So I finally got to look at my new rotor housing that came last week, there's a pin sized hole in it opposite the spark plugs.

Anyone ever had this happen before??

Mildly annoyed...to say the least

 

Did you check it against your old housing?

That’s the oil injection hole I think.

 

I don't have my engine disassembled yet. I see the oil injection hole, I should have been more specific, I apologize.

It's on the mating surface where the rotor would meet the iron. One looks like it had threads replied into it, the other one, while not a hole like I thought at first, is different from the surface in color.

I know mazda didn't do this on purpose obviously and if there's an issue it will get fixed. Can someone take a look and tell me if this housing looks good for being brand new ?

Threaded hole on the right near the edge of the mating surface.

Speck right below the coolant passage

 

If we are on the same page, the 1st hole you're concerned about is the hole for the pin that keeps the exhaust sleeves in place. Should be one directly opposite it on the other side as well.

The 2nd, smaller one looks like a manufacturing defect from an air pocket or similar. I would check to see if this is directly over top of the coolant seals, by comparing with a spare iron. If not, it shouldn't bother anything. If it is, it's small enough that I'd probably just try to fill it with high temp JB Weld and sand it smooth rather than deal with an exchange.

 

IMO, that housing is imperfect and should have been rejected during QC inspection. If I'm paying top dollar for a genuine Mazda part, than I'm expecting to receive a top quality Mazda part without any imperfections even if minor.

 

The pin you are seeing is the roll pin that holds the exhaust sleeve in place. The other imperfection is a common casting flaw. Many new rotor housings have them. Mazda typically fills the voids with a JB weld type material. It should not affect anything but if you are concerned clean the area, do a skim coat of industrial jb weld and shave flush with a razor blade.

 

I appreciate you guys chiming in. I appreciate everyone's clarification, actually. Thank you to everyone who replied.

That second one actually isn't a hole at all when I started examining it more closely, it looks like its already been filled in just like you mentioned.

Edit: anyone know why the rotor housing feels like it has some weird..'finish' or coating on it? It feels like its across the entire surface area.

Also, Funny you guys replied, I'm considering purchasing one of your alternators. If the S4 is limited by space, I think I will retrofit one of your upgraded S5 alternators.

 

>>> Edit: anyone know why the rotor housing feels like it has some weird..'finish' or coating on it?

Automotive parts are often coated with Cosmoline which is a rust preventive coating that will protect the part for very long storage duration.

 

Mazda coats the chrome wear surface of the rotor housing with Teflon which smears into the microporous chrome plating on initial start and the re-emerges when it gets hot and melts out. Its like assembly lube for rotary.

I think they switched to graphite for the FD rotor housings?

 

Mazda coats the engine parts with an oily spray to prevent corrosion during shipping/storage. It is removed by our cleaning process prior to assembly. New housings have a dull finish on the inside. The chrome-like appearance on used housings comes from the apex seals polishing up the surface.