porcupine73 Posted June 29, 2007 Share Posted June 29, 2007 You mean like maybe it got scorched? Link to comment Share on other sites More sharing options...
xrturbo Posted June 29, 2007 Share Posted June 29, 2007 Sounds to me like a bad valve. I have also seen valve guides drop on these in two cases but that normally caused massive oil burning. Link to comment Share on other sites More sharing options...
davcoz Posted June 29, 2007 Author Share Posted June 29, 2007 Thanks to all of you for your advise. I'm going to try the compressed air test after I check the timing belt. Still can't figure out how a timing belt could affect one cylinder and not the others. I guess I'm just hoping. The compressed air test will tell me where the problem is. I will let you all know. I've owned six Subarus since 1982. 1982 4wd wagon 126,000 miles, sold in 1987 1985 4wd wagon 278,000 miles, drove to junk yard in 1996 1990 2wd Legacy Wagon 210,000 miles (only automatic I ever owned), gave it away in 2000. 1996 Legacy Outback 180,000 miles, body is excellent, this is the one with the problem. 1998 RS wife's summer only car. Only 30,000 miles, still own it. 2003 Legacy Outback Wagon 54,000 miles, still own it. Link to comment Share on other sites More sharing options...
Cougar Posted June 29, 2007 Share Posted June 29, 2007 Thanks to all of you for your advise. I'm going to try the compressed air test after I check the timing belt. Still can't figure out how a timing belt could affect one cylinder and not the others. The only way I could see it happening is if the other cylinder valves were closed. I think you stated earlier though that the cylinder was making power so a timing belt problem seems to be ruled out in that case. Link to comment Share on other sites More sharing options...
OB99W Posted June 30, 2007 Share Posted June 30, 2007 I'm not going to offer any answers, but I'm going to ask some questions that might be food for thought. [...]The engine started running rough and then cleared up. The next day I drove to work and it ran fine. It started running rough again and the check engine light would blink. It stopped blinking when it started running OK.[...]How many of you have seen a hole in a piston or a burned exhaust valve be intermittent? How does a compression gauge work? Where does what is being compressed come from? What would happen if an intake valve didn't open? Link to comment Share on other sites More sharing options...
nipper Posted June 30, 2007 Share Posted June 30, 2007 I'm not going to offer any answers, but I'm going to ask some questions that might be food for thought. How many of you have seen a hole in a piston or a burned exhaust valve be intermittent? How does a compression gauge work? Where does what is being compressed come from? What would happen if an intake valve didn't open? First you need to understand how an engine works. An engine is a big air pump. http://www.howstuffworks.com/engine.htm Burned valve or a hole in the piston would be zero or low compression. Bad rings would give lower compression. A wet compression test seals the rings. If the number comes up you have bad rings. If they dont come up either the valves are fine, or (if low) you have a worn valve. If the intake valves dont open, you will have no compression. Compression gauge is a pressure gauge with a one way valve in it. Every compression stroke compressed air is pushed into the gauge. It is not unusal to need three or four revs of the engine to get max compression that the cylinder is making. If the cylinder is making 60 psi, no matter how many times you crank, you will only get 60 psi. The same goes for 180 psi (60 120 180 on each crank), this is due to air being a compressable medium, and human error. Burnt valves and holes in pistons are not intermittent. The only thing that may go away is a stuck piston ring. http://www.custompistols.com/cars/articles/compression.htm (its not Always easy to do it on a hot engine,) ANother gauge to use is a vacum gauge, which fills in the rest of the information that a compression gauge may not show http://www.secondchancegarage.com/public/186.cfm hope that helps nipper Link to comment Share on other sites More sharing options...
OB99W Posted June 30, 2007 Share Posted June 30, 2007 First you need to understand how an engine works. An engine is a big air pump.[...] hope that helps Gee, Nipper, thanks for all that good info... ...but I hope you weren't responding to me as if I didn't know the answers to the questions I posed; they were meant to get others to think about alternative theories to the cause of lost compression as measured by the gauge. EDIT: Perhaps I should give up on the subtle approach. Link to comment Share on other sites More sharing options...
nipper Posted June 30, 2007 Share Posted June 30, 2007 Gee, Nipper, thanks for all that good info... ...but I hope you weren't responding to me as if I didn't know the answers to the questions I posed; they were meant to get others to think about alternative theories to the cause of lost compression as measured by the gauge. EDIT: Perhaps I should give up on the subtle approach. Once a thread gets into the third page, i forget who is who nipper Link to comment Share on other sites More sharing options...
Cougar Posted June 30, 2007 Share Posted June 30, 2007 Those last few posts were good. So much for Mechanics Class 102 huh guys. Link to comment Share on other sites More sharing options...
nipper Posted June 30, 2007 Share Posted June 30, 2007 Those last few posts were good. So much for Mechanics Class 102 huh guys. Just wait for 202 nipper Link to comment Share on other sites More sharing options...
idosubaru Posted June 30, 2007 Share Posted June 30, 2007 It is not unusal to need three or four revs of the engine to get max compression that the cylinder is making.] also need a good battery to turn the engine over properly. for example, try turning it over by hand and you won't get good readings (understatement). the FSM relates compression to RPM's...at least the older soobs it does. i know you guys know that, but figured i'd throw it in there. Link to comment Share on other sites More sharing options...
davcoz Posted July 1, 2007 Author Share Posted July 1, 2007 Checked timing belt and it was fine. Ran #1 to TDC and rigged up system to put 60 pounds of air into cylinder. Air came out the exhaust. I removed the rocker arms to get the cam and valve lash adjusters out of the equation. Air still came out of the exhaust, and I mean a lot of air. Valves are no stuck My exhaust valve/valves are shot. Don't understand the intermittant part though. Link to comment Share on other sites More sharing options...
Cougar Posted July 1, 2007 Share Posted July 1, 2007 Sorry to hear the bad news. If the other cylinders are as good as #3, at 180lbs, then it would seem repairing the head will fix things up nicely. I wonder if the intermittent condition was something else happening. Link to comment Share on other sites More sharing options...
OB99W Posted July 2, 2007 Share Posted July 2, 2007 Checked timing belt and it was fine. Ran #1 to TDC and rigged up system to put 60 pounds of air into cylinder. Air came out the exhaust. I removed the rocker arms to get the cam and valve lash adjusters out of the equation. Air still came out of the exhaust, and I mean a lot of air.Not good, but better a head problem than in the block. Valves are no stuck My exhaust valve/valves are shot. Don't understand the intermittant part though.It does seem strange that a valve (or two) could burn that rapidly, but perhaps it was marginal (somewhat leaky, but not that noticable) and you just reached "critical mass". It's likely once you get in there you'll find lots of carbon, which is typically what leads to the valve failure. Link to comment Share on other sites More sharing options...
WoodsWagon Posted July 2, 2007 Share Posted July 2, 2007 I'm getting good at burning the exhuast valves out of my EJ22, so I'll attest to the fact that it's intermittant at first. The engine started burning oil 2,800 miles after it's rebuild. I had drove it from NH to WY 3 days after I put it in, and I couldn't check the oil, so it was down to a quart by the time I got there, mabe less. Way to break in an engine, right:rolleyes: So now it burned oil, not horrendously, but still, a puff of blue now and then. Fast forward to sometime last fall. I'm climbing a long hill, beating on the engine, and it starts missing hard. I downshift and keep it pinned till I get to the top, where I pull over. Miss goes away. I check for broken wires, and spray all the electrical junk under the hood with my water bottle. Miss is still gone. I drive it for the rest of the day, it's fine. Next day on my way to school, starts loosing power, then down to a solid 3cyls. 10psi comp on cyl 3. I replace the head, a couple of weeks later, same thing. Bits of missing here and there, then solid 3cyl action. That was back in december I think? Im still driving it on 3cyls. I think the injector clogged, engough to still fire, but run lean. I had them stored out in the open, and I cleaned and clearcoated the housing with tape over the injector tips, but I may have gotten some clearcoat in the injector tip. (the price you pay for vanity) The rings then got burned, the oil started flowing through, the exhaust valve was hot to start with, and the lean with burning oil sealed it's fate. The easy way to check for the burned valve without opening the hood is putting your finger completely relaxed in front of the exhaust while it's idling. Your finger will be back-sucked into the pipe in time with the junk cyl. I'd replace the whole engine if it was burning any noticible amount of oil. It's really dissapointing to replace the head and have that one get trashed within a month. Link to comment Share on other sites More sharing options...
OB99W Posted July 2, 2007 Share Posted July 2, 2007 [...]The easy way to check for the burned valve without opening the hood is putting your finger completely relaxed in front of the exhaust while it's idling. Your finger will be back-sucked into the pipe in time with the junk cyl.You don't like the "dangle a piece of toilet paper" approach? I'd replace the whole engine if it was burning any noticible amount of oil. It's really dissapointing to replace the head and have that one get trashed within a month.If the rings are gone or the cylinder wall is scored, head work would obviously be a waste of time/money. Unfortunately, it's hard to do a wet-versus-dry compression test (or a leak-down) to check ring sealing when the air's all coming out the exhaust. At this point, pulling the head to examine things is probably the next step, and certainly if any scoring is evident it's probably time to look for an engine. If nothing is obvious in the cylinder, it might be worth a gamble to do the head work. Link to comment Share on other sites More sharing options...
uniberp Posted July 2, 2007 Share Posted July 2, 2007 You don't like the "dangle a piece of toilet paper" approach? If the rings are gone or the cylinder wall is scored, head work would obviously be a waste of time/money. Unfortunately, it's hard to do a wet-versus-dry compression test (or a leak-down) to check ring sealing when the air's all coming out the exhaust. At this point, pulling the head to examine things is probably the next step, and certainly if any scoring is evident it's probably time to look for an engine. If nothing is obvious in the cylinder, it might be worth a gamble to do the head work. Is the first part of replacing heads removal of manifolds? Could a leakdown test be done at that stage by blocking the intake and exhaust ports? If a dual port head, that is? Link to comment Share on other sites More sharing options...
davcoz Posted July 17, 2007 Author Share Posted July 17, 2007 Final Update: Made a friend of mine a deal. If he payed for the parts I'd help him fix the car and I would sign it over to him. We got the head off Friday and one of the exhaust valves was sticking. It was $25.00 to fix the head and $207.00 for the gaskets and belts to put it back together. Can't figure out why the valve would start sticking. That also explains why the problem was intermittent at first. I picked up a 2008 2.5i Outback last week. What a beautiful car. My seventh Subaru since 1982. Thanks to everyone for your help. Link to comment Share on other sites More sharing options...
OB99W Posted July 17, 2007 Share Posted July 17, 2007 [...]We got the head off Friday and one of the exhaust valves was sticking. [...]That also explains why the problem was intermittent at first.[...]Yes, that certainly makes more sense than there being a burned valve. Thanks for getting back with the resolution to the problem, and good luck with the new car. Link to comment Share on other sites More sharing options...
porcupine73 Posted July 17, 2007 Share Posted July 17, 2007 Sounds good and way to help a fellow out! If he payed for the parts I'd help him fix the car and I would sign it over to him.Say...you need any help with that 2008? Link to comment Share on other sites More sharing options...
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