Why Subaru Engines FAIL

Today we're going to be tearing down this Subaru engine to find out what's inside and how it works. We're also going to be taking a look at some of the common failure points in this engine to look out for when buying a used Subaru. And here we've got Subaru's common EJ25 engine. This is a 2.5 liter four-cylinder horizontally opposed engine so the pistons actually move sideways. That's why the engine looks so wide. This engine did come in different variations including turbocharged and dual overhead cam with variable valve time. Now one of the common issues you'll see with the engines is they knock on your door so they go knock knock and when you answer your connecting rod comes out. So we're going to tear into this scrap engine just to see how everything's laid out and what's inside and perhaps do something interesting with it when we're done. Now because this is a boxer engine we have two pistons that move sideways inside of this half of the block and another two pistons that sit on this side here. We have the two engine heads that sit on either side to each other with the intake going from the top here and the exhaust coming out the bottom here. We have the camshaft located over here for each head and the crank in the middle here at the back here is where the transmission is going to locate. Now this engine because it's so wide sits very low in the engine bay and it's situated longitudinally so it's kind of set up like a rear-wheel drive car. So here we have an EJ253 engine inside the vehicle just to show you how things are situated. Looking over here on the driver's side you can see we have the front timing cover and the accessory belts. Now this is pretty easy to service on this vehicle however we do have one of the heads on this side here and a disadvantage of having the head so close to the frame rail you can see here is clearance to access things like your spark plugs. Here's one spark plug here and the other one is way at the back here and you can see the situation is similar over here on the passenger side we have the head over here the spark plugs are located in behind this air box so servicing this engine in terms of that aspect is not that easy. Now this engine is driven off of a timing belt you can see you've got the crankshaft in the middle and the two cams on the outside here we have the water pump here then we have three idler pulleys and then a tensioner so we'll just go ahead and start peeling this timing belt off this is a really long timing belt just because the engine is so wide. I'm going to start working on one head at a time so I'm going to rotate this engine here just remove the valve cover itself now because this is the single overhead cam version of this engine it has a single camshaft that runs down the center underneath here and that's driven off of the timing belt here we have the rocker arms that rotate against this pivot shaft here and here we have the exhaust side on this side here and the intake side over on this side along with the spark plugs so you can see as I rotate the camshaft back and forth here just how this rocker arm pivots to push those valves down and open them into the engine. Now I'm going to remove all the 12 millimeter bolts that hold this rocker assembly to the head now I'll just remove this rocker assembly for the intake side and then remove the exhaust rocker assembly and with the rockers out of the way you can see how the camshaft rotates now a common issue with the newer engines is they have an internal hex that tends to strip out luckily mine is just a 17 mil bolt and I'll just stick a screwdriver in there then I can remove the cam gear and pop off that timing cover now because this engine does not have variable valve timing you only have one cam sensor over here the other head does not have a cam sensor and next up we come to another potential issue on this engine and that's the head bolts some people say that these need to be retorqued after a certain mileage and that'll prevent the head gasket issues now I've already loosened these up it's a 14 millimeter 12 point bolt you'll also notice that the two middle ones here have black tops and that's because they get tightened a little bit tighter than the other three and now I'm going to separate the head from the block and here we come to one of the most common issues with Subaru engines and that's that these head gaskets fail now a lot of people like to blame the head gaskets themselves because the original ones were made of a composite like material and when one of those layers were compromised it would cause the engine oil coming through the oil gallery here or the returns here to mix with the coolant inside of the water jacket over here now when coolant and oil mix they don't necessarily do each other's job properly the coolant is not really good at lubricating and the oil is not really good at cooling the engine therefore either the engine itself overheats or you run out of oil and lose lubrication to the pistons moving up and down now sometimes these engines have an external head gasket leak where coolant leaks outside the engine and you could see a little bit of a leak coming from underneath the engine now here we've got the pistons on this side of the engine and you can see that they are 180 degrees out of phase from each other and that means that on the opposite side of the engine you have these on the opposite side of the phase which is great because this engine is really well balanced and counteracts any secondary acceleration forces so for a four-cylinder this engine shouldn't vibrate nearly as much as an inline side of engine now for a 2.5 liter four-cylinder engine the diameter of these pistons are pretty large and that's because it's an over square design where the pistons themselves have a larger diameter than the stroke an over square engine design is good because it's going to give you less shaking forces in the stroke direction and it's also going to develop power at a little bit higher rpm which is why these engines are popular with tuners and people who are doing rally races now the real reason why a short stroke is used is because of packaging because the engine is so wide and sits horizontally it dictates the size of the engine bay so if you go any longer on the stroke your engine's going to become wider and it's going to limit some of the suspension geometry on the vehicle i'm just going to remove all the 14 millimeter bolts that hold the idler pulleys on on the timing side of the engine just quickly remove the cam cover on this side and the cam bolt and we'll take off all the head bolts and i'll remove the head this here's where the oil filter lives i'm going to remove the oil pan bolts you can see it's looking kind of sludgy inside of there there's evidence here that either the oil was sludging up or it was mixed with coolant at some point now the oil pan and pickup tube remove you can see we have clear access to the crankshaft that rotates inside of this block here now this engine block here splits into two halves in order to get the crankshaft out now one other flaw on the subaru engines is oil starvation now i don't have the pickup tube but it would normally sit up here at the bottom of the sump and suck oil down into the inlet for the oil pump it's going to then pressurize that oil and send it out to the heads as well as the main bearings and the connecting rod bearings on the crankshaft now one problem that could arise is if you run low on oil your bearings are not going to get really well lubricated and then that's going to cause them to heat up and wear out causing these marks that you see on this crankshaft as well as on this connecting rod they're then going to lose their tolerance between each other and then it's going to start knocking back and forth now this problem is attenuated with subaru's oil burning problem and that's to do with this oil control ring you can see at the top two here we have the compression rings and here we have the oil control ring that's supposed to scrape the oil away from the inside of the cylinder and keep it in this section over here in the sump rather than putting it on the combustion side where it can get burned however in some cases you can see how thin this oil control ring is it can get clogged up with sludge and these return holes here can also get clogged up therefore instead of the oil returning back through the piston skirts and falling back down into the sump it ends up in the combustion chamber getting burnt and then you run out of oil now a boxer engine makes this even worse because it's horizontally opposed and gravity isn't exactly helping you to retain any of that oil that you're pumping out from the sump you can see subaru's tried to add baffles inside of here as well as shape the oil pan down into a point here where the oil pickup tube would be that way if you're taking a rally course and you're moving from side to side there's less a chance of the oil pump just sucking up air instead of oil i'm just going to remove all the 10 millimeter bolts that hold the oil pump onto the crank and we could just pry that oil pump off and there's the oil pump now we're going to remove the water pump and the water inlet assembly now gravity doesn't exactly help the head gasket situation either when the car is parked all of its fluids are just going to kind of stop right here at the bottom of where the head gasket is and if those fluids like the coolant or the engine oil is contaminated it could start to eat through the head gasket and cause a leak now as we've already seen this engine is pretty weird and what's even weirder now is that we need to remove this connecting rod pin here to get the piston heads off of the connecting rod in order to split the block and take out the crankshaft now in order to get access to that connecting rod pin you need to open up these access ports over here it's a 14 millimeter hack now if you haven't got a 14 millimeter hex you could just take a 14 millimeter head bolt thread two nuts on the back and put a wrench in the middle and this is your 14 millimeter hex that you insert into here and you can loosen off that plug turn the crank to align the piston to line up with this hole maybe a little difficult to see but that's the connecting rod pin lined up there i'm just reaching with these pliers here and then i can pull it out now to get the pin out you'd have to either push it out from the other side or you can get a special tool that has a hook on it now in order to get access to the access holes on this side here i'm going to have to remove this engine from its engine stand but before i do that i'm going to try to break all the bolts free to split this block in half now this engine block's got quite a few bolts going around it and inside of it holding it together you can see there's five obvious ones here across the top over here there's another two and then another one hiding up here now inside the water jacket themselves there's also some bolts hiding inside of here there's even more bolts hiding inside of there it's really long and there's one more bolt over here on the oil pan and one at the back here so with the engine block removed from the stand we have this access port at the back here and from here you can see the other connecting rod pin what we're going to do is take a small rod and just catch it just like that i'm going to back off from the crank and you'll see that the piston is now stuck in its spot and we'll try rotating the piston i can lift up the connecting rod and you can pop it through the block now another weak spot on some of the subaru engines was piston slap and that's because of the tolerance around this piston skirt here was eating up pretty quickly and the teflon coating wore away and that allowed a little bit of wiggle as the piston moves down and up its shaft now as it wiggles it's going to make a little bit of a clatter especially on cold starts and that's what's called piston slap it'll go away when the engine warms up i wonder if i could separate this block since on this side all right so that's one half here here's the rear main seal and because the pistons can't come up through the block this way i'm going to remove them down this way by disconnecting the connecting rod here at the crankshaft you can pull the piston out this way suddenly everything got so oily so i'm just going to use what's left of my brother's old sock here and wipe off all the oil residue and you can see we've got our boxer engine all taken apart here now taking a look at those connecting rod bearings you can see they are absolutely chewed up and you can tell that this engine has run low on oil at some point and when there's no lubrication on these bearings they just start eating themselves up and that's what causes connecting rod now so here we've got the main bearing and you can tell it also has been starved of oil it's got a lot of sharp grooves in it now the crankshaft itself really only suffered damage on the one connecting rod now that connecting rod must have been knocking so badly that it actually chewed into the block into this part here now besides this piston ring some subarus suffer from broken ring lands now the ringland is this area here where the notch is for the piston ring to sit inside and sometimes there's a crack across there and a chunk of it might actually come loose causing you to lose compression and that's just mainly due to the material used on the piston head now in terms of how this engine gets its oil it's going to start here at the oil pickup tube inlet it's then going to be drawn over to this section here which corresponds to this section here on the oil pump the oil pump is then going to pressurize that oil and send it back out this port over here which corresponds to this port on this half of the engine the oil is then going to make its way through the oil filter and then back out through here and then through another oil galley that runs crossway this way and then through another oil galley that runs down to all of these main bearings and some of that oil is then going to be sent over through this hole which is going to correspond to this hole on the other half of the block and that's got more galleys over here that's going to lubricate these two main bearings here surprisingly this bearing is not lubricated there's no hole for it and this one here gets its feed from the one that goes to the head you could see on this one here this is the galley that's going to take oil up through this little hole over here and if we come across the block that hole corresponds to this hole over here which is going to take oil into the head to lubricate all the rocker arms and camshaft and with the block split you can see this is the passageway that crosses over coolant from the water pump side of the engine to the other half of the engine now one other thing that i've noticed on this engine is just how far forward it sits relative to the center line of the front wheel it's just like a front wheel drive car almost where you have a huge front overhang most of the engine here is in front of it and that's because of the all-wheel drive setup this engine situated longitudinally and you can see here this is where the transmission sits and the drive axle that goes out to that front wheel now in comparison here's my lexus gs 350 which has a longitudinally mounted v6 engine you can see that the front of the engine here almost lines up with the center line of the so everything is kind of pushed back in this engine bay giving it a fairly short overhang in the front and because the transmission is underneath the vehicle on all-wheel drive models there's a prop shaft that runs to the front and then underneath the engine to the front wheel now if we compare that boxer style engine format to say an inline engine this one being a volvo five-cylinder you can see that its footprint is much slimmer than that boxer engine but this engine sits upright which is going to give you some design restrictions with your vehicle meaning that your hood line has to be a little bit higher to clear it and it's also going to raise the center of gravity funny thing is this super actually has an inline six sitting upright underneath the hood although it's a very low hood line link in the description above if you want to see more under the hood now i have a full teardown and analysis of this volvo engine but generally speaking you could see that the inline engine has the pistons moving up and down which means that the secondary forces and thus accelerations are going to vibrate the engine up and down now here we've got a v6 engine so three cylinders on this side and three cylinders on that bank and you can see that these cams lead up to the crank here at the bottom forming the v-shape now the v engine isn't going to be nearly as tall as an inline engine but it's also going to be more balanced than say an inline four or even a boxer engine because the secondary forces cancel each other out making it much smoother and that's pretty much what's inside of a subaru boxer engine and what makes it so unique from a regular four-cylinder now if you've got one of these engines make sure you keep up on maintenance because as you can see this could get pretty expensive now make sure you follow me on instagram for more behind the scenes footage and subscribe to see more videos just like this one and check out my new subaru engine coffee table just like the engine itself this table sits nice and low flat and wide and i've even turned the flywheel into a working clock