This model comes with an adapter, 12.5 mm female (internal thread) × 1/4″ male (external thread), which lets the breather be fitted to necks sized for a 12.5 mm mounting diameter while still connecting via the standard 1/4″ thread — common on the crankcases of piston compressors with a displacement of roughly 1 m³/min and a working pressure of up to 12.5 atm (the 4V-1.05/12.5 class and its equivalents).
Technical Specifications
| Parameter | Value |
|---|---|
| Purpose | Breather valve (crankcase vent) for a piston compressor |
| Kit contents | Plastic breather body + adapter, 12.5 mm (female) × 1/4″ (male) |
| Adapter thread, internal | 12.5 mm |
| Adapter thread, external | 1/4″ (BSP/tapered inch thread — confirm with supplier) |
| Body material | Plastic (polyamide/ABS — heat-resistant) |
| Protective cap | Ribbed, red — shields against dust and dirt |
| Compatibility | 4V-1.05/12.5 piston compressors and similar models (incl. ~7.5 kW units) |
| Operating temperature, °C | to be confirmed against the compressor’s datasheet |
| Weight, g | to be confirmed |
Design Features
The breather’s body is plastic, with a threaded fitting and a ribbed red protective cap — the ribs increase the breathing surface for airflow while shielding the internal filter element from direct exposure to dust, debris, and oil spatter. The 12.5 mm (female) × 1/4″ (male) adapter ships as a separate piece in the kit, which is convenient: it lets the same breather be used on necks with different mounting diameters without swapping the valve itself.
Installation Guidelines
- Stop the compressor and let the crankcase cool down.
- Unscrew the old breather and clean the neck’s threads of old sealant and oil residue.
- Screw the 12.5 mm (female) adapter onto the neck, then screw the breather onto the adapter’s 1/4″ thread.
- Use PTFE tape on the threaded joint for a proper seal if needed.
- Hand-tighten until snug, then give it a light additional turn with a wrench — don’t overtighten, to avoid stripping the neck’s threads.
- Start the compressor and, after 10–15 minutes of operation, check the fitting for oil leaks.
Common Installation Mistakes
- Installing a blind plug instead of a breather — pressure builds up in the crankcase and oil is pushed out through the seals.
- Mixing up the adapter thread — trying to screw the breather directly onto the neck without the adapter when diameters don’t match.
- A clogged breather filter — produces the same effect as a blind plug: pressure rises and oil is forced out.
- Overtightening during installation — risk of damaging the adapter or neck threads.
FAQ
Why is the adapter included in the kit? It reconciles the crankcase neck’s mounting diameter (12.5 mm) with the breather’s standard 1/4″ thread, allowing the part to be fitted to compressors where the factory thread differs from the breather’s own.
Can the breather be used without the adapter? Only if your compressor’s neck thread is already 1/4″ — in that case the adapter simply isn’t used.
How do I know it’s time to replace the breather? If oil is leaking from the neck, you hear a hissing/whistling sound, or the breather is visibly clogged with dirt, it’s time to replace it.
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