Painting an oil pan’s interior

Question:

I’m rebuilding a 1967 Sunbeam Alpine engine, and need advice on painting the oil pan. The baffles in the pan were cracked, and the interior of the pan was slightly rusty due to a head gasket leak. I’ve reinforced and welded up the baffles and removed all the rust, but now I’m wondering what kind of paint to use on the interior of the pan. It seemed to have a very thin coat of flat black from the factory. I need a paint that will protect the steel and not flake off when subjected to hot oil and vibration. The baffles might interfere with powder coating, but paint could easily be sloshed around the pan and poured out. Any suggestions?

Answer:

I have never painted the interior of an oil pan. In theory, at least, the fact that it’s almost constantly coated with oil will prevent it from getting rusty on the inside.

If the engine sits for a very long time without being run or otherwise having the oil circulated, the inside of the pan could rust. Also, as you’ve experienced, if water ends up in the oil pan, that can lead to rust.

The potential downside of painting the inside of the oil pan is that the paint could come loose and cause trouble. I would feel a little more confident painting the inside of a brand-new oil pan.

After more than 40 years of immersion in oil, it might be difficult to entirely cleanse the oil out of the pan’s metal. For that you should consider soaking it for a while in a strong solvent such as carburetor cleaner or paint thinner.

As far as the paint goes, anything that will adhere tenaciously and stand up to the oil and its heat should work.

A catalyzed urethane such as Imron will stick and stand up to the heat. You should also consider using a paint called Glyptal. Beginning in 1925, Glyptal was the liquid research division of General Electric and in 1985 it was spun off as an independent company. For decades, engine builders have used Glyptal paint for the inside of engines to prevent corrosion, hold down bits of sand and casting debris, and help the flow of oil by smoothing out rough cast surfaces.

The easiest source for Glyptal paint is The Eastwood Company (eastwood.com). You also can buy it from places that sell the parts and supplies needed to build and rebuild electric motors and other electrical parts as they’re commonly used in that industry.