Rick's Free Auto Repair Advice

RTV gasket sealer mistakes

Avoid these RTV gasket sealer mistakes

RTV gasket sealer mistake #1 — improper surface preparation

Failing to clean off the old gasket material is the #1 cause of future leaks, especially when using RTV as a form-in-place gasket. Why? Because silicone gasket material doesn’t stick to itself. If you leave any old gasket material, the new RTV won’t stick there and will leak.

If you need to scrape the surface, use a plastic scraper or stiff nylon brush; never a razor blade.

RTV gasket sealer mistake #2 — using a gasket sealer on paper or cut gaskets

Using RTV on paper or cut gaskets. Unless otherwise noted in the shop manual or instructions packaged with the parts, these gaskets are usually designed to be installed DRY. In those cases where the instructions recommend a sealer, use the recommended gasket treatment.

If the gasket contains a rubber bead, NEVER add any type of gasket sealer. Those products will prevent a complete seal, resulting in leaks.

water pump gasket sealer

In cases where you need a gasket to stay in place while installing the part, use a high-tack, non-hardening product like  Permatex® High Tack™ Spray-A-Gasket™ Sealant or  Permatex® High Tack™ Gasket Sealant

RTV gasket sealer mistake #3 — using a gasket sealer on rubber or silicone gaskets

These gaskets are designed to be installed dry. Applying RTV can cause actually lubricate the gasket and cause it to “squirm” during the application, preventing proper alignment. This is a case where applying RTV can actually cause a leak, rather than prevent it.

RTV gasket sealer mistake #4 — Using too much RTV

Excessive RTV application will simply cause the RTV to ooze outside the flange area. Later, as oil contacts the surfaces, that excess RTV will dislodge and cause oil gallery obstructions or clog filters or screens.

RTV gasket sealer mistake #5 — Not allowing proper cure time

Anaerobic RTV sealers are designed to be applied and set in place and then set up in place for about 1-hour before you torque to spec. Refer to the product’s instructions for recommended set-up times. In addition to set up time, many RTV materials must cure for 24-hours before being exposed to fluids.

If you need to return the vehicle to service without waiting, use an RTV material that’s specifically designed for that immediate use.

On the flip side, never allow a solvent-based gasket sealer to dry completely before installing the component and torquing to spec. Some solvent-based gasket sealers will begin to “skin over” if left to dry and the skin won’t seal properly.

RTV Gasket sealer mistake #6 — Using an RTV sealer on an application that’s exposed to gasoline

RTV gasket materials aren’t appropriate for applications in contact with gas. Use a solvent-based product in those applications.

©, 2020 Rick Muscoplat



Posted on by Rick Muscoplat

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