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gthawk brake question

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  • Brakes: gthawk brake question

    My gthawk had been sitting for an extended period and I wanted to do a coolant flush. When I first started it up , the brake pedal seemed fine, but then upon placing pressure on it again, the pedal sunk to the floor. In order to move it, I had to pump the pedal twice upon which the second pump seemed to have some pedal. But once I took my foot off it, the next time the same thing happened.
    I decided to pull the booster from the bracket and do the neatsfoot oil thing, let it soak overnight. No real improvement. I figured the master was bad or the seal blew, so I ordered a new master. Got under the car, cleaned everything up, added fluid to the remote reservoir, which was almost empty. Pumped the pedal to see If I could tell where it was leaking. No leak around the master cylinder. No leaking around the calipers or wheel cylinders. Can't figure where the heck the fluid when because I knew the reservoir was much more full when I left it. Started the car, still a bad pedal.
    I decided to bleed the hydrovac unit. Rechecked the pedal and it was good. Started the car, pumped the pedal like 25 times. Firm as can be. Shut the car off and the pedal did the mild sink as it shut down, but stayed firm...indicating good hydrovac. Got under the car. rechecked all the lines and the master, no leak. Got in and rechecked the pedal another 15 -20 times, still firm. Shut the car, started it up, still a great pedal. I plan to rebleed the calipers and wheel cylinders, but here's my questions.
    Am I out of the woods on this. is it safe or will I be driving and the brakes fail wiping out my front end. All appears well. Or, should I change the master anyway to play it safe. Sometimes things are best left along. Thoughts?

  • #2
    Always a safe bet to replace ALL of the brake components on a car that’s been sitting for an “extended period”. If one part failed, the other parts aren’t far behind.

    Out of habit, the first thing I do on any Studebaker I buy is a full brake job, even if the car is already a driver. It’s cheap peace of mind.


    • #3
      What is an 'extended period'?


      • #4
        Last ran about a year ago.


        • #5
          Originally posted by Bruce S View Post
          Last ran about a year ago.
          If 'last ran' means it was fully operational and on the road fairly regularly, I'd just top up the fluid and drive on. If it means the motor was started, and it was 'yard driven', and it has actually not traveled 100 miles in years or decades (as is the case with most Studes), I'd follow Matt's advice, totally disassemble, inspect, and replace all rubber components, at a minimum.


          • #6
            Click image for larger version

Name:	R (1).jpg
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ID:	1903559 There is a second "master cylinder" inside the hydrovac. Essentially the hydrovac is a boosted master cylinder, and the function of the one under the floor is to control the booster. It is a flow through system so if it goes out the one under the floor will still provide some braking pressure. My guess is the booster is leaking internally, and sucking the fluid through the vacuum connection to the engine. That is why you can't find the leak.
            Last edited by bezhawk; 07-17-2021, 07:43 AM.
            Bez Auto Alchemy

            "Don't believe every internet quote" Abe Lincoln


            • #7
              The first pedal is low, then the second time is high. Taking foot of brake a few seconds and it repeats. So, if that's the case and it indicates the booster, where do you recommend I get one or have mine rebuilt. Thank you.


              • #8
                I contacted this guy. He said it may to be the booster, Rather than try to sell me on rebuilding, he thinks it is air in the system. He said there should be two bleeders on the booster. I only see one, so I sent him some pics. He mentioned that he rebuilds these for some of the studebaker suppliers? So, it might be a good lead. Seems friendly enough. I will post what he says. Here's the info below;

                "Thank You for the website/email inquiry.

                YES we would be happy to rebuild YOUR 1963 Studebaker GT Hawk booster.

                We estimate the cost to be $345.00 (US) (plus shipping and a $20 shop fee per order) for the rebuild.
                Due to the pandemic we are extremely behind and the turn around time currently would be around 2-3 weeks in house once we receive your booster.
                We do NOT offer exchange units, we would rebuild YOUR unit.

                Additional charges may be incurred to replace broken or missing parts.
                Please note there is an additional charge of $50.00 if your unit has been disassembled.

                Please ship your order to: (we suggest you use tracking)
                Brake Materials & Parts Inc
                800 Sherman Blvd
                Fort Wayne IN 46808

                Include the attached form or a note with your name and contact information and the year, make and model.
                Please include any specifications or additional instructions if needed.
                IMPORTANT: place your paperwork in a sealed plastic bag for protection from fluid and damage.

                If convenient please send us an email to let us know you have shipped your order and with which carrier.
                This will place it on our rebuild schedule and we will notify you when the shipment is received.

                We will call you for a credit card when your order is completed.
                Please DO NOT include this information via email for security purposes.

                We will return the order via UPS (or Best Way) to the address you request.
                If you have additional questions or need additional information please don’t hesitate to phone.

                THANK YOU for the opportunity to help with your braking needs.
                Please let us know if you need assistance with additional brake parts.
                We offer everything in brakes and will do our best to STOP everything for you."

                Respectfully Your Brake Experts,

                Scott & Margaret Bethke
                Brake Materials & Parts Inc
                800 Sherman Blvd
                Fort Wayne IN 46808

                Phone: 260-426-3331 or Fax: 260-424-1331


                • #9
                  The brake booster on Hawks with disc brakes has only 1 bleeder screw. Those without disc brakes have 2.
                  Biggest difference between the two is the disc brake unit has higher line pressure.