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Diaphragm Bleeder Maintenance – Sprint Cars

Diaphragm Bleeder Maintenance – Sprint Cars

Bleeders are essential for consistent tire pressure management during a race. They operate on the same principle as a high-speed bypass valve—preset spring pressure acts against a diaphragm, controlling how much air is released. These bleeders release air instantly in a 360-degree pattern and are accurate within 0.2 PSI. With four different springs available, they cover a pressure range of 2 to 30 PSI.

🧰 Installation Instructions

  1. Start Assembly in This Order:
    • Insert the fiber washer first.
    • Drop the poppit washer (bevel side up) in the center.
    • Place the diaphragm in with the small impression circle facing up.

      Tip: The diaphragm may not lay flat—use the spring from underneath to gently push it into position. It will self-center.

  2. Assemble the Bleeder Body:
    • Hold the main body in one hand and thread the back piece into place.
    • Slowly rotate the bottom piece until it bottoms out.
    • Tighten the back piece using a #10 line wrench (1”)—do not overtighten.
  3. Connect the Nylon Hose:
    • Insert the hose up through the hole opposite the muffler.
    • Slide the spring onto the hose.
    • Leave about 3/16” of hose exposed, then push it into the orange donut inlet.
    • Slide the spring down to the orange donut and pull the excess hose outward until the spring fits snugly.
  4. Inspect the O-Ring:
    • Check the O-ring on the plastic piece that enters the wheel.
    • If it’s cut or grooved, replace it—it’s a common leak point.
    • Spray with soapy water or Windex and check for bubbles to confirm leaks.

⚙️ Setting Bleeder Pressure

Use a regulated air tank (preferred) or a tire to set bleeder pressure:

Using an Air Tank (Best Method):

  1. Put ~10 PSI into the tank.
  2. Slowly loosen the end cap—you'll hear the bleeder begin to vibrate.
  3. As you near the desired pressure, bring the lock ring up to the end cap.
  4. Tap the bleeder against the tank or table while watching the gauge.

    Tapping simulates the vibration it would experience on the track.

  5. Fine-tune the pressure and then tighten the lock ring.

Using a Tire (Alternative Method):

  • Less ideal due to higher air volume—it takes longer to respond and dial in pressure.

🛡️ Preventative Care Tips

  • Dirt and moisture are the #1 cause of bleeder failure.
  • Use screens on wheel receivers to block dirt.
  • Always plug wheels when washing the car.
  • Drain your air compressor nightly or install a water separator.
  • Use nitrogen to eliminate moisture-related issues.

🧪 Diagnosing Common Issues

🧱 Bleeder Doesn’t Bleed Off Quickly?

  • Likely a clogged muffler.
    • Remove the center inlet with a 7/64" Allen wrench.
    • Take out the muffler.
    • Reinstall the inlet and test again.
    • If the bleeder vibrates afterward, the muffler was clogged.

💨 Bleeder Won’t Hold Air?

  • Likely a dirty or damaged diaphragm.
  • Disassemble and inspect for dirt in the center impression.
  • If clean, re-coat with graphite and reassemble.

🔧 Full Cleaning Procedure

  1. Remove the adjusting cap and spring.
  2. Remove the nylon hose by pressing the orange donut and pulling the hose out.
  3. Detach the hose and spring from the assembly.
  4. Holding the bleeder upright, remove the back piece (diaphragm will likely come with it).
  5. Remove and separate:
    • Diaphragm
    • Fiber washer
    • Poppit
  6. Clean the diaphragm using soap and water or 409 (NOT brake cleaner).
  7. Wipe graphite off the washer and poppit.
  8. Clean the back piece and O-ring with 409.
  9. Clean the screen inside the center inlet using compressed air.
  10. Blow out the muffler from the outside-in to remove graphite buildup.

🧴 Recoating the Diaphragm with Graphite

  • Use extra fine graphite 
  • Place some graphite into a small container.
  • Drop the dry diaphragms inside and shake for 10 seconds.
  • Remove and lay them on a paper towel with the impression circle facing up.
  • Massage the diaphragm with your finger until it looks shiny.
  • Blow off any excess graphite—leftover graphite can clog the muffler over time.

🔚 Final Thoughts

Consistent bleeder performance depends on clean parts, proper setup, and preventative maintenance. Taking the time to follow these steps ensures your bleeder system maintains tire pressure accurately—and keeps you fast and consistent on the track.

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