RallyKeith Posted January 7, 2006 Share Posted January 7, 2006 So, this was mt original post: I've got a EJ25 DOHC motor that is burning on the order of 1 quart every 100-150 miles. When driving it you do not really notice any smoke out the back, until you coast down a hill. If you are up to speed (40-50 mph) and you coast down a long or hill for something like 1/8 mile, and get back on the gas a big cloud of smoke erupts from the tailpipe. Now everything I know tells me that this is valve guide seals, but I wanted some other input before I go tearing apart the motor. Thanks, Keith I have since done a compression test both dry and wet and found no problems. AND I've since replaced the PCV valve, with no change in the burning rate. THIS IS IMPORTANT. So, I decided it must be a mix-up in the valve guide seals by the machine shop that rebuilt the heads for the person I bought the engine from, and started today to swap on my known good heads. Here is the good stuff: I pulled the intake manifold off to find oil running down the inside of the intake runners, and oil pooled up on the intake valves!!! Now I'm baffled. I replaced the PCV valve with a brand new one from the dealer, all the hoses were clear, and everything is hooked up correctly. What could be the problem? I did notice that as I was taking the intake tube off with the breather hoses for the valve covers, that what seemed like water ran out of the one. Could there be something wrong in that breather mechanism of the valve cover that is letting the oil through? HELP Oh, and thanks for all the input. Keith Quote Link to comment Share on other sites More sharing options...
cookie Posted January 7, 2006 Share Posted January 7, 2006 Man that sure would put oil past the valves like seals. You ought to be able to test the pcv valve by sucking on it. It sounds like you are getting oil into that intake for sure. I can't think of any reason unless you mixed up a hose. As far as I know the pcv valve should seal the crankcase from the manifold. Quote Link to comment Share on other sites More sharing options...
blitz Posted January 7, 2006 Share Posted January 7, 2006 Keith, I agree with Cookie. I just can't see any way for such a large amount of oil to find it's way up into the intake manifold unless one of the PCV hoses or couplings are completely blocked or mis-routed. I'll confess that I've never understood what is the purpose of the center hose coming off the airbox going to the "T" fitting. Quote Link to comment Share on other sites More sharing options...
tunered Posted January 8, 2006 Share Posted January 8, 2006 could this be serious case of blowby? Quote Link to comment Share on other sites More sharing options...
blitz Posted January 8, 2006 Share Posted January 8, 2006 Just had another thought: Maybe the the dipstick is reading wrong and the crankcase is overfilled. The PCV valve would suck all the whipped-up oil mist out of the crankcase and straight into the plenum. Quote Link to comment Share on other sites More sharing options...
edrach Posted January 8, 2006 Share Posted January 8, 2006 My '91 legacy had a very similar problem but caused by serious blow-by. In my case it would exhaust vast quantities of smoke for the first 4 or 5 minutes of running and then all would be okay. Until last weekend when the smoke wouldn't stop and I finally parked it rather than severely damage the engine more than it was already. Throttle intake hose was dripping with oil when I replaced the engine today as well as most of the hoses feeding it. Quote Link to comment Share on other sites More sharing options...
cookie Posted January 8, 2006 Share Posted January 8, 2006 That's usually east to spot if its blowby. You remove the PCV valve and they smoke from the crankcase like mad. Or for that matter ofen if you open the oil filler. Interesting problem. Quote Link to comment Share on other sites More sharing options...
edrach Posted January 8, 2006 Share Posted January 8, 2006 That's usually east to spot if its blowby. You remove the PCV valve and they smoke from the crankcase like mad. Or for that matter ofen if you open the oil filler. Interesting problem. In my case the blowby was so bad that if you unscrewed the oil filler cap and just put it back without screwing it on it would blow off. Quote Link to comment Share on other sites More sharing options...
RallyKeith Posted January 8, 2006 Author Share Posted January 8, 2006 Let me address all the issues in one reply. As for the PCV valve, unless the brand new one from the dealership that I installed went bad from the time I screwed it in to the time I first started the car I can't imagine that it is the problem, but hey I check it again As for the dipstick reading wrong, my owner's manual says it takes 4.7 us quarts of oil, and both times I've changed the oil while it's has this problem it has taken just under 5 quarts to get it to read full on the dipstick. I will double chech that though tomorrow. By blow by we are talking blow-by the rings correct? I did a compression test and had numbers all right around 190 psi give or take 10. Also, if it was that serious of blow by I would expect the dip stick to be pushed out of the holder from all the pressure and it is not. So the theory is that something is causing a major build up of pressure in the crankcase that is pushing oil somehow through a breather and into the intake manifold? Oil in the intake tube... As I'm thinking about this, I don't remember seeing anything I didn't have much time to analyze things in depth after I pulled the intake, so first thing sunday afternoon I'll dig into some of these things. Keith Quote Link to comment Share on other sites More sharing options...
RallyKeith Posted January 8, 2006 Author Share Posted January 8, 2006 Just another thought... I'm going to see if I can find a diagram of how the PCV hoses are run. Maybe one got swapped on that T. I think each side of the T goes to the valve cover breathers, and then the other connectionn goes into the T for the Crank Vent before the PCV valve. Keith Quote Link to comment Share on other sites More sharing options...
rallynutdon Posted January 9, 2006 Share Posted January 9, 2006 Today we found there's no oil in the intake prior to the throttle body. There seems to be no difference in the air movement of the filler tube with the cap off comparing it to another motor (2.2) that's in good condition, at idle or at 2-3000 RPM. Even if the was an issue with the oil control rings I would think the other rings would have to be in real bad condition (hence low compression) to cause blowby and significant oil consumption. Quote Link to comment Share on other sites More sharing options...
RallyKeith Posted January 9, 2006 Author Share Posted January 9, 2006 Today we found there's no oil in the intake prior to the throttle body. There seems to be no difference in the air movement of the filler tube with the cap off comparing it to another motor (2.2) that's in good condition, at idle or at 2-3000 RPM. Even if the was an issue with the oil control rings I would think the other rings would have to be in real bad condition (hence low compression) to cause blowby and significant oil consumption. Yup, like he said... Nothing seems to add up. I can't figure out what we are missing. Quote Link to comment Share on other sites More sharing options...
tunered Posted January 9, 2006 Share Posted January 9, 2006 to get a fair reading on blowby you need to block off the pcv,if its not puffing out the oil fill tube with the pcv blocked its not blowby,if thats not it the engine cant be breathing,air has to go into that block from somewhere,not sure where but we need to find out because something is blocked off. PS blowby will be at its worst at idle. Quote Link to comment Share on other sites More sharing options...
RallyKeith Posted January 15, 2006 Author Share Posted January 15, 2006 UPDATE 1-14-06 We ran a leak down test on the engine friday night to try and determine if there was indeed a ring problem. We got a maximum of 6% on any of the cylinders. For a motor with 95k that sure seems good to me. We then tested the motor I took out of the car with 185k that was not burning oil and the LOWEST we got was 30% So we still have NO clue as to what's going on. The only thought I've had is if there could be a slight blockage in the oil return from one of the heads that is causing excess oil to pool up near where the vents are in the rocker cover. As soon as I get some time I'm going to look into it but other than that I have no clue. Keith Quote Link to comment Share on other sites More sharing options...
1 Lucky Texan Posted January 15, 2006 Share Posted January 15, 2006 I forgot if this is a turbo or not. maybe the turbo oil seals are bad? I dunno Quote Link to comment Share on other sites More sharing options...
Scoobaroo Posted January 15, 2006 Share Posted January 15, 2006 A compression test and leakdown test isn't really an oil ring test; it's a compression ring test. My bet is that the oil control rings are either stuck or worn. There's no way that a quart per 150 miles is getting past the valve seals. Excess oil on the cylinder walls due to bad oil rings would actually INCREASE your compression readings and reduce leakdown on a static level. Even an engine with no valve seals at all wouldn't burn that much. I see an engine overhaul / replacement in your future. Quote Link to comment Share on other sites More sharing options...
ferret Posted January 15, 2006 Share Posted January 15, 2006 I think you have all PCV hoses hooked to an intake vacuum which would do give you the condition you have. Oil all in the intake. Still could be the Oil rings. I have seen compression good on all cylinders and 1 cracked oil ring causing very high consumption. Remember this is their job. Here's a quick crankcase ventilation overview: Fresh air > Filter it (subaru takes fresh air after the air filter) > into valve covers (usually into both covers) > purges crankcase of fumes > exit at top rear of block just above oil seperator plate > into intake thru PCV valve to be burned with the fuel. Now to the exceptions....Since there is engine vacuum, that lower pressure will keep the flow as described above. However at Wide Open Throttle, vacuum at the intake is low or non-existant. So they put a Y here to allow flow either way into the intake or airbox. Without fresh air in the crankcase, the pressure builds, and forces oil out anywhere it can, backward thru the PCV system into the intake hose (as is the case with a stuck closed PCV valve), or give you blowby on the rings. PCV stuck open....all works well.....unless you have an engine backfire...Thats when the PCV valve is a lifesaver. With a mixture of fresh air and oil fumes, a spark or flame coming in thru the PCV line is disasterous.....saw the remains of that once back in 67 or 68. Quote Link to comment Share on other sites More sharing options...
RallyKeith Posted January 15, 2006 Author Share Posted January 15, 2006 Excess oil on the cylinder walls due to bad oil rings would actually INCREASE your compression readings and reduce leakdown on a static level. Good point. When we did our compression test we did it first "dry" and then we squirted some 5w30 in each cylinder and did it again. The numbeers went up, so it makes me want to bellieve that this really isn't the case. I wold have expected the numbers to not change. Keith Quote Link to comment Share on other sites More sharing options...
frag Posted January 15, 2006 Share Posted January 15, 2006 In case the following could help. A few months ago, I checked the vacuum just to see how the engine was doing generaly. The readings I got were perfect but when I got the vac gauge hose plastic tip out of the right rear intake plenum opening (there is a little plug there), it was dripping with oil. I dont have smoke coming from the tail pipe and my engine (near 150,000 miles) does'nt burn too much oil (around a littre for 5,000 kilometers, part of it being due to some slow leaks). Also,my PCV valve is OK and I have no reason to think that anything is connected wrong. Quote Link to comment Share on other sites More sharing options...
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