Rotary Teardown #1 - Vax's Engine

This weekend I finished tearing down a customer's rotary engine (13B) from an RX-7, and I figure I'll post the results here, and clarify what the pictures mean. This engine is out of a Series 4 Mazda RX-7, it is the Naturally Aspirated version of the engine, meaning it did not come with a turbo. This engine (I believe) has over 150,000 miles on it.



This is the engine with the front cover first removed. You can see the oil pump with the chain around it, and the CAS (Crank Angle Sensor) worm gear on the nose of the eccentric shaft. Everything here looks normal for an engine with high miles except for that counterweight . . . .



The front counterweight is usually coated in oil. This coating drips off if the car sits for a long time. With the protective coating of oil gone, combined with moisture from some short distance driving (where the engine did not have time to warm up and steam off the water) probably caused this rust. The oil pump also had some small scratches on the aluminum internal arm, indicating that old or crappy oil had been used, as even high mileage 13B engines tend to have very little wear on the oil pump.




With the rear iron removed, you can see the rear rotor. I could immediately tell that it was blown because two of the apex seals were retracted into the rotor. Normally they are pressed firmly against the housing, it's not easy to tell in this small version of the picture, check out the larger version here and look at the topmost seal. Note the distance between the seal and the housing.



Here, we can see that when the apex seal blew, it took a chunk of the rotor with it. Those parts flying around in the combustion chamber took out the housing. All would have to be replaced if the customer desired to have this engine rebuilt.


This is one of the many scratches on the rotor face left by the apex seal.

Here, I'm cleaning out the coolant passage of the front rotor housing. This is the better of the two, in that it's not completely blown by having a metal seal smashed into it repeatedly.



My guess is that this is the result of mixing Dexcool with the regular green coolant. Some people think that it's the result of too much tap water and stop leak. Personally I've seen the results of using "Bar's leak," and it's not this bad.



Again, the better of the two rotor housings. You can see the gouge left by the corner seal in the surface of the housing. Also you should note that the housing is shiny, it's not supposed to be, it should have a whitish matte finish over the metal, it's a special oil retaining coating to prevent stuff like this from happening. High miles and crap oil is my guess for what happened here.


The one perfectly decent internal part recovered (not counting the obvious stuff like the eccentric shaft). The front rotor. It is a "C" weighted rotor, so it will need a similarly weighted rotor to replace it's brother that was lost in the line of duty. This rotor can be cleaned up and returned to service.

For larger versions of all these pictures, check out my photobucket album. Feel free to ask any questions in the comments section.