cleans the lines of Dot 3. Alcohol will not 'clean' Dot 5 all the way because it is silicone based. I hate to say it but I think you have to start over, cleaning Dot 5 is not easy and maybe take a few things apart and clean some more. Use brake clean.

    Did you use your original master cylinder cap? The shards you see are from the new threads cutting into it. Use the plastic cap that came with it.
    Last edited by (S); 11-13-2010, 12:34 PM.


    • #3
      It doesn't have power brakes nor a hill holder. I didn't take the stop light switch out, what you said sounds logical as when I pulled the old master cylinder apart there was a gel like build up on the spring which I guess is from the alcohol and silicone mixing. Also I used the cap that came with the master cylinder (but I do have a plastic cap that's off a really old worn out cylinder I can use).
      Do you think all wheel cylinders and master cylinders will have to be rebuilt and the rubber hoses swapped out again ?


      • #4
        FWIW, DOT5/silicone fluid is basically inert. I've never had any problem with trace amounts of silicone fluide contaminating DOT3 or DOT4 brake fluids.

        Conversely, any of the DOT3 or 4 fluids when mixed in with silicone will absorb moisture and settle to the bottom of cylinders and reservoirs.

        BTW, what kind of made-in-OZ DOT3 fluid is bright blue?

        jack vines


        • #5
          Thanks for the info,
          It's "Valvoline super heavy duty dot 3"