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Thread: Speedster Brake Drag

  1. #1
    Speedster Member
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    Speedster Brake Drag

    Really love this car and experience of driving it (see post on General Discussion).

    Car has the Detroit Gear automatic and power brakes. During recent removal and rebuild of the engine, found that the Hydrovac had been disconnected and bypassed. (Pedal had been firm but not difficult to manage). Now that the Hydrovac has been rebuilt and reinstalled, there are occasional unexpected surges of excess boost as car comes to a stop. More alarming is a recent instance of brakes becoming hot and fading badly during 8 to 10 miles of very moderate driving. I understand that the master cylinder is a potential culprit. The anti-creep switch and valve are still in place... another possible cause? I'll have the wheel brake adjustments checked, although there's been no recent work on the linings. I strongly suspect the rebuilt Hydrovac unit, but how can I confirm this?
    Last edited by riversidevw; 06-11-2011 at 10:10 AM.
    Gil Zimmerman
    Riverside, CA

    1955 Speedster
    1956 Golden Hawk
    1958 Packard Hawk
    1958 President
    1963 Avanti R2

  2. #2
    President Member
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    Check the linkage adjustment between the brake pedal and M/C, not sure if there is an adjustment on the hy-dro-vac or not.

    Jim

  3. #3
    Speedster Member
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    There are two holes to select from, M/C rod is attached to rear hole in pedal assembly, believe that is correct for C/K bodies.

    Gil Zimmerman
    Riverside, CA

    Just realized Jim was probably referring to the adjusting screw on the rod connecting the pedal to the master cylinder. Thanks for the suggestion... adjustment seems OK, about a half inch of free travel of the brake pedal.
    Last edited by riversidevw; 06-11-2011 at 04:38 PM. Reason: My failure to carefully read text of preceding message!

  4. #4
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    Red face

    UPDATE: The brake adjustment was reportedly fine, anti-creep device said to be also in good order. The feel of over-boost when initially driving off persisted, the increasingly hard pedal with "hot" smell recurred several times. This morning I was doing a Google search on Studebaker brakes, came across Bob Johnstone's technical page on brakes, including the illustrated reference to the Hydrovac system and the related variants of brake pedals and pedal pivot points. I belatedly realized that not only had the Hydrovac been previously bypassed, but a prior owner had installed a manual system pedal. I had noticed the high brake pedal (compared to my 56J and 58L) but dismissed it (foolishly) as something related to the model year. Only other '55 I've driven much was a Commander coupe (no power brakes) fifty-something years ago. My local shop didn't notice the different pedal either, though they service a number of Studebakers.

    Guess we can't take anything for granted on a 56 year old car. The old conversion to a proper standard brake pedal explains how the Speedster could have had reasonable brake effort with an inoperative Hydrovac, doubtless it offers a lot more mechanical advantage than the pedal supplied originally with the power booster.

    Think I will just disconnect and bypass the Hydrovac (again), verify again the adjustment between the master cylinder and the pedal. I'm more convinced than ever that the power booster is the cause of the "dragging". Now that the Hydrovac is about to be out of the picture, might be a good time to switch to one of Jim's nice dual circuit master cylinder setups.
    Attached Images Attached Images
    Last edited by riversidevw; 06-11-2011 at 04:42 PM.

  5. #5
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    I have reason to update this thread after almost six years. I was dead wrong about the booster being the cause of dragging brakes. The Hydrovac was again bypassed, Jim Turner's dual circuit master was installed. As the car had been converted to the pedal setup for unboosted brakes by prior owner, disconnecting the Hydrovac was something of a relief. No more unexpected surges of overboost when braking.The car was mostly driven to local events (or Sunday breakfast) a few times a year, less than ten miles at a stretch. Each time, there was usually the aroma of hot linings about the time I arrived at my destination.

    Then came a time that the car (actually the owner) was mostly sidelined for an extended time. After a hibernation of about two years, the car started right up and drove well. (WCFB carbs are forgiving things, indeed.) But a week ago, a five mile jaunt ended with brakes pulling and that same old acrid smell. A laser-guided instant-read heat sensor confirmed what my fingers told me. The hub of the right front wheel was about thirty degrees hotter than the others... and climbing.

    An excellent local shop finally found the problem. (It had eluded the same shop before.) The front brake hoses had deteriorated. The right front hose was acting as a check valve. It didn't help that the return springs for the front brake shoes were weak. As before, the linings and cylinders seemed fine.

    Yesterday was the first time in years that the car pulled into the garage after exercising with just the pleasant, subtle aromas of a warm V8, not the acrid stench of overheated brakes.

    My earlier speculation about the Hydrovac being at fault was incorrect, perhaps misleading if left uncorrected.
    Gil Zimmerman
    Riverside, CA

    1955 Speedster
    1956 Golden Hawk
    1958 Packard Hawk
    1958 President
    1963 Avanti R2

  6. #6
    President Member RadioRoy's Avatar
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    Thanks for reporting the fix. That adds to the knowledge base. And congratulations on actually fixing it.
    RadioRoy, specializing in AM/FM conversions with auxiliary inputs for iPod/satellite/CD player. In the old car radio business since 1985.

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  7. #7
    Golden Hawk Member StudeRich's Avatar
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    Thanks again Gil for updating us. This is certainly not the first time we have heard of swelling Brake Hoses causing problems, often it is the usually neglected Two Hoses at the Hydrovac, if not the Hoses at the Wheels.

    I think I will never forget hearing the Service Manager at Frost & French, Ray Gries's voice saying: "here comes Dr. Zimmerman's Golden Hawk on the Hook again!"
    StudeRich
    Second Generation Stude Driver,
    Proud '54 Starliner Owner




  8. #8
    Golden Hawk Member
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    Installing a non-power brake pedal on C/K's with hydovacs is an excellent idea, the booster can actually be eliminated at that point, as it was never really needed in the first place!! (except on disc brake equipped Hawks, of course!)

  9. #9
    Speedster Member
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    Hydrovacs are basically useless and dangerous. The hydrovac failed on my Packard as I was backing out of the garage. There was a big puff of white smoke as the brake fluid was sucked into the engine and no brakes at all. Glad it did not happen on the freeway. The units on my 61 Hawk never worked ( 1 original, 1 nos, 1 rebuilt.) The one on my Avanti failed in So. Bend sending it into the back end of a Rambler which was unscathed however the repair on the Avanti ended up running close to $5,000. The safest thing to do is not use Hydrovac at all; leave it in place if you want it to look original. Keep the non-power brake pedal and just forget the anti-creep. The less there is to go wrong the less the risk of something going wrong KISS

  10. #10
    Silver Hawk Member bezhawk's Avatar
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    I never had a problem with them if properly maintained or if I rebuilt them. The ones I see have gone years neglected. They aren't a forget it and drive type of thing like the newer boosters, they have air filters, and must be properly lubricated to keep the leather vacuum piston sealing.The main control valve pushes on a secondary diaphragm, and it moves the vacuum valve that controls the flow to the large vacuum chamber. It is this smaller diaphragm that tears. Brake systems are supposed to be flushed every three years with DOT 3 fluid in a system. If not, then corrosion sets in because brake fluid will be saturated with water. Brake fluid sucks the water out of the humidity in the air, so it MUST be flushed, or you WILL have water in your system. This applies to every brake system ever manufactured, unless you use synthetic fluid.
    Last edited by bezhawk; 03-18-2017 at 09:19 AM.
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  11. #11
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    I would check all the wheel cylinders for s sized piston that will cause your problem.
    just finished replacing all wheel cylinders on my GT because of corrosion.
    Hawkowner

  12. #12
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    When you install a Hydovac on a non power brake car , you have to remove the check valve in the master cylinder.
    Notice that the part number for the master cylinder is different between power and non power applications.
    The only difference is the check valve. (residual valve)
    Robert Kapteyn
    http://www.studebaker-info.org/brakesystems270907.html
    Last edited by rkapteyn; 03-18-2017 at 12:32 PM.

  13. #13
    Speedster Member
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    Sure glad they work for you. As I said I have had 5 of the miserable things new and rebuilt and NONE of them worked!!

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