Strange ?corrosion? on rotor
 

Finished cleaning up this rotor and found this damaged area. It looks like pitting that spread into the apex seal groove. None of the seals on this rotor were damaged, this was just happily hanging out underneath.

I have two questions and please don't slay me on this one: Would this be usable? The rotor is perfect everywhere else and the corrosion is not visible in any form. I understand this would weaken the rotor at a critical location, but the motor is not going to be built for high boost.

Lastly, has anyone seen this before? Is this a common occurrence? It seems to me that this would be a very difficult place for any corrosion to take hold.

Looks like water/antifreeze corrosion. If its only that one corner seal and your running stock, i think it would hold up

did you buy this rotor from someone or was it from your motor?

if you bought it id try and get some cash back if you paid "going-rate" for good rotors

if that doesn't go through to oil, and the grooves are in spec, it should be ok. that area sees oil on one side and gas/oil/carbon on the other, so it doesn't usually rust...

This was pulled from my motor with 110k on it. It would be hard to believe it was caused by coolant as the coolant seals were still intact on this motor.

I'm betting it's void in the material from the casting process. As said before, it's ok if it doesn't go through to oil. The one lower right (first pic) looks like a wear spot from the wire type corner seal spring.

thats not a porosity void from casting. if it were it would never have made it past initial qual in the factory. either manufacturing or receiving factory.


do you have a build thread? id be interested to see what a turbo motor with 110 on it looks like

If it was a monday or friday it probably did lol

I'm working on it now but I don't currently have a thread. I will get one up soon though.

I'm now positive this is what happened! :lol:

would be interesting to see how dirty everything is and what the various seals look like with 110k AND a turbo on them.

It was very dirty on the outside. This is my first rotary rebuild, so I don't have a trained eye for what is usable and what isn't, but it doesn't seem too terrible.
Coolant seals were intact, the rotors had a lot of carbon on them but none of the seals seemed to be stuck or anything. It was leaking a lot of oil from the front cover/oil pan/omp. The housings are my main concern, as they are showing a bit of chrome wear on the edges.

were there any signs of a previous rebuild?

No it does not appear to have been rebuilt whatsoever. Still has the 3 piece apex seals

that one looks pretty nice, the water jackets on yours are really clean, usually they are all pitted and rusty.

the wear on the rotor housing is by design, they made the triangle of the apex seal smaller so it seals better, but then it also wears the housing right there

Yeah the corrosion is very minimal. I have media blasted the housings. I'll get some better photos up.

Here are photos of the internals with minimal cleaning done so that I can check the dimensions. Just wanted to give everyone a look at a turbo motor with 110k on it as well as get a second opinion on some of the wear.

Starting with the rear iron, there is minimal step wear and warpage within limits. I feel that it is usable.

Rear rotor housing: This one was giving me 82psi and I think it was either the apex seals or the groove cut into this housing. It is only a couple of thousandths (in) deep and it is showing some chrome flaking near the exhaust side. I don't know if I should chance using it or not.

Center iron has not been measured at this time but looks good.

Front housing: This one has chrome wearing in multiple places but primarily near exhaust side there are a couple smaller areas around the housing that I am concerned about, maybe someone with some experience can chime in.

Front iron has not yet been measured but looks fine.

What would you use/replace? I know it is difficult to tell in the photos but I did the best I could with this camera. I also understand that new parts are always going to be better, I just fear that I may let a very minor issue prompt replacement of something that may not need it. This is my first rotary build so any input would be greatly appreciated!

Photos cont..

did you run premix?

I bought the car when it had 108k on it so I really don't know if the PO ran premix. The short time I ran it, I premixed a small amount with the OMP running, but that was only 2k miles.

That corner seal wear looks kind of deep for 110k miles. I tore my engine apart at 162k (original engine that came with car) and it didn't look that bad. PO did not premix.

Maybe it's just the pics though.

well if you bought it with the OMP in tact and hooked up thats probably a good indication that the PO used it at the very least. i guess that means it was either premix + OMP or just OMP. but not premix only. if that logic is sound

so i thought something looked funny...the motor when its on the stand is inverted from what i would have expected. granted you are doing a teardown so it doesnt really matter.

when doing a rebuild theres a torrington bearing that needs to stay put and can slip if the motor is rotated over before its all final torqued. theres some good videos online of 13b rebuilds. one in particular is 2 parts and about an hour long total. it goes over filing the side seals, how NOT to install a corner seal when test fitting etc. its really good. you should grab a beer and watch it.

also look at mazdatrix website about that torrington bearing. they have some good info of what happens when things go wrong and how to prevent it during a build. Aaron cake also has some info on it (i think).

Was that reply to me or the OP?

My car when i first bought it, The OMP worked for about 100 miles before it took a dump. It didnt take out the ECU so for that reason I know it went into 50% duty cycle failure mode. I replaced it very quickly and the engine ran normal, but it was drastically worn out. Right before I replaced the engine it was 85-80-80 on the rear and 65-60-60 on the front. On the front iron I had not one coolant seal crack but THREE, all mostly on bottom exhaust side. 3 cracks there is very rare.

New engine tested at 120 on all faces of both rotors. :nod:

Even after 162k on the original factory motor, and even with its low compression, The rotor housings where just barely out of spec when it comes to side seal wear. When I say barely I mean BARELY, but I went ahead and chose to get brand new housings and not risk it. By the way, brand new housings are god awful expensive.:eek:

mine was to the OP.

i think his car is an s4 motor/junk so it would be a mechanical OMP not computer driven