Anaerobic Gasket Sealer Review
(Article and Pictures by Mark Trotta)
Some may think anaerobic sealant is too expensive, or it's too high-tech for an old motorcycle. But even us graybeards have to consider it's advantages; ease of use, easy clean-up, and no harm to oil circuits. It also has an indefinite shelf-life.
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.
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.
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.
Does Anaerobic Gasket Sealer Have An Odor?
There is a very light smell, but nothing nasty.
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".
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.
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.
Excess sealant can be wiped off with shop towels.
Anaerobic gasket maker cures to a solvent-resistant seal and does not tear or decay during service.
Shop: Anaerobic Gasket Sealant
It's also available in a caulking gun size, which dispenses easily.
Shop: Anaerobic Sealant, 300 ml Cartridge
Because it doesn't harden until oxygen is removed, any unused portion will last an indefinite amount of 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.
If you think it's a little pricey, consider this: the glob in the picture below was all I needed to seal a pair of Sportster 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.
Anaerobic sealant works very well with aluminum engine and transmission cases. It also works well on outboard motor crankcase halves.
I haven't given up on silicone gasket sealants. I still use them on automotive valve covers and water pumps and some other things, but nowhere oil related. No matter how carefully you apply it, there is always a risk of unwanted globs getting into the oil circuit.
And why take that risk if you don't have to?