oil blow-by

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As the title stated I have an issue with oil blow-by. Or atleast I think thats the issue. I have a 92 B6 8v, very recently torn down and honed, with fresh rings in attempt to fix the issue. I have a .5L water bottle as a catch can in-line between the pcv valve and the intake. After less than 300 miles of highway driving the bottle is overflowing oil into the intake causing the oil to burn, boging the engine down. In town, I drive 200 miles each way to work, mostly freeway, after 3 days its full. Any ideas?

[crazyrog17]

Bad baffle allowing oil into the PCV?

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I've taken it apart and sealed it with quality rtv in place of the paper gasket. Then engine has roughly 180k before the freshend up. Still ran great, but thought the fix would be rings. No change in the amount. The engine pulls A LOT harder than before the new rings.

[crazyrog17]

How silly would it be to make the catch can route oil back into the engine?

[georgeb]

You drive 200 miles each way to work? That's got to be some sort of record.

[blkfordsedan]

I have the same issue with my B3. It runs great, doesn't smoke out the exhaust, but blows a quart of oil out the breather every 100 miles. I had to disconnect it from the air intake because it would fill the VAF with oil within a day. Basically, total compression ring seal failure.

I would run a dry compression check, then squirt some oil in the cylinders and re-test. If the pressures are low and/or increase significantly when oil is added, it's a sure sign the rings are toast. If not, you know something else is going on.

When idling, you should be able to pull the oil fill cap off and have vacuum in the valve cover, not pressure (as long as the PCV valve isn't plugged). Mine has soo much pressure, if you loosen the cap and let go, it will blow the cap 6" into the air.

BTW- How many miles since the re-ring job? Did the rings ever get properly seated? How did you break it in and what oil did you use?

[blkfordsedan]

How silly would it be to make the catch can route oil back into the engine?

Usually, the oil in the catch can is pretty nasty. If it's caused by excessive blow-by, it usually has a lot of moisture and gasses in it from combustion. I wouldn't put it back in the motor unless the motor is completely worn out and I didn't care about how long it lasts.

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The 200 miles is a typo. I ment 20 each way. I have put about 2k on it since the freshen up. I messued the ring end gap before installing them onto the pistons keeping them with the measured cylinder. They were at the end of the tolerence, but still acceptable. I used coventional 5w30 for a 500 mil
e break in. After initial start up, oil pressure reached good level, I held the idle at 2500 for 2 mins to seat the rings.

[blkfordsedan]

I'd do a compression test. You may still be able to get them to seat.

[FestYboy]

did you offset the endgaps arround the piston, have you checked the PCV valve?

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When I installed the pistons in the block I followed the positioning directions from alldata directly. IIRC 1st ring 30 deg to right of wrist pin second ring 30 deg left of pin, oil rings 90 deg of pin opposite sides. I've replaced the pcv valve with 3 different brands.

[boydg1]

.... I was told by a guy who has rebuild many Festive never to re-bore, "if you do you might as well put a case of oil in the trunk". Just replace the rings, prisons, wrist pins and connecting rods even if the old ones check out ok.:cry_smile:

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[iceracerdude]

I redid my b6 and I can't imagine why the festy rebuilder would say that. It doesn't use a drop of oil, and I rev it as high as the red line and it's blown with 10 psi to boot!
The way a pcv valve works is, at idle when the vacuum is at it's highest, (there is an exception to that, but I'll address that later)the pcv valve actually closes down smaller with a little spring pressure to compensate for the extra, "excessive" vacuum. If that is clogged up, more vacuum is allowed to suck than should be. Another way excessive vacuum can occur is from compression braking, again creating a situation that makes the engine suck at the inside of that valve cover. If the drain holes down to the crank case are somehow blocked causing oil to remain in the top of the head, it will want to be sucked out the pvc hose. You need the breather tube side of the valve cover (just to the right of the intake tube) to let fresh air into the valve cover to circulate with the gases from the crank case, if this 1/8" hole is blocked, all you'll have is the relentless vacuum from the pcv hose working against you.
I'd urge you to make sure that part of this air circuit is working correctly and don't do any compression braking at this point. How about a picture of the air intake tube and the valve cover?

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It was suggested to me by one of the veteran techs in my shop, to add some type of restriction to the baffle system. Similar to the old 302 had brillo type baffle under the pcv valve. So I proposed using pieces of industrial scotch-brite pads we use, cut to fit in the baffle walls.

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My ImageShack accout is acting up right now.