RTV vs Gasket: What Actually Seals (and What Comes Back)

You sealed it clean, torqued it to spec, and it still came back three weeks later with a drip running down the front of the block. Nine times out of ten it isn't the gasket's fault. It's the sealer — how much you used, whether the surface was actually clean, and whether the part slid on straight.

Know Which Job You're On

A gasket and RTV are not interchangeable. A pre-formed gasket (paper, composite, MLS) needs a dry or lightly tacked surface. RTV is for stamped covers, machined flanges, and joints the manufacturer sealed with FIPG from the factory — timing covers, oil pans on a lot of imports, thermostat housings.

Anaerobic sealer is a third animal. It only cures where there's no air, so it belongs on rigid machined joints with tight tolerances — bearing caps, flanges, some case halves. Wrong sealer on the wrong joint and you're doing the job twice.

Surface Prep Is Most of the Seal

Wipe the flange with brake cleaner and let it flash. If you can still see the old sealer's shadow, you're not done. Use a plastic scraper or a brass brush — never a roloc disc on aluminum unless you like gouged sealing surfaces. Run a straightedge along the flange while you're in there; a warped cover never seals no matter what you squeeze out of the tube.

How Much Is Too Much

A 2–3 mm bead is it. Any bigger and the excess pushes inward, breaks off, and ends up in the oil pickup.

Run the bead in a continuous loop and take it around the inside of every bolt hole — not the outside. No gaps, no double passes, no finger-smearing it flat. If the spec calls for thread sealant on bolts that pass through into oil or coolant, use it there. That's a different product than the flange sealer, and it matters.

Don't Drag It Into Place

Set the cover straight down. If you slide it, you wipe the bead off one edge and never know it. Snug it in a spiral pattern from the center out, then torque in sequence in two passes. On timing covers with an oil pump behind them, the cover has to land with the pump drive and seal aligned — forcing it on is how you roll a seal lip or crack a cover.

Give the sealer its full cure time before you add oil. Ten minutes of patience beats a comeback every time.

What We Use

Timing covers are the joint that punishes sloppy technique the most — the cover has to drop on straight so the front crank seal and oil pump drive line up. We built the UR/AR/TR/GR Engine Timing Cover & Oil Pump Installation Tool for exactly that: it holds alignment so the cover seats without dragging the sealer or rolling the seal. PA12-CF carbon fiber nylon, made in the USA by a working technician.