74' Pedal Box Project, Part 2

Discussion in 'Workshop Forum' started by Rupunzell, Oct 6, 2014.

  1. Rupunzell

    Rupunzell Bernice Loui

    Location:
    California
    Pedal box plumbing done, hoses attached, next step is to fill up the cylinders and persuade as much air that was in the hoses, tubing and cylinders out replacing air with fluid.

    Two 60cc syringes are use to fill the pedal box system with DOT 4 brake fluid and a test fitting with a brake fluid catch bag on the end of a hose is attached to the test fitting. Once the initial brake fluid fill has been done. The syringe plungers are removed and mount high above the pedal box assembly, pedal box assembly rotated, hoses tapped, repositioned to persuade as much air out of the system as possible. Putting more fluid into the system alone will not get the air out. It is a matter of using gravity and difference of density between air -vs- fluid to move the trapped air out of the system. Both clutch and brake master cylinders are subjected to this procedure to remove as much air as possible.


    [​IMG]


    Once the trapped air has been purged enough, pressure test gauges are attached to the pedal box test fittings. Air purge continues with these test gauges in place. Air purged from the test set up, front and rear brake master cylinders are tested for pressure balance. If all is well, both tandem master cylinders will produce the same amount of pressure for a given pedal force. If there is any difference in brake fluid pressure, it must be corrected before installing the pedal box assembly into the exxe.

    [​IMG]

    This same procedure is applied to the clutch master cylinder to test and verify it is operating properly and the system is leak free.

    [​IMG]

    Here is a bottom view of the pedal box. At this point, set the pedal free play stops for both pedals to engage the cylinders on the same plane. This could be further adjusted in car as needed.

    [​IMG]

    View of the brake master cylinder side of the pedal box.

    [​IMG]


    When the pedal box system has been tested for proper pressure capability, no leaks, as air free as possible. The test fittings and brake fluid feed hoses are capped to seal off both ends of the cylinders. This traps brake fluid in the system and readies it for installation.


    The 60cc syringe with brake fluid is applied to the brake lines in the exxe, air bleed fittings opened with the brake fluid collection bag and hose attached to the bleed fitting on the clutch slave cylinder. Once air free brake fluid is observed at the clutch slave bleed fitting via the collection hose & bag, the fluid flow from the syringe is stopped, bleeder fitting closed off and syringe removed.

    This same procedure is applied to the front and rear brake lines to purge as much air out of the open lines as possible before installing the pedal box assembly.

    [​IMG]

    Pedal box assembly installed, lines connected, and the system mostly works good. Only minor air purging from the system is required to finish up. If the brake fluid feed lines remain sealed as the tube connections are being made in the exxe, little if any brake fluid will escape from the filled pedal box assembly. Once the tubing connections are in place and tightened to spec (apply a bit of anti-sieze to the tube nuts as those who do work on these tube nuts will thank you later), remove the cap on the feed lines to connect the fluid reservoirs, mount them and fill them with brake fluid.

    [​IMG]


    Curious difference with the 74', there is a brake line pressure differential switch (Replace with a block union on later years) that is wired to the brake indicator light on the instrument panel. This pressure differential switch has 45 degree SAE double flares on 3/16" steel tubing with 3/8" x 24 tpi tube nuts on the exxe's tube end. These had to be cut off and replaced with M10 x 1.25 long tube nuts with bubble flares to make the in car brake line compatible with the later version of this pedal box assembly.


    The left hand brake line is not compatible with the JIC/AN -3 Tee fitting on the end of the Wilwood pressure limiter. A replacement brake line with a M10 x 1.25 long tube nut and bubble flare on one end and JIC/AN-3 B-nut and sleeve was made and installed.

    [​IMG]

    Once all is in place, one more round of air purge of the entire system assembled in the car will finish it up.


    Image of the Wilwood pressure limiter and new brake line.

    [​IMG]


    Image of the brake pedal side of the installed pedal box.

    [​IMG]


    Pedal box install complete, air purged, pedal heigh set, time to take a test drive. It all worked out well. Pedals are far smoother than before, pedal feel is now direct with near zero slop and proper pedal height relative to the throttle pedal. It is worth noting that the pedals are properly set up for toe-heel on the exxe. When all is correct as it was originally designed, the pedal position is very good for performance driving.

    Brake fluid reservoirs with their caps off:
    [​IMG]

    Closer view of the brake fluid reservoirs. All new hoses and they are marked with color shrink tube to ID front, rear brake. New SST injection clamps on the hoses and all new hardware. One of the M6 mounting studs snapped off. The M6 stud was drilled# 20 then tapped to 10-32 internal thread. A 10-32 screw applied with a special spacer to allow the stub of that OE M6 stud to center on the OE mounting bracket. This is just visible at the far corner near the base of the windshield.
    [​IMG]

    Rotated view, Brake reservoirs are ID using color tape.
    [​IMG]

    Reservoirs with the caps on;
    [​IMG]


    Here are a few images of the pedal box that came out of the 74'. Mostly all original with years of dirt and ick accumulated from all those years.

    [​IMG]


    The brake master cylinder and plastic bushing stop. The brake pedal bushing had rusted solid on to the plastic bushing causing the plastic bushing to rotate against the stop. This is a very common problem in the exxe. It is caused by lack of lubrication and dripping brake fluid and other fluids on to the pedals and plastic bushing.

    [​IMG]


    The other problem area, worn push rods and pins on the pedals. This one is not good at all.

    [​IMG]


    Last, this is the M12 x 1.25 tube nut used on the clutch master cylinder. It was so rounded off that the vise-grip treatment with PB blaster was applied to remove it.

    [​IMG]



    :)
    Bernice
     
    Last edited: Oct 6, 2014
    Stoney#1 likes this.
  2. kmead

    kmead Over half way.

    Location:
    Michigan
    Great job (obviously). Makes me worried about exhuming mine when the time comes.

    As I don't recall from past passages, was there anything special about the paint used on the assembly? Are there paints available to normal people that would be more resistant to the deleterious effects of brake fluid?

    Thank you for documenting this process so completely, it gives a great target to aspire to!

    Karl
     
  3. PaulD

    PaulD Paul Davock

    Location:
    Kitchener, Ontario
  4. Rupunzell

    Rupunzell Bernice Loui

    Location:
    California
    OE is plain paint which dies a slow death due to leaking brake fluid and more. This pedal box was blast cleaned due to surface rust (very, common) then prepped for primer with Zinc Phosphate the same stuff used on aircraft which is dark green. Then painted with enamel. It is very modestly brake fluid tolerant.

    If the rust and corrosion was not so bad, plating the who assembly with electroless nickel would be nice. The pitting from rust and corrosion prevents the electroless nickel from adhering properly which leaves semi-plated pits that trap moisture that results in rust under the plating surface.

    A good alternative would be powder coating with proper prep work.


    Bernice



     
  5. bbrown

    bbrown Bob Brown Moderator

    Location:
    New Hampshire
    Brake fluid is brutal to nearly all paint

    Even powder coated surfaces. For short times, (like hours) powder coated surfaces can survive pretty well. Overnight will show a surface breakdown of the powder coating.
    But for polyurethane, that time gets much shorter.
    Acrylic paints hold up "a little better" than polyurethane.
    Krylon - forget it. Might as well be a solvent.

    BTW, I'm a believer in using Zinc Phosphate under all my topcoats.
    It's amazing what even a thin layer of that stuff does to resist rust.
    (a thicker layer also helps hide minor pitting)
     
  6. lookforjoe

    lookforjoe True Classic

    Nice documentation of a very professional job!

    I for one appreciate all the detailed pics and coverage of failure points. Makes it easier to evaluate what's in my X. With almost 130k and 28 years gone by, it's just a matter of time..
     
  7. Black-Tooth

    Black-Tooth Tony Natoli

    Hey Bob... what about PowDER-Coated Finishes?

    "... Even power coated surfaces. For short times, (like hours) power coated surfaces can survive pretty well."

    Just how much POWER is required for these finishes... like 105 psi or something? Do I need to buy a more powerful compressor or just PUSH HARDER with a brush?

    Considering all that, I imagine HVLP sprayed-on finishes would be a dismal failure at resisting damage then, huh...
     
    Stoney#1 likes this.
  8. bbrown

    bbrown Bob Brown Moderator

    Location:
    New Hampshire
    Yeah, I got it...

    Looks like my D key is getting the best of me. :nana:
     
  9. Gamecock

    Gamecock Rusty 74

    Location:
    Columbia,SC
    Looks Familiar

    Bernice,
    Excellent work!
    Your peddle assembly looks very similar to the one I took out of my 74. It is sitting in a tray waiting for its turn. I am currently cutting out metal and fitting replacement pieces around the windshield.
    I will be referring to your info for my re-work.
    Thanks for sharing the info.
     
  10. MikeHynes

    MikeHynes True Classic

    Location:
    Goodfield, IL.
    Epoxy Primer holds up to brake fluid.

    It's commonly available in Black or Grey.
     
  11. bbrown

    bbrown Bob Brown Moderator

    Location:
    New Hampshire
    Not for long...

    Epoxy will eventually soften and break down. At least in my findings.
    I've also tried powder coat too. Bubbles when it breaks down.
     
  12. mikemo90

    mikemo90 True Classic

    Location:
    rodeo,ca.
    tool

    could you post a pic of the tool you used to remove the clutch spring?? I think it's the only fiat factory tool I don't own.
    and if anybody wants if they send me parts sandblasted clean, and the powder color of their choice(I use eastwood) I will powdercoat them for free, but I keep the leftover powder for the next job they need done
    mikemo90*aol.com
     
  13. Black-Tooth

    Black-Tooth Tony Natoli

    Hey Mike... I know of ONE tool to get the springs off...

    which is similar to the same tool to get the springs on.

    That would be... a roll of quarters or nickels... and don't expand on this with any of your two-bit jokes... (Double pun intended!)
     
  14. ianlawson

    ianlawson ian - NZ

    Superb explanatory write-up there, Bernice!! :)

    cheers, IanL - NZ
     

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