Lynn E. Hanover

There is no need to overheat the engine to get one of these. All you need is the luck of the draw. A core shift while pouring the iron into the mold gives you a very thin section at one of two locations. Then the seal groove is machined through this thin area and it almost cuts through the iron that is left. You can find this in engines that are running just fine, but the overheated engine is stressing both seals to stay alive and the hot side aluminum adds pressure to the iron, and "Pop" the piece comes off. Then the inner seal cannot contain the pressure and starts to leak into the water.



Rather than admit to the problem, and change the core mold, and "loose face" for some senior engineer or official, they endanger Mazda and the whole rotary engine world and keep it up for several years.



Years after they knew they had a very big problem, they let people all over the world eat these engines and build the "bad" reputation of the rotary. The people involved should not only have been fired, they should have been hacked to pieces.

But that is just my opinion, I could be wrong.



There are some fixes, if the iron is in really good shape and funds are low. I have seen one fix where you mill out a shallow area around the failure. So that the bottom of the milling gets into some area of solid iron. Then a piece of iron gets a groove milled into it to match up with the existing groove. The piece just sits in place. The inner end of the milling being bigger than the outer end, so pressure cannot move it. The stack clamping it in on assembly. In a less interesiting repair, the damage area is machined away and the resulting gap is brazed up and remachined to replicate the missing iron. My idea was to turn a large diameter cast iron shaft, maybe 3/4" or 1" with a very fine thread. Bore away the damaged area and on through the water jacket to daylight. Then thread it. Screw in the shaft. Mill it flat and reinstall the groove and braze the shaft in place. The correct fix is to drop it in the trash, or use it to practice your porting skills.



In the RX-8 the seal grooves are back in the rotor housings where they should have been all along.



The Bando P/N for a no idler water pump drive with Mazda Comp pulleys is

RPF2225. It is in the automotive catalog.



Lynn E. Hanover

toddp31

I always wondered why they moved the seals from the rotor housings to the plates and then back again.

Jeff20B

That's kinda like the beehive oil cooler on the '83-'85 12As. A mistake on Mazda's part.



Lynn, I like the 'yoohoo' belt.

rowtareh

I hope my engine won't end up looking like that. In the 2nd picture, where the indentation is, is where the coolant seal blew, right?



I am still trying to figure out these rotaries man, it is all new to me. I need to stop hanging out in General Discussion and hang in here.

Lynn E. Hanover

Well,



I think the problem is actually that the cast iron below the seal failure has broken off and let the pressure that has leaked past the inner compression seal leak into the water. From the "O" ring engineering stand point it does not matter if the "O" ring groove is in the iron or the aluminum, or half way into both, the "O" ring performance would be adequate.



However in one series of engines with the "O" ring grooves machined into the iron there were constant problems with core quality and shifting cores that too often resulted in fatally damaged engines. In the case where an engine was overheated for some other reason, this thin area could not stand up to the added pressure in the stack as the rotor housings get longer with the heat, and snap off a piece as in the picture. On engines without the problem it will not happen, so the design is not at fault, it was the execution in the production department.



Lynn E. Hanover

banzaitoyota

It boils down to ineffective quality control at the casting plant

rxrotary2_7

ive seen it a few times on high milage n/a motors in the past. i was under the impression it had a *little* to do with the factory, but also from pitting in the housings from the coolant getting so bad it just breaks....

heretic

It's so you can't mix 3mm seal rotor housings with 2mm seal side housings, and vice-versa.



I haven't been able to determine where, exectly, the 2mm seal housings are different dimension-wise from the 3mm seal housings.

White_FC

Arrrghh!

Damm this just happened to my rebuilt engine I just did.



I thought it was my fault but after reading this i'm hoping it was just a casting problem and could've happened to anyone.



So, it happened to my intermediate iron, it has been ported and has _very_ little wear on it, I'd Reaaaaly like to fix it instead of buying another one.



I know its dodgy.. So don't tell me that



The missing (yes, _missing_) bit of iron is slightly less than 2cm in length, luckily it's in a spot nearly half way up, so there is alot of casting between the inside of the water seal and where the combustion chamber is, hopefully that'll mean less pressure on the seal. Or am I just wshful thinking here?



So any ideas on what to do? Lynn E. Hanover?

I know it's a pretty big chunk to fix by the methods you describe .. I think.



I was thinking about just devcon'ing the entire area? obviously would not hold up for ever, but if it lasts a few months i'll be happy, what do you guys think?