RTV gasket makers

RTV suits flexible stamped flanges such as sumps and gearbox covers. Rigid machined flanges with very small gaps are better served by anaerobic gasket makers. Do not use RTV where the original gasket sets a spacing, as removing it changes the assembly clearance.

Acetoxy cure smells of vinegar and can corrode copper, plated steel and electronic sensors. Neutral cure is non-corrosive and safe for engines with oxygen sensors and electrical parts. Near electronics, choose neutral cure or a product marked sensor-safe.

Run a continuous 2 to 3 mm bead, circling inside the bolt holes. Assemble while wet, hand-tighten, then wait as the TDS states before final torque. Over-thick beads squeeze inside and can block oil pickup screens.

RTV cures by moisture from the outside in, at roughly 2 to 3 mm per day depending on the product. Some oil-resistant grades allow immediate filling, others need about 24 hours. Low humidity and low temperature lengthen cure.

Scrape off all old gasket with a plastic scraper or a tool that will not gouge the flange, especially on aluminium. Then degrease with a solvent that evaporates completely. Oil or old residue left on the flange causes RTV to lift and leak.

Silicone RTV typically works continuously up to around 200 to 260 degrees C depending on grade, and there are grades formulated for engine and gearbox oil. Ordinary RTV is not suited to long-term contact with petrol. Choose by the actual fluid listed on the technical data sheet.

Acetoxy RTV releases acetic acid, which can damage oxygen sensors and corrode electrical contacts. Use a neutral cure RTV labelled sensor safe. Acetoxy RTV is recognisable by its vinegar smell while curing.

RTV cures with moisture, so after opening the material at the nozzle gradually skins over. Cap it tightly, and the cured plug at the nozzle can be removed to reach usable material inside. If the contents are lumpy or will not extrude evenly, discard it since cure quality is no longer assured.