The test valve, code 135801, is a specialized component used in the MAN L21/31 engine to enable controlled access for pressure testing, system diagnostics, and maintenance procedures. Installed at designated points within fluid or air systems, it allows technicians to safely measure pressure, release trapped media, or verify system integrity without disrupting normal engine operation. Engineered for precise sealing and ease of operation, the valve ensures leak-tight performance under varying pressures and temperatures. Manufactured from robust, corrosion-resistant materials, it offers long service life even in demanding marine and industrial environments. By facilitating accurate diagnostics and preventive maintenance, the test valve plays a key role in ensuring operational safety, system reliability, and efficient engine performance.