Loctite SI 5900 Flange Sealant

The Loctite SI 5900 Flange Sealant (formerly Loctite 5900) is a black, heavy-bodied oxime silicone that forms gaskets in place on stamped sheet-metal covers such as timing covers and oil sumps. It resists engine oil well and cures into flexible rubber with 400% or more elongation, so the seal copes with plenty of flange movement. It fills gaps up to 6.35 mm and works from -55°C to +200°C. This is the 300 ml cartridge.

Run a bead onto clean, grease-free flanges and bring the parts together within a few minutes, as moisture in the air starts the cure straight away. The heavy body lets assemblies pass low-pressure line tests before cure, but give it around seven days before heavy service loads, and keep it away from pure oxygen, chlorine and strong oxidisers. Consult the Safety Data Sheet before use.

At a glance

• Timing covers and oil sumps — stamped sheet-metal cover gaskets
• Engine and gearbox housings — oil-resistant formed-in-place gaskets
• Pump and compressor covers — flanges with high joint movement
• Uneven or damaged flanges — replacing cut gaskets in the workshop

Full specifications, applications, features and important limits are in the tabs below.