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So has anyone actually fixed the oil puking out of the PCV?; Tons of posts on what it could be, no posts about the actual result?
Topic Started: Dec 29 2011, 10:27 AM (4,275 Views)
merlot566jka
Engineer
[ *  * ]
So I have been reading through the posts where people have similar problems to mine. Oil pumping out of the valve cover into the pcv vent and into the air cleaner. This seems to be a very common problem.

Peoples suggestions:

Re-Ring the engine
Use head gaskets with bigger oil holes
make sure oil restrictor valve is installed in block
clean out pcv tube
replace pcv
adapt a catch can
check the oil level

Peoples results:
????

I have re-ringed the engine. New pistons, honed the block.
I have not used the larger hole gaskets yet, but the smaller hole gaskets are the same as factory, and those holes are not for oil drain back, they are for crank case gases.
Oil restrictor is in block.
PCV tube is clean and clear
PCV is brand new
Catch can has been adapted, about 1/2 qt went into the catch can. and lots of moisture (typical witha catch can)
Oil level after 250miles was at the add line. Still golden clear (indication that there isnt an abundace of blowby)

My results have been that there is still a lot of oil coming out of the valve cover. The engine runs great, no smoking, plugs are clean and compression is 150 +- 5% on all 3 cyl. The catch can is catching all of the oil that is being pumped through the tube.

So the last test I did was to check for excessive blow by, I removed the hose on the outlet of the valve cover. There is tons of air pumping out at idle. The air, does not smell like burnt or un burnt fuel. This leads me to several questions.

Is this normal?
If its not blowing by the rings, why is so much air pumping out?
How are other engines designed to deal with crank case gases?
Is this an inherent design flaw?
How have other people solved this problem?
Has anyone ever actually solved this issue?
Why is this happening?

Is this normal?
Well yes. If the rings are sealing off the combustion gases, then in theory we are moving around 993cc's of air per revolution in the crank case. BUT WAIT, THERE IS MORE!! In order to pump air, there has to be an inlet and outlet. So how does air get in and out of the crank case? Well we know it gets out through the valve cover vent... but where is it coming in? If the rings were leaking (beyond normal), then the air would be coming from the combustion chamber. The oil would turn black quickly and the oil would smell of burnt fuel or fresh fuel. But the oil is blatenly clean, and smells like oil. So where is the air coming from? Well like a 2cycle engine, we could be puming out and drawing air in through the same hole. That would mean air is fluctuating between negative and positive on the PCV outlet. This could cause a slew of problems. The other posibilities is that air is drawn in through leaking seals, or that air is drawn in though the dipstick tube.
How are other engines designed in respect to thier PCV systems?
Well this obviosly varries greatly. There are open and closed PCV systems, ours is a "closed" system because it draws in fesh air from the air cleaner, expells it into the crank case, and then those gases are drawn into the intake tract when they become positive, or there is a vacuum on the intake.
WAIT A MINUET.... yes, a pcv system is designed to draw fresh air in and expell combustion bypass. So we ARE infact pumping air out and in through the same tube. I wonder if other engines do the same thing???
Most of my automotive expierence and research has been on V engines. All of the ones I have been in have a breather on one valve cover (either vented to atmosphere or to the intake tract BEFORE the throttle body) and the other one goes to the actual PCV. The PCV is located both in the valve covers or the intake manifold. With this style of setup, its easy to see that one side would draw in fresh air, pump it through the crank case and then into the other valve cover where it is then drawn into the intake manifold when it is under vacuum.
So how is it done on other inline engines? The only inline engine I have is a big 7.8l Multifuel military truck, and it has a road draft tube. So I dont ahve any personal reference. On google, looking at other 4 cyl and inline engines I see that their systems are different than out own. Look: http://z.about.com/d/autorepair/1/0/-/P/accord_pcv_657b.gif
http://ww2.justanswer.com/uploads/supermechanic/2011-01-21_200026_pcv_valve.gif
http://www.harleyc.com/prelude/faq/imgs/pcv.gif
http://www.brakeandfrontend.com/Content/Site308/Articles/03_01_2009/94126pcv1LOjpg_0000004787
http://t1.gstatic.com/images?q=tbn:ANd9GcROyaPYmboInv6m3vodamhI2kN7Y7li0sYFrX_uiXWhRC3N2YmU
http://t2.gstatic.com/images?q=tbn:ANd9GcRJ_WYvLJHOkqRQefUx856Q9KwPIA-H0XkvCorvIJfdiImaqT6I2g
These illustrate that most engines have a seperate inlet for fresh air, and an outlet for PCV.
Ok, so do any other engines have the same we do? YES:
subuaru justy (3cyl) http://www.dustysjustys.com/images/cars/service_pcv_system.jpg
well, thats the only one I could find... but I am sure that someone has the same singe PCV tube... with both an inlet and outlet.
So it appears that other engines deal with PCV differently than the G10. Is ours inferrior? Is there a benifit doing it another way?


MORE TO COME, AT WORK, kinda have to work now.

an hour or so later...
I can see that the other engines are infact designed different. Most have two seperate ports for intake of fresh air and outlet to PCV. Some have the crank case directly vented. But still, this style (the G10) is used on other engines. So it is not flawed perse... but are there better ways of doing it? Probably.


Which leads me all the way around to:

Did it burn oil from the factory out of the crankcase breather?
Edited by merlot566jka, Dec 29 2011, 11:36 AM.
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99metro
putt-putt

55 mph+ I was leaving a smoke screen. This lasted about a year before I got tired of it. I even had my crank seal blow out on me (fun). I did fix it. New PCV and I re-ringed the engine. Now I can drive 70+ mph without blowing oil. It's not too much more complicated than that.

My temporary solution before I re-ringed was to lift the dip stick up about an inch or so to allow excessive crankcase pressure to be released.
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merlot566jka
Engineer
[ *  * ]
99metro
Dec 29 2011, 10:59 AM
55 mph+ I was leaving a smoke screen. This lasted about a year before I got tired of it. I even had my crank seal blow out on me (fun). I did fix it. New PCV and I re-ringed the engine. Now I can drive 70+ mph without blowing oil. It's not too much more complicated than that.

My temporary solution before I re-ringed was to lift the dip stick up about an inch or so to allow excessive crankcase pressure to be released.
STD pistons and rings?
did you use the updated head gasket with lager holes?
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sphenicie


just my 2 cents, i spent alot of time ice fishing last winter and there was very little sno on the ice so i drove the geo, i sucked alot of sno in the air intake, unknowingly, when the car sat over night the water in the pcv froze and out popped the cam seal.
if pressure builds up inside the engine, it will push out oil, any where, easiest places first, and then that internal pressure WILL blow out a seal. I always like to look at the easyiest, cheapest, fixes first. good luck, hope its something easy.
.
another thought; when you did the rings, did you mic the cyl's? honing will almost never true a cyl. most machine shops ( around here anyway) charge 12-15 bucks a hole. what did the rings cost? pressure is getting out somewhere. out of round cyl? OK call it 3 cents. let me know when you solve it.
Edited by sphenicie, Dec 29 2011, 12:24 PM.
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merlot566jka
Engineer
[ *  * ]
I mic'ed the top and bottom, I dont have a bore gauge, just a few digital micrometers. They were both under 73.93 on all three cyl. This was done at about 1/2 and 1" into the bores. The results were the same after honing as well.
I obviouslt couldnt check the cyl to see if it was out of round or not with this method.

the rings were from Parts Dinosaur http://www.store.partsdinosaur.com/product54.html

The pistons were from Parts Dinosaur as well http://www.store.partsdinosaur.com/product3610.html

the bore brush: http://www.amazon.com/dp/B002XUL0X6/ref=pe_175190_21431760_cs_sce_dp_2
Edited by merlot566jka, Dec 29 2011, 01:10 PM.
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Shinrin
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My engine was done by a crappy mechanic so I don't know parts or anything he used. New rings I know, dropped off at a machine shop I know. Blew oil upon return. Replaced the check valve and a new head gasket(which did not have enlarged holes) and all was good. Not all, but no more blow by. I had a catch can setup for awhile, would take a quart every few hundred miles. Leaks a little oil now, maybe 1 quart per 1000 miles from my cam or crank seal.
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dayle1960
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Fastest Hampster EVER

I've never had a problem with my pcv in ten years of ownership. I've done two rebuilds on the engine and only cleaned out the y tube. I did have an oil fart about five years ago but it lasted all of a quarter mile. Haven't even looked at the y tube in over two years. No runs, no leaks, seals are still good.

Maybe you just got a case of bad mojo hanging over your metro. Either a metro owner learns to live with the quirkyness of these cars or he will be chasing his tail for a long long time.
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starscream5000
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Got 70 MPG?

Never seen this issue with any of my Geos either. It's only an issue for those who don't take care of the car properly.
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clarkdw


I went through the same agony when building large overbore race engines on old Mini Coopers. No venting on the sump of the engine. Only the small vent on the valve cover like the G10. I could not keep oil in the engine till the cylinders sealed up. It would fill the valve cover.

My assessment is this: You are getting excessive blowby on the rings and it is causing your problem. This is fairly certain.
Suggestions are: If you think that the cylinders are reasonably round and the rings will eventually seal up use the catch can as a stop gap till it seals up. Not likely the right answer but may get you through the next little while.
Second suggestion: Don't use a berry hone. They make a lovely looking finish on the bore but do absolutely nothing to show any ridges or out of roundness. They should only be used for rering jobs where the roundness and straightness of the bore is a known.

Third: Get a set of telescoping guages. They are very cheap and used in combination with a digital vernier can tell you a lot. I suspect you will find taper or out of round in the cylinders in which case the answer is oversize pistons and rings.

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Lincoln
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Member
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I started having the same problem a while back. I noticed the problem got worse when traveling above 70 mph (higher RPMs). I installed a catch can and that is a band aid fix. As long as I keep the RPMs down my catch can stays pretty empty. My compression is about the same as yours and the consensus was I needed a rebuild, which is coming in the near future.
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sphenicie


your bore can be off in many different ways. out of round, generally longer perp to the crank. also differences top to bottom, ice cream cone, or hour glass, or the reverse of each. i agree with Clarkdw, the pressure is coming from the cylinders. if you are going to put the effort into it, get the holes bored. a good machine shop will not take off more than needed, and even with the cost of pistons, your time is not waisted. i am sure one of us could help you find a cheap block to prep, so you can keep running while you get it together. further, i think you said the compression was 150, keep in mind, that is 25% low!

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obaja
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Diesel Power

Your compression is almost shot. Should be 200 with warm engine throttle wide open.
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Old Man


Lincoln--sphenicie--obaja
Try reading the complete thread---he has just done a re-ring and the rings have not set in yet
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redpepe


hi merlot,

for what it's worth, and while you may have different problems, replacing the head gasket with a modified one [enlarged holes] cured the oil fogging problem on mine. that was right after the rebuild at 325k. hasn't had a problem since and yes my original head gasket had small holes and never had the fogging issue. it remains an inadequately explained contradiction ... original small holed gasket never fogged ... but the larger holes 'cured' the condition.
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sphenicie


i have NEVER, EVER, had a fresh engine, with bored holes push that kinda pressure, popping out seals, and "pukn" oil. i certianly hope its just that the rings havent seated. i have the machine shop bill in hand, "bore + clean block" (includeing dusting the head deck)=$45. "polish crank"=$25. "resurface head"=$32.50. date=9/14/11 I have not had any such issues. Ive done plenty of quicky "in the car", rebuilds that have. I no longer put the time into pulling an engine apart just to be disappointed. my advice, for what its worth.............save up the $102. I am sure it will be a cure. The only issue ive had is it runs to cool in cold weather. hope i am wrong!
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