Classic Motorcycle Build

Anaerobic Gasket Sealer Review

(Article by Mark Trotta)

Some may think anaerobic sealant is too expensive and dismiss it for that reason. But when you consider it's advantages; ease of use, easy clean-up, no harm to oil circuits, and indefinite shelf-life - all of these justify the extra cost to me.

best sealant for engine cases

Silicone Sealant Concerns

Starting in the seventies, silicone sealants began replacing gaskets in many automotive applications. Today, silicone-based sealants are the most popular with professionals and DIYers. But on a motorcycle engine, no matter how careful you apply them, there is always a risk of unwanted globs ending up in the oil circuit.

There is also another concern for motorcycle engines. Any fuel dilution in the oil will eat away at silicone engine sealant. This is problematic for older, carbureted engines.

anaerobic sealant for engine cases

If gas leaks through the carb while your bike is on it's side-stand, the unburned gas gets into the oil, and dissolves silicone sealant. Why take the risk when you don't have to? You have other choices.

What Is Anaerobic Gasket Sealer?

Anaerobic literally means "lives without air". So, anaerobic sealer only cures when you take the air away from it (like when it's between engine cases). If you apply a little extra, it doesn't harden and clog oil passages in the engine.

Permatex Anaerobic Gasket Maker

Since it only hardens in the absence of oxygen, you have more time assembling and tightening down the case bolts. This is a welcome relief for me, because I like to work slowly and methodically. There is no pressure to get parts bolted up quickly.

Permatex Anaerobic Gasket Maker

Permatex #51813 is an OEM specified liquid gasket that cures in an airless environment. It is advertised as a non-corrosive gasket material, designed primarily for use on aluminum, iron, and steel flanged mating surfaces. When a conventional gasket is unavailable, it will fill small imperfections in mating surfaces up to .015".

Surface Prep

Before any sealant is applied, engine cases need to be clean, flat, and dry. To be fair, some builders don't take surface prep seriously enough, and then blame the sealant for not doing it's job.

anaerobic gasket sealer review

Take the time to get the mating surfaces completely clean and oil free. The engine cases also need to be flat. This is of particular importance when an aluminum case was repaired by welding, which often distorts and warps the metal.

After surface prep, wipe on the sealant with a gloved finger. After the engine cases are joined and tightened, there will be a small but even amount of "extra" sealant that squeezes out of the surface faces.

best sealant for engine cases

Excess sealant can be wiped off with shop towels.

best sealant for engine cases

Anaerobic gasket maker cures to a solvent-resistant seal and does not tear or decay during service.

anaerobic gasket maker for engine cases

Shop: Anaerobic Gasket Sealant

It's also available in a caulking gun size, which dispenses easily.

anaerobic flange sealant for engine cases

Shop: Anaerobic Sealant, 300 ml Cartridge

If you think it's a little pricey, consider this: the glob in the picture below was all I needed to seal my Sportster engine halves.

best sealant for engine cases

Because it doesn't harden until oxygen is removed, any unused portion will last a long time. It doesn't harden in the tube, so it stays usable for a long time.

Another advantage of anaerobic gasket sealer is that parts disassembly is easy. Even after extended service, old gasket material is removed easily with a razor blade or gasket scraper.

remove gasket sealer from engine cases

Is An Activator Needed For Anaerobic Sealer?

The package instructions mention using an activator spray, or surface prep spray, which confuses some people. Permatex states that the activator spray is only needed when you are sealing porous surfaces.

Permatex Anaerobic Gasket Maker

Anaerobic sealant works very well with aluminum engine and transmission cases. It also works well on outboard motor crankcase halves.

I still use silicone gasket maker on automotive uses such as water pumps and such, but nowhere oil related. No matter how careful you apply it, there is always a risk of unwanted globs ending up in the oil circuit.

Why take the risk when you don't have to?

anaerobic gasket sealant for engine cases

Shop: Permatex Anaerobic Gasket Maker