The inner, or, compression seal is made up of three different materials, and in olden times had a strip of steel called a seal protector along the spark plug area. I always wondered about that strip of metal, because it was on the outboard side of the seal.

 

How could it protect the seal?

 

It couldn't. It just took up volume and possibly made for more pressure along that area. Over time the pressure would migrate all around and that advantage would vanish.

 

Then Mazda quit installing the protector, and nothing bad happened. Then it was never seen again.

 

The massive pressure between the edges of the rotor housing and the iron forms the compression seal measured in tons. There is a limit to how much help you could get from any kind of flex seal or "O" ring. So if you fail part of this "O" ring you will get combustion gasses in the coolant, and if you have a system design that can get the gasses to a recovery pot or bottle where it can escape overboard, you might not blow the coolant out of the engine. At least not early in the failure.

 Many street rotaries have gone on for years using just a bit of coolant each week. Eventually the coolant is replaced with plain water and the irons begin to decompose and the engine will no longer start.  

 

The coolant enters the working chamber during cool down. When there is still pressure in the coolant. This requires that a tiny scratch has been left in place between the housing and the iron, and or, more than one loose case bolt allowing for a bit of a warp. Once you have the failed "O" ring, torque on the case bolts is of no matter. The damage has been done.

 

In the racer we just dump in a bottle of Barrs-leak. Probably not good enough in aircraft use.

 

In the racer I torque the case bolts over two days. I use antisieze on the threads and under the heads. I use silicone in the center and below the head. Even if a bolt breaks it will not loose any coolant. Use a plate held on with stationary gear bolts, so a broken bolt head cannot back out of the hole. I have had one bolt break since 1980. I torque to the lowest number in the range. This comes out to be way more torque than is specified for clean dry threads. Racing Beat says 32 pounds is max for clean dry threads for race engines. So when you see 23-25 pounds, I use 23 with antisieze..

 

You could remove the rear iron and replace just the failed seal. You should strip it down and replace all of them. 

 

One warped iron is enough to ruin the engine, so all must be checked. The rotor housings are like rubber and can be torsioned by a warped iron. They come straight again when removed from the engine (usually). 

 

This may turn out to be worth what you are paying for it.

 

Lynn E. Hanover