Confused after engine tear down.
 

My engine was rebuilt about 8 years ago, but sat until last summer when I finally got around to installing it. Unfortunately, it had a tremendous smoking problem, which I thought I had diagnosed to bad oil seals. I decided to remove the engine and rebuild it myself.

Upon removing the exhaust manifold, my diagnosis seemed to be confirmed, as I was able to peer into the exhaust ports and see pools of oil sitting in the bottoms of the housings. I thought to myself "aha, yes it's bad oil seals." Now, I'd assumed that what had happened is that the engine sat so long before being installed that the oil seals dried out, shrank, or otherwise lost their sealing ability. I've read on the forum that this is something that can happen on occasion. However, I am confused now, because today I removed the oil seals from the rotors, and they look perfectly fine. They are not dried out. They don't seem to have shrank. They are totally pliable and look like they just came out of the package...

So what's the deal? Could they be bad somehow and still look and feel fine? Is there another mechanism by which oil could be entering the combustion space (yes I eliminated the PCV valve as a possible culprit, removing the oil filler cap didn't change a thing)?

The only peculiar thing I noticed is that the inner seals were green, as I believe the stock Mazda ones should be. But the outers were black (perhaps viton?), had a smaller sectional diameter, and did not "fill the groove" of the ring; there was a lot of wiggle room. So maybe they were the wrong item?

Any thoughts are greatly appreciated. I'd love to get this thing back together before the summer.

-James

Did you have it ported by chance?

The oil control rings as you describe them (green/black) are the correct OEM parts.

it's possible that the metal oil control rings and/or springs were installed improperly.

Also interested in knowing about portwork :)

leaky compressor on the turbo would send oil into the engine. Did you check out the turbo and intercooler pipes/ upper intake for oil residue?

+1 checking the oil in IC/piping

how are the oil control ring springs? if they went flat/jammed they wont create a tight seal

Checking for oil in the intake piping is something I did prior to tear-down when I was trying to figure things out. Everything from the turbo exit to the throttle body is absolutely dry as a bone.

The engine is ported (this was a surprise to me, I didn't ask for it to be) with what looks to be a very mild street port. I think the ports are only extended on the top side, but I will post pictures of them when I get home from work to see what you guys think.

Another thing I found is that the rotors are, I believe, TurboII rotors. I don't think that has anything to do with the issue though.

time to look deeper...

were BOTH rotors full of oil? or just the one? if its just one, are there any nicks on the side irons? i saw one back in the day, where it would smoke for an hour or so after a start, and the guy who ported it nicked the iron with his grinder...

Here are some pictures of the porting, though I don't believe the porting extends to where it should not:

http://www.mcdonaldindustries.com/ja...1DSC03795R.jpg

http://www.mcdonaldindustries.com/ja...1DSC03796R.jpg

http://www.mcdonaldindustries.com/ja.../DSC03615R.jpg

http://www.mcdonaldindustries.com/ja.../DSC03616R.jpg

Also, could someone tell me if this is a TurboII rotor please?

http://www.mcdonaldindustries.com/ja.../DSC03619R.jpg

Thanks.

delete.

Any other ideas / comments?

Yes, both housings had oil puddles in them. There was enough oil that I could spin the motor by hand and watch the apex seals scoop dollops of oil up and burp it out into into the exhaust manifold.

When the car ran it made a very large smokescreen, even at idle.

How long did you run it for to give it a chance to clean itself up? My first rebuild smoked for quite a while.. Basically all the rebuild oil got thrown into the exhaust system. Not to mention all the extra oil already in there because I had tried to bring the compression up using oil.

I would say any oil after the initial hour of running is a problem. I set the idle to 1500RPM and pointed the exhaust pipe away from the house and into a block of plants in my back yard.

how long did you let the engine run for and sit between startups?

i ask because they did go a bit overboard with the 3M roloc discs cleaning the iron faces, the small swirl marks will allow oil to seep by when the engine isn't running. they will disappear over time but not nearly as quickly as it would had they lapped the surfaces or not gone so crazy with the sanding disc.

only other idea i have is that the oil control seal springs are in the rotors in reverse order.

you can always try thicker oil and let the engine run for a bit to get rid of the grinding marks or have the irons sent out to be lapped to get rid of the swirl markings so they can break in properly.

first startup expect the engine to smoke for a good 30 minutes or so depending on what they used for assembly lube. that is a minimum amount of time for parts to start seating in for the first startup, idling at about 1500 or so RPMs.

also make sure there are no pits in the oil seal tract, the first picture is a little difficult to tell whether that is a damaged face or dirt stuck to some oil.

I may be seeing things, but did that porting make a hole in upper right of the port on the rear iron?

It also looks like there is substantial pitting where the oil control ring would run in this picture

http://www.mcdonaldindustries.com/ja...1DSC03795R.jpg

Ports look to be within the safe bounds. I remember a really long time ago, a customer had a engine that was smoking, and he had the engine rebuilt 3 times from a very experienced rotary shop. Still smoked. So I did a process of elimination when we tore it down. Made a fixture to pressurize the rotors with oil in them. Sure enough one rotor had a crack inside the side seal groove. Nobody would ever see it. But it smoked like crazy. Might want to look into that. I can explain how to make a pressure tester if you need it.

I have seen a motor that has been milled for 3mm apex seals where the apex seal groove broke into the oil passages in the rotor.

Dale

Seen the same thing myself. Was damn near impossible to diagnose as you couldnt see it until the rotor was heated up. Car would shoot the oil dipstick about 10 feet in the air if you held it in for about 5 seconds. Car smoked pretty excessively and would blow the seal on the oil pan.

This motor is using RA seals.

I will probably not be able to look into things any further until I get all my parts cleaned up. Have to put together my parts washer.

The rotor pressure tester sounds like something I might need to know more about.

This is all very frustrating. I've owned the car for 8 years and have never gotten to drive it.

I think that is dirt that you are seeing in this picture but I have to check to make sure (I'm at work right now). As to your first question, I saw that in the picture also and did a double-take but it's really just a very weird shadow. There is a very shallow divot in the port but for some reason the light makes it look like a giant hole in that picture.

Hey guys, I appreciate everyone's input. I think I've got it figured out. My oil seal springs were mixed around opposite from where they should have been (guy had the gear side on the open side and vice-versa). I'm glad I put everything into organized zip lock bags when I took it apart otherwise I would not have been able to figure this out!

Do you guys think that reversing the oil seal springs could cause a really huge amount of smoking like I was experiencing? (I hope you say yes :) )

Thanks,
James

We have torn down at least 3 engines that had the oil control springs in backwards, and not in the lock tabs. None of them had oil smoke issues :/

OK guys, what do you think about this...

Strange erosion/crack in outer oil seal groove. It looks like something sat in the groove and ate away at it, or it is a casting issue:

http://www.mcdonaldindustries.com/ja.../DSC03812R.jpg

You can see here how the floor of the groove has a rough, undulating surface, like something was eating away at it, and whatever caused it also made the wall of the oil seal groove have an undercut. This goes about 1/4 of the way around the circumference.

http://www.mcdonaldindustries.com/ja.../DSC03814R.jpg

On the opposite side of the same groove, there is this. Again, looks like something sat on the metal and ate away at it, or it's a casting error:

http://www.mcdonaldindustries.com/ja.../DSC03817R.jpg

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So my current theory is that the crack/erosion area in the first picture goes all the way through the rotor wall at some point, and this is allowing oil to pass through from the hollow rotor interior, and that is the cause of my smoking.

There was a much larger oil puddle in this rotor's housing than the other. And I'm thinking oil got sucked into the other one on overlap.

What say you, rotorites?

I say you save your self a huge headache and send it to a rotary specialist shop to get rebuilt

Gee thanks.

I can assemble the engine properly. I'm just trying to make sure there is no hidden issue that will cause the engine to continue to smoke, even if I "do everything right". I thought someone might have seen similar issues before. Am I not allowed to ask the forum for opinions/help?

How does one become an expert if he is always told to send his problems to the experts?

Sure but I was just putting in my 2 cents on possibly saving you a huge headache in the future if things don't go as planned that's all.

Definitely looks like that would be the problem, in the first pic it looks like the inner oil control groove has a hole blown right through it.

Easiest way to test would be to make something to pressure test the rotor, if you cant tell by looking at it.