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Lots of oil/pressure in breather hose

Old 08-11-2015, 01:34 PM
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Lots of oil/pressure in breather hose

EDIT:
Faulty oil filter was the cause!

Hi!

I'm a new member, but not a total newbie. Search has been my good friend on this forum for a long time. I have had my 6-speed 6-port -04 RX-8 for a couple of years. Last winter I did my first rebuild(clutch exploded, perfect time for a rebuild). The car had about 110k then, and was only shoving first symptoms of low pressure. The cat has been gutted long before the rebuild. After rebuild I have driven about 5000km without problems. Proper break-in, commuting and few trackdays without problems.

Long story short: My engine blows a lot of oil in the intake in high rpm/high load conditions. This started suddenly and might have something to do with oil overfill, as it started about the same time that the engine was probably overfilled. Oil is now in normal level, but symptoms are the same.

Long story:
Rebuild was a straightforward job. New soft seals, new apex seals. One housing had a crack in the spark plug hole, so it got replaced. Oil rings were worn, but barely in the tolerances. Everything else was ok. New plugs, wires and coils.
Easy driving for couple of hundred kilometers, new oil and little by little some more spirited driving. Everything was ok.
I loaned the car for a friend of mine for a week. He topped the oil as I had instructed, and reported that the car behaved weirdly on the last day. He suspected that one of the coils may be bad. No CEL, no codes in memory. The car was definitely driven hard during that week(as they should be), but nothing stupid was done.

I got the car back and it was running a bit badly on idle. Throttle response was bad on low rpm's, but normal on high rpm's. The car was drivable, but started blowing a LOT of blue smoke when driven hard. I lost almost all power. Checked the oil level, and it was on the upper mark. There was oil in the MAF sensor and in the air cleaner. I cleaned everything and changed the oil. (My friend said, that overfill didn't happen. He is a mechanic, so he knows a thing or two about cars. I still wouldn't rule that completely out.)

Same thick smoke and power loss returned, when the throttle was floored for a few seconds. Once again, the MAF and air cleaner were oily. This time the oil level was normal, or maybe even a little low. I cleaned the MAF, changed the filter. I made a simple oil catch can in the breather tube, for diagnostic purposes.

This setup had even worse results. When I floored the throttle, oil started running from the breather hose. My simple catch can got some of it, but the hose connection didn't last under the pressure. This time oil didn't get in the intake, but sprayed all over the engine bay and on the fresh white plastidip on the car(nice, impossible to clean). No power loss was noticed. I would estimate, that about half a liter of oil was lost, when I accelerated first and second gear to the redline.

With the cleaned MAF and new air filter, the car runs just like it should on normal driving. Low and high rpm's are fine, until I try to get some real power out. Warm starts might be a second longer than before, but I'm not totally sure about this.

My guess is a broken side seal. Could side seals be stuck? Can anyone suggest anything less expensive?

Compression test would be informative, but I bet the local dealer doesn't have the equipment needed. Even if they did, I would never give any money to them(work-related, personal problems with management, long before I got my Mazda).
If rebuild is the only answer, this car is going to be parked for months or years, because I'm lacking the garage and the money for a new rebuild...


EDIT:
Faulty oil filter was the cause!

Last edited by uZu; 12-30-2015 at 12:24 PM.
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Old 08-12-2015, 01:09 PM
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Smarter engine guys will have to weight in, but it seems you have a lot of blow-by. That is a side seal thing. The only other source of oil would be an OMP injector with a stuck check valve. But, if you are getting oil in the catch can being fed from the oil fill, and pressure, you are likely getting blow by from a side seal and an oil seal. It could be simply just a seal that needs replaced. If you can do the work, then it might not be that expensive.

Best I got.
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Old 08-13-2015, 01:36 PM
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Thanks for your reply!

I couldn't get the idea of a stucked side seal out of my head, so I tried a little seafoaming/decarboning today. I figured it couldn't do any more harm. We don't have Seafoam in Finland, so I tried to find something similar. I found two products that might do the trick, so I used both!
First stuff in though the maintentance ports -> few hours -> second stuff in -> hour -> start. Smoked the neighborhood nicely, improved hose fittings in my catch can and took it for a test run when warm. First hard acceleration puked a little oil in the tank. Now I have driven around 10 kilometers, some of it with a very heavy right foot. No more oil in the can!

I will be doing more testing on this weekend...
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Old 08-13-2015, 08:42 PM
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Good luck.

Does you catch can feed just off the oil fill?
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Old 08-14-2015, 12:03 AM
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Yes, a hose comes from the oil fill to the can, and another hose goes from the can to the intake. It's a shame that I don't have a photo of it. Probably one of the best temporary zero budget catch cans ever. :D
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Old 08-16-2015, 02:56 AM
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The amount of oil/blow-by has reduced, but It hasn't stopped.
Maybe I should try cleaning some more?

Yes, taking the engine out and dismantling it would be the best way to go. I just don't have the garage needed to do that(and can't afford to rent one right now).

If the amount of bureaucracy and paperwork needed wasn't so huge, I would be converting this to a electric motor...
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Old 08-16-2015, 06:28 AM
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From above,

I think this only happens at the top end. When you are pulling the most power. Since you you took it easy for the first part after the rebuild, this issue could have been there all along.

If the seafoam cleaner seemed to help, good. But, there should not have been all that much for it to clean. Unless there was stuff under the seal. Did you replace the oil seals or reuse them? You mentioned they were in tolerance is why I ask.

A compression test would tell you if you lost a seal. It could be you have a compression seal that is hosed, and it is just overwhelming the oil seal with blow by.

Best I got, no coffee yet.
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Old 08-17-2015, 02:07 AM
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Edit:brain fart removed.

Side compression seals and their springs were re-used. They were measured to be fine and cleaned. Corner/side seal clearance was never measured because I thought the clearance would be ok, since they have worked for 110k without problems. The side seals are 100% surely on their original places in the rotors.
Oil control rings were also re-used, but naturally with new o-rings. They were worn almost to the limit, where Mazda recommends to renew them. Didn't see that as a catastrophic problem.

After rebuild I took it easily for about 500 kilometers(no high rpm, lots of premix). This issue could have been there then, and wouldn't have been noticed at all. The next 4500 kilometers instead would have showed the symptoms, because there was a lot of hard driving(trackdays etc.). Never during that time, was there any excess oil in the intake(opened it three times, for different reasons). That's why I'm pretty sure this started just two weeks ago.

I was expecting the cleaning to fix the issue or to do nothing at all. This partial fix was something I wasn't expecting...

Last edited by uZu; 08-17-2015 at 11:45 PM.
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Old 08-17-2015, 09:17 AM
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It really sounds like a side seal issue to me. Have you had time to get in for a compression test after your rebuild? Thats really the only way to know for sure.
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Old 08-17-2015, 05:25 PM
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Seafoam it and compression test it. No reason to tear it apart unless seafoam does nothing and compression shows something odd. (but this does sound like a side seal, sadly)
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Old 08-25-2015, 10:16 AM
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The car didn't get better...
I have parked it and will probably open up the engine when i'll buy my own house with a garage. That means months or years.
I'll try to remember to come back and post the results then.

Thanks for you all!
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Old 11-19-2015, 01:07 PM
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PR High Oil Pressure, Blow By, Oil in Air Filter/Box

My RX8 had this issue after an Oil change. I Drove it for 3 months and when I went to change the oil filter, the inside of the filter was like new. The valve never opened causing the back pressure and the spaying of oil. I changed the oil filter replaced it with a Wicks oil filter and the problem has stopped.


If you have this problem especially after an oil change, it might be a defective oil filter. Just remove the filter and if its dry or very light weight that is most likely
the issue.


Hope this helps
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Old 11-29-2015, 11:59 AM
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I took out the oil filter. It was oily, and had some oil in it. The engine had not been run in weeks. Replaced with a new one.

There is no more pressure in the breather!!

It's a shame I don't have a place to do an autopsy for the old filter, to determine the cause of death. The filter worked ok for some time, last time I changed it was about 1000km ago.

I still have some sort of a oil leak on the engine. After driving, there is some oil burning in the back of the engine. It might be dripping on the exhaust manifold. Nothing gets to the ground. It is possible, that this is old oil spill from the earlier oil disasters that originated from the breather when my catch can failed. I'll keep you posted!
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Old 12-30-2015, 12:35 PM
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I sourced the oil leak to the oil pan. I took it out, and put new sealant in. All is good now!

The bottom part of the oil pan wasn't flat anymore, it had bulged a bit. No harm there, just a bit more oil capacity now. :D

This 8 is now back as a daily driver. We also got snow in Finland just last week, so the timing is perfect. Snow and winter tires means lots of fun!
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