Bacoeng vacuum chamber leaking and wont hold vacuum during degassing

Diagnosis

A failure to hold a vacuum in a Bacoeng Vacuum Chamber Kit is almost always caused by a breach in the airtight seal between the acrylic dome and the aluminum base, or a failure in the vacuum pump's internal valve system. Because these kits use a thick rubber O-ring seated in a machined groove, any microscopic debris—such as a single hair, a grain of cured resin, or a piece of dust—creates a "leak path" that allows atmospheric air to rush back into the chamber. You can confirm the leak location using the "Soap Test." While the pump is running and the chamber is under vacuum, apply a small amount of soapy water or a specialized leak detector spray around the rim where the dome meets the base and around the vacuum hose connection point. If you see bubbles forming or hear a distinct whistling sound, you have identified the specific point of ingress. If the gauge drops slowly even after the pump is turned off and the valve is closed, the leak is likely in the hose fittings or the pump's check valve.

How to Fix It

To resolve a leak in the Bacoeng kit, you must ensure a perfect mechanical seal and verify the integrity of the vacuum line. Follow these steps precisely:

1. Clean the Sealing Surfaces: Remove the acrylic dome from the aluminum base. Use a lint-free microfiber cloth and 91% isopropyl alcohol to wipe the machined groove in the aluminum base and the bottom rim of the acrylic dome. Ensure no residue from previous degassing sessions remains.
2. Inspect and Lubricate the O-Ring: Remove the rubber O-ring from its groove. Inspect it for nicks, cracks, or flattening. Apply a very thin, transparent layer of high-vacuum silicone grease (such as Dow Corning High Vacuum Grease) to the O-ring. Do not over-apply; a thin film is necessary to fill microscopic imperfections in the metal and rubber.
3. Reseat the Dome: Place the O-ring back into the groove, ensuring it is not twisted. Carefully lower the acrylic dome straight down onto the base. Apply firm, even pressure across the entire top surface of the dome to ensure it is seated flush against the aluminum.
4. Tighten Hose Connections: Check the connection between the vacuum hose and the chamber's intake port. If the kit uses a barb fitting, ensure the hose is pushed all the way on. If it feels loose, use a stainless steel worm-gear hose clamp and tighten it until the hose is snug but not deformed.
5. Test the Valve: Turn on the pump and evacuate the chamber. Close the manual shut-off valve completely. Watch the gauge for 60 seconds. If the needle remains stationary, the seal is successful.

If That Didn't Work

• Replace the Vacuum Hose: Cheap PVC tubing provided in some kits can develop "micro-pores" or pinhole leaks over time, especially if exposed to chemicals. Replace the current hose with a reinforced braided vacuum hose rated for at least 30 inches of Hg (mercury) to prevent the tube from collapsing under pressure.
• Check the Pump Oil Level: If the vacuum pump itself is struggling to reach the target pressure, check the oil sight glass. If the oil is cloudy or below the minimum line, the pump cannot create a sufficient seal internally. Drain the old oil and refill with ISO 100 vacuum pump oil.
• Inspect the Acrylic for Stress Cracks: Examine the acrylic dome for "crazing" (tiny internal spider-web cracks). If the dome was cleaned with harsh solvents like acetone, the acrylic may have developed structural micro-fractures that allow air to permeate through the plastic itself, though this is rare.
• Replace the Gasket: If the O-ring has permanently deformed (lost its "spring"), it will no longer exert enough outward pressure to seal. Replace the O-ring with a genuine Buna-N or Viton replacement of the exact same diameter and thickness.

Heads Up

• Avoid Acetone: Never use acetone to clean the acrylic dome; it will cause the plastic to crack and permanently destroy the vacuum seal. Stick to isopropyl alcohol or mild soap.
• Oil Maintenance: Change your vacuum pump oil after the first 5 hours of use (break-in period) and every 50 hours thereafter to maintain maximum suction power.
• Avoid Over-Tightening: If your model uses bolts to secure the dome, tighten them in a star pattern (like lug nuts on a car wheel) to ensure even pressure. Over-tightening one side can warp the seal and cause a leak on the opposite side.
• Storage Tip: When not in use, do not leave the dome tightly sealed to the base. This can cause the O-ring to flatten permanently, reducing its effectiveness for future degassing.