Where is my Brake fluid going?

I've got a 54 Hudson Hornet with a BTV master cylinder. The 4 rubber brake lines along with all the brake cylinders and brakes were replaced. The car now stops on a dime and with the new shocks it is a delight to drive.

My problem is that I seem to be losing brake fluid in the BTV as I need to add fluid every time I take it out for a drive. I find no leaks, but someone suggested that it might be going directly to the motor via the vacuum hose. The vacuum hose goes to a black reservoir tank and then to the engine. I tap the tank and it sounds hollow so I don't think I'm collecting brake fluid into it, but I'm not sure how the inside of that tank is set up. Any suggestions how to find out if my brake fluid is actually passing into this vacuum line and into the motor?  Thanks


  • onerare39
    onerare39 Expert Adviser, Member
    edited May 2022
    There are a couple of things you can do.  Disconnect one of the hoses at the tank, the front one is probably the easiest.  Then tape a small piece of paper or a Q-Tip onto a piece of wire and insert it onto the tank feeding it in so it touches the bottom of the tank.  Pull it out and see if it is saturated with brake fluid.  Don't leave it in too long as the brake fluid may deteriorate the adhesive on the tape.  You can also remove the hoses from the tank and remove the tank from the inner fender, turn it on end to see if fluid runs out.  If you are using DOT-3 brake fluid be careful, it will damage painted surfaces. The tank is hollow inside.

    Hope this helps.
  • 50C8DAN
    50C8DAN Senior Contributor
    If you are losing that much brake fluid it should be apparent on the inside of all the vacuum hoses from the MC to the VC and beyond.  I had a problem with my Hydrovac on my Studebaker and I could pour out fluid from the vacuum hose.  
  • lostmind
    lostmind Expert Adviser
    edited May 2022
    It could be sucked into the intake and burned. 
    Did you try driving with the vacuum hose disconnected and plugged?
  • lostmind said:
    It could be sucked into the intake and burned. 
    Did you try driving with the vacuum hose disconnected and plugged?
    If I disconnected the BTV vacuum hose and plugged it.... would that negatively affect the braking ability of the car? 

  • onerare39, John.  Thank you for that suggestion. I will take the tank off and do as you suggest.
  • StepUp
    StepUp Member
    Curious whether you found the source of the leak? I have the same braking system on my '54 Super Wasp.
  • I pulled the reservoir tank off the inner fender and it had about 5 ounces of brake fluid in it. I will need to purchase a refurbished unit as I'm not competent to rebuild it myself. Thanks for all your replies.