Geoff F Posted August 11, 2020 Share Posted August 11, 2020 Hey all. Last week I started up the soob (2009 Manual Impreza) and heard a light humming coming from the timing belt cover. Turns out that the belt tensioner in the timing belt assembly had slowly backed out of the block and was digging into the cover. I quickly pulled it into the shop before it got any worse and got to work digging into the problem. The tensioner bolt appeared to be stripped so I helicoiled its hole on the block and reinstalled the tensioner with no problems. White marks on crank and both camshafts lined up properly and pin pulled on the belt tensioner. I go to manually spin the crank to check my timing and I hit some kind of blockage at either 1/4 or 1/2 revolution, no matter what camshaft combination I try. I never cranked on it too hard and all 4 spark plugs are out so I know its not compression. I'm scared I somehow bent some valves. The sound appears to be coming from the passenger side of the engine so I took off the valve cover but am unsure of how to check if any valves are bent. I did use the starter and breaker bar to get my harmonic balancer bolt off which I read somewhere on here could be bad. The timing was still on when I did this though so I feel like it shouldn't have caused the issue. Could I have somehow bent my valves or am I doing something stupid?? Appreciate the help. Link to comment Share on other sites More sharing options...
1 Lucky Texan Posted August 11, 2020 Share Posted August 11, 2020 (edited) did you use the dash/groove on the 'tab' at the rear of the crank sprocket - positioned at about 12 o'clock/under the groove/dash on the 'boss' for the cps - for the belt install? some folks mistakenly use the triangle/arrow on the front of the sprocket. That IS TDC, but is never used for belt installation. The line on the 'tab' is used as that puts all the pistons at half-travel position to clear any valve interference. Edited August 11, 2020 by 1 Lucky Texan Link to comment Share on other sites More sharing options...
Geoff F Posted August 11, 2020 Author Share Posted August 11, 2020 I have attached a picture of how my crank is lined up when I try installing the belt. So I see (and am using) the white tab/groove on the front of the sprocket but it also appears that there is another tab on the same tooth on the rear of the sprocket. Is this what you are referring to? Or are you saying I should be using that rear sprocket as my reference and line it at the 12 o'clock position so that there aren't any teeth to the left of the 12 o'clock position when it's properly aligned? Thanks for the quick response. 1 Link to comment Share on other sites More sharing options...
montana tom Posted August 11, 2020 Share Posted August 11, 2020 You are using the correct mark on the crankshaft. You already have the valve cover off . Reach down and try to wiggle the rockers. A bent valve will show as a very loose rocker. Or something fell in a sparkplug hole. Link to comment Share on other sites More sharing options...
montana tom Posted August 11, 2020 Share Posted August 11, 2020 Oh , the tensioner piece you helicoiled is replaceable. Three bolts I think , much safer to replace this than trust a helicoil. Wrecking yard or the dealer , money & time well spent 1 Link to comment Share on other sites More sharing options...
el_freddo Posted August 12, 2020 Share Posted August 12, 2020 @Geoff F - what marks did you use for each cam? Cheers Bennie 1 Link to comment Share on other sites More sharing options...
GeneralDisorder Posted August 12, 2020 Share Posted August 12, 2020 Heli-coil, properly installed, is stronger than the original part. We prefer to heli-coil the tensioner brackets and we do it often. Check valve lash. If the timing is right and the lash is good then very likely there's a very sloppy rod bearing that's about to start making noise. Turning it by hand gets the rod cap bolt hung up on part of the block. I've seen this a few times. They can often run a long time this way but in no way is it a good thing. GD 1 Link to comment Share on other sites More sharing options...
Geoff F Posted August 12, 2020 Author Share Posted August 12, 2020 13 hours ago, el_freddo said: @Geoff F - what marks did you use for each cam? Cheers Bennie Bennie, The driver side cam sprocket is metal with a red painted notch. The passenger side cam sprocket is plastic with a white painted notch. I have both of these at the 12 o'clock position corresponding to the markings on the block/bracket. Link to comment Share on other sites More sharing options...
Geoff F Posted August 12, 2020 Author Share Posted August 12, 2020 8 hours ago, GeneralDisorder said: Heli-coil, properly installed, is stronger than the original part. We prefer to heli-coil the tensioner brackets and we do it often. Check valve lash. If the timing is right and the lash is good then very likely there's a very sloppy rod bearing that's about to start making noise. Turning it by hand gets the rod cap bolt hung up on part of the block. I've seen this a few times. They can often run a long time this way but in no way is it a good thing. GD GD, So you're saying that if the valve lashes are good then this issue is really only due to me turning it over by hand? Could I potentially put it all together and just try giving the thing a start? The engine did not really have a rod knocking sound before this. Link to comment Share on other sites More sharing options...
Geoff F Posted August 12, 2020 Author Share Posted August 12, 2020 15 hours ago, montana tom said: You are using the correct mark on the crankshaft. You already have the valve cover off . Reach down and try to wiggle the rockers. A bent valve will show as a very loose rocker. Or something fell in a sparkplug hole. How much wiggle are we talkin? I count the exhaust rocker on piston 3, one intake valve rocker on piston 3, and one intake valve rocker on piston 1 all barely loose. By loose I mean barely barely wiggling, but not rock solid like some of the other rocker arms. Thank you. Link to comment Share on other sites More sharing options...
GeneralDisorder Posted August 12, 2020 Share Posted August 12, 2020 Rocker arms will all have lash when on the back side of the cam lobe. You will have to put each cylinder in the correct position to check the valve lash. Lash should be about .008" on intake rockers, and .010" on exhaust rockers. And yes - it's likely that if the lash it good it will fire up no problem. But it's probably on it's way out. I bet it knocks when you first start it after an oil change doesn't it? Likely has severely worn rod bearings. GD Link to comment Share on other sites More sharing options...
Geoff F Posted August 12, 2020 Author Share Posted August 12, 2020 3 hours ago, GeneralDisorder said: Rocker arms will all have lash when on the back side of the cam lobe. You will have to put each cylinder in the correct position to check the valve lash. Lash should be about .008" on intake rockers, and .010" on exhaust rockers. And yes - it's likely that if the lash it good it will fire up no problem. But it's probably on it's way out. I bet it knocks when you first start it after an oil change doesn't it? Likely has severely worn rod bearings. GD So from what I understand to get to TDC on cylinder 1, I need to install the timing belt and rotate the crank until the arrow (not the tic mark) on the cam sprocket is pointing to 12 o'clock (passenger side). Only problem with that is that the blockage occurs before I can get to that mark. Any way to get to TDC and the correct cam orientation without having the belt on? Also, from what I can tell .008" has not fit in any of my intake valves. My spark plugs had a lot of gummy deposit on them as well as the boreholes to the plugs. Maybe a valve is just gummed up and stuck open. Link to comment Share on other sites More sharing options...
idosubaru Posted August 12, 2020 Share Posted August 12, 2020 pull off belt and with crank mark lined up rotate cams by hand . Do they rotate? Line up crank and cams and install belt. Verify they still line up after pulling tension. post pics of crank and cam marks to make sure they’re right. Link to comment Share on other sites More sharing options...
Geoff F Posted August 12, 2020 Author Share Posted August 12, 2020 2 hours ago, idosubaru said: pull off belt and with crank mark lined up rotate cams by hand . Do they rotate? Line up crank and cams and install belt. Verify they still line up after pulling tension. post pics of crank and cam marks to make sure they’re right. With crank lined up both cams spin freely, obviously with some resistance with the lobes though. All notches still line up after belt is installed and tensioner pin pulled. I posted a pic of where I'm at. You can see the white tic on the passenger side cam at 12 o'clock, the red tic on the driver side cam at 12 o'clock, and the white tic on the crank at 12 as well. I cannot go clockwise past the red animated dash nor can I go counterclockwise past the blue animated dash. I know I shouldn't roll it counterclockwise but it just happened. Can the cams be 180 degrees out of phase with the crank? I keep hearing the blockage sound like its coming from one of the valves on piston one but I have no idea how it would have gotten bent. Lastly, the timing belt I am using did make contact with itself while the tensioner backed out in the first place. The belt pretty much looks undamaged visually aside from a small amount of hardly worn down grooves. Do you think this could be enough to heat up the belt and cause it to expand? Thanks again for all your help. Link to comment Share on other sites More sharing options...
GeneralDisorder Posted August 13, 2020 Share Posted August 13, 2020 (edited) Even if all the valves (or just one) were bent, they wouldn't hit the piston once it's properly timed. They close they just don't seat. Also this would show as extremely excessive lash (like 1/4" of it). I've already explained what is most likely going on with your engine. It's dying. As the rod cap reaches bottom dead center it's hitting the block casting. Probably the #2 rod is hitting between the cylinder liners on #1/3 GD Edited August 13, 2020 by GeneralDisorder Link to comment Share on other sites More sharing options...
Geoff F Posted August 13, 2020 Author Share Posted August 13, 2020 36 minutes ago, GeneralDisorder said: Even if all the valves (or just one) were bent, they wouldn't hit the piston once it's properly timed. The close they just don't seat. Also this would show as extremely excessive lash (like 1/4" of it). I've already explained what is most likely going on with your engine. It's dying. As the rod cap reaches bottom dead center it's hitting the block casting. Probably the #2 rod is hitting between the cylinder liners on #1/3 GD I appreciate all your help GD. It's just hard for me to believe because this is a JDM engine that I dropped in the car only about 3,000 miles ago. They claimed it had only 45,000 miles on it which I thought was well before the typical time it takes for that rod knocking to develop. The plan now is to adjust the lash on all my valves, throw everything back together, and see if she runs. I'll keep ya posted. Link to comment Share on other sites More sharing options...
GeneralDisorder Posted August 13, 2020 Share Posted August 13, 2020 The JDM engine suppliers always say something like "40 - 60k miles". What they don't tell you is that is an average and the older the vehicle the less likely that is to be true. They have no idea what the mileage of any specific engine is - they don't get that information and even if they did it isn't likely to be true because the scrap yards in Japan will just make up numbers and send pictures of whatever odometer they have laying around to appease the buyers. Also - JDM engines are a doubled edged sword. Yes they may have low mileage - but it's a cultural thing not a "law" as some believe and some people in Japan don't do any significant maintenance because they know they will get a new one in a few years. Also they tend to be short tripped a lot and that's really hard on the engines. Subaru's have exceptionally tight main bearing clearances due to their aluminium block design and so require careful warm up and maintenance. As with many things - you get good ones and bad ones. I have seen plenty of both. Usually heavier on the good side but I have sent engines back because they were UGLY inside and I didn't want to run them. GD Link to comment Share on other sites More sharing options...
Geoff F Posted August 18, 2020 Author Share Posted August 18, 2020 Quick update: I didn't have the balls to put it all together and try starting it. I did try cranking pretty hard on the crank with a breaker bar with the timing belt all assembled in the hopes that something (not a valve) would break loose but no dice. While adjusting the lash on the passenger side, my buddy and I ran into a problem with the exhaust valves on cylinder #1. No matter how far we loosened the nuts on the rocker arms, the lash would not change. The springs would just keep decompressing further and further. I took the valve cover off on the driver side and confirmed that cylinders 2 and 4 have proper play in the exhaust valves but cylinder 1 is rock solid (3 has normal movement as well). It appears likely that these valves are bent or broken off. My only question is how in the hell that happened from the time I pulled the functioning car into my shop to now. Gonna be a real shame if I have to do ANOTHER engine swap. Link to comment Share on other sites More sharing options...
el_freddo Posted August 18, 2020 Share Posted August 18, 2020 Every time you check a cylinder for valve lash, best practice is to rotate the engine until that cylinder is at top dead centre. This ensures the cam follower is not being acted upon by the cam lobe. To me it sounds like you had cylinder 3 at or near TDC, sorted it properly then immediately went to cylinder 1 to do the same, but the exhaust valves are under tension from the cam lobe acting upon them. Re-read the procedure and try again. Cheers Bennie Link to comment Share on other sites More sharing options...
Geoff F Posted August 21, 2020 Author Share Posted August 21, 2020 (edited) Well folks, the verdict is out. I decided to take the engine out of the car and it is just as I suspected. After taking the exhaust manifold off during the removal process, I peaked my head up into the exhaust channels of cylinder one and sure enough all I saw were two cracked stems. Got the engine out and pulled off the head and there were the two heads of the valves just laying in the cylinder as if someone just placed them there. Two fresh carbon imprints on the piston head from where they collided but otherwise a completely undamaged head, cylinder, and piston head. My guess as to what happened is as I used the starter/breaker bar to remove the harmonic balancer bolt, the relatively loose timing belt (because of the failing tensioner bolt/thread) skipped a few cogs and smashed the piston head into the exhaust valves, snapping them perfectly in a split second. This must be the case because if it had happened at any other time I surely would have heard the valves getting mauled in the cylinder and they would be severley damaged. I had barely even turned the ignition when using the starter yet it was enough to do the damage. So, aside from the two exhaust valves on cylinder one, the engine is in complete working order. Any recommendations as to where to go from here? My game plan was simply to order a set of exhaust valves and begin the re-installation process. Best place to order em? Any qualms with this? Thanks guys. Edited August 21, 2020 by Geoff F additional question Link to comment Share on other sites More sharing options...
montana tom Posted August 21, 2020 Share Posted August 21, 2020 Pay a little more and buy a japan made or a US made valves. Avoid the china made . Use subaru # 642 mls head gaskets Link to comment Share on other sites More sharing options...
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