Filing the surface smooth helps seal an EGR valve when imperfections are seen on the mounting surface.

• A. False
• B. Only works on steel surfaces
• C. Worsens seal
• D. True

Answer: (D)

A smooth, flat mounting surface is essential for a good seal because the gasket relies on even contact to compress properly. Imperfections such as burrs, nicks, or pitting create high spots or gaps that prevent the gasket from seating evenly, which can allow exhaust leaks. Lightly filing or smoothing these irregularities removes the obstacles to uniform gasket compression, so when you torques the bolts to spec, the seal can form correctly under the heat and pressure of operation. After smoothing, clean the surface thoroughly and recheck for flatness; if deep gouges or corrosion remain, consider replacing the mounting surface rather than continuing to remove material. In short, smoothing the surface helps the EGR valve seal reliably.