Toasted Oil Control Rings!!!
 

We pulled these out of my buddies SA 12a, we are in the process of rebuilding. It was smoking so bad it was not drivable. This one in the pic is the bigger one in the front side of the rear rotor. Does anyone know what could cause this?

Overheated? Check for crush on rotor housings.

??

When the oil control o-rings are obliterated like that, we usually find a failed Eccentric Shaft Thermal Bypass Valve (aka Thermal Pellet), which caused severe rotor overheating.

The quarterback....is TOAST.

Ouch! That sounds horrible. How can such a thing happen? What can we do to prevent it?

On a 12A? nothing, because they don't have one. There is a write up somewhere in the second gen section on how to bypass it for you 13B guys, I think it involves using washers stacked up as spacers.

So that applies to the SE?

HOW DO I CHECK THAT?

HOW CAN I TELL IF IT HAS FAILED?

i'd start measuring all parts for wear. the mazda factory shop manual has all the procedures and steps.

are the iron plates level or have step wear?

Only '86+ had the thermo pellet thing. The 20B and '85 and older 13Bs (and all 12As) did not. :)

There is no thermal pellet in pre 85 motors. Check the housings for warping and large amounts of wear. This includes both the housings and Irons! Looking for signs of over heating. Check the E shaft as well for the rotor oil jets. How do the bearings look? Check the lobes on the E shaft and the warpage of the shaft itself.

So we found the problem. It was the side seals. They were so stuck in the groves from the heat we practically had to tap them out with a rubber mallet, but not without breaking all three on that side. The springs are fine and I wore the groves back out with some sand paper so the seal fit in there again. So now all I have for extra side seals is FD ones. Will they fit and if so how much modification is involved? I might be able to find some extra SA ones if thats what I need to do. Let me know.

Very true. It didn't register that he had a 12A for some reason. D'oh. Anyway, it takes some serious heat to obliterate the oil control o-rings, regardless. As others have said, inspect everything.

The very first engine I ever tore down had only small pieces of oil o-ring left. The rest of the engine was very bad as well. I haven't come across any others in as bad of shape.

???

Can I use FD side seals?

No. Get some SA ones. SA ones fit '74 to '85. :D

K. Thanks Jeff.