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How to Replace Spark Plugs 13-18 Subaru Forester

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Hi my name is Mike from 1AAuto. We've been selling auto parts for over 30 years!

We're going to open the hood. The hood release is right under the dashboard here. Pull it down and the front of the safety latch--push it to the passenger side. Hood has struts on it, it will lift right up and remove the native terminal. Use a 10 mm wrench, loosen it up, if it gets loose you can just wiggle it off and it should pop off of this bracket here. Put that aside, and remove the protective cover on the positive terminal. It slides right off the top.

Loosen the nut here, and this is the live post. It's the positive post to the battery, so when we are using this wrench, just be sure you don't touch it to anything metal because it will short out, to ground, but we are going to loosen it. And then once it's loose you can just wiggle the terminal off.

Use a 10 mm deep socket, we're going to loosen the two bracket nuts. Start with this one. You don't need to loosen these all the way off, you just need to get them loose enough so that they can unhook. So that one's loose, we can get this one loose and it will be easier to see in the front of this. It's got a little hook at the bottom of it, so once it gets loose enough, you can unhook it. It's a lot easier if you don't take the nut all the way off when you go to reinstall it, so once it's loose you can just push it to the side and unhook it and do the same for this one. You might have to wiggle it around a little bit. So I'll just wiggle it out here and then we pull the whole damn bracket up and out.

Now I can grab on to the battery, and lift it out of the car, try to get my hand underneath it. Pull this little plastic battery tray out of the way. Two coil packs with the spark plugs are located here and here. We'll have to remove those to replace the spark plugs. We are going to use some water displacement oil on the connectors to help remove them. Connectors can get built up with dirt, and a little bit of oil helps them slide off easier. Use a small flat bladed screwdriver, push the locks. And push them out with my thumb as I unlock them. I am going to unclip both, back one can be a little bit trickier. Reach in from the top here, push the lock in and reach in with my fingers and push it off. They are the same connector but the wiring is shorter on the rear one, so you can't mix them up.

I am going to remove one coil pack at a time, and I am going to start with the rear one. There's a 10 mm bolt, a single bolt holding it in, so I am going to use a 10 mm socket ratchet and break that bolt free. So once I break it free, it should come out pretty easily. Get it started a little bit with the ratchet, and I can reach in here and grab it with my fingertips. Spark plugs aren't difficult on this car, they just take some patience. Pull the bolt out--it's not captured in the coil. Put it aside so I don't lose it. With the bolt removed, now I am going to reach down and pull the coil out inside of the engine. I might have to wiggle it back and forth and just get it free. Once it's out just kind of slide it out.

We're going to use some compressed air. We're just going to blow out the spark plug hole to make sure there's no debris in there, we don't want it to possibly fall in the engine. Going to use a 9/16 spark plug socket. It has a special rubber grommet in there to hold on to the spark plugs so it doesn't fall. And a short extension, just use whatever combination of extension that you need to get to it. It's a little tricky to get in here. Get in to the opening. I am going to take the socket and get it in here. Get it started. I will take my extension. Get it in here. Try to find it and make sure it's on the spark plug. Take my ratchet, it shouldn't take too much effort to break these free.

I am going to take the ratchet out of here. Get the extension in there. Just going to spin it out. I was using my fingers on the end of the extension--now it's loose enough. Take the ratchet off of there so it doesn't get stuck up against the frame rail. Take the extension. It's too long to get it off the frame rail, so I had to pull it out. So I threaded the spark plug in just a tiny amount to give me enough grip to pull the longer extension out. And then I am going to work it out with this short one. Pull that extension off, and pull the socket out with the spark plug.

I am going to put the new spark plug in. It's already gaped from the factory. And I've got it in the spark plug socket, so I am just going to carefully put it in the hole for it, in the cylinder head. And get it set up, and I will put the short extension I had to give myself a little bit of extra give to it. Now you want to be careful pushing the extension in because you don't want to push the electrode of the spark plug down. And then just sort of find the threads with your fingers, get it started, make sure it threads in nicely. So this one's going in. Before it gets too far, I am going to pull this little short extension out. I am going to put the longer one on, so I do these one at a time. Alright and just thread it all the way down my hand.

Again, just take your time with these--they are pretty difficult. It can be frustrating so just take your time with them. But they are not impossible. To work on these is 13 [inaudible 00:09:09] pounds. If you can manage to get your torque wrench in here, you can use it. Our torque wrench won't fit, the clearances are just too tight. I'm going to tighten it up by hand, and when I feel there's a washer in the spark plug that crushes. And you can feel it crush, and it really doesn't take much effort. You don't want to over tighten them but just do your best. It's very difficult to get anything in here. Right when you about feel it bottom out, that gasket should be crushed and just go a tiny bit more and you should be good. Now I got to get these extensions and sockets out of here. We'll put the coil pack back in, the boot on it is pretty floppy. Going to get it in place, make sure it's over the spark plug. Push in with some resistance. Get the retaining bolts caught. Start it by hand, thread it in. I'll tighten up this bolt, I have to really get it in there finger tight first. It's just a seal bolt going in to the aluminum valve cover, so you don't want to over tighten it. Once you feel it get tight, just go a little bit more. And then you're good. And we'll go and plug the coil back in.

It won't really click, but it's locked in to place. Now I'll move on to the front one, and use the 10 mm socket ratchet. Break free of the little 10 mm bolt, that holds the coil pack on. Get the right angle here to turn it. To get it free, spin it out with my fingers. With that loose, I can wiggle the coil out. Slide that right out. Again use my 9/16 spark plug socket. Get it in here. Put the socket in first. Slide the extension in. Struts down over the spark plug. Break it free with the ratchet. Start to loosen it up. It's loose. I'll take it out with my fingers, the extension is too long so I am just going to thread it in just a little bit more. Pull the extension out, put the short extension in, and grab it. You're just going to have to use a combination of extensions.

Pull it out. So I've got the plug in the socket with the short extension in to the opening spark plug. Thread it in by hand and get it started. Before it gets too far in there I am going to pull this extension out. Use the longer extension, try to thread it down as far as I can go with my fingers so there's less for the wrench to turn. And less for the torque wrench to turn, see if I can get the torque wrench in the front here. So we're going to do that. I can't get a torque wrench in here, so I'm going to use a ratchet, and then just carefully tighten it down by feel. I want to feel that gasket crush, so once it gets tight, I'll just go a little bit more. So now I can feel it getting tight.

It's just getting tight now. I'll just go a tiny bit more once it bottoms out, like 1/8th of a turn. Now put the coil back in, it should find itself over the spark plug. It'll line up, roughly where the hole is for the retaining bolts. The retaining bolt started by hand. It's just a steel bolt, [inaudible 00:16:04] aluminum so I'm going to get it started by hand first. Thread it, just tighten it up again. Don't forget it's a steel bolt going in to an aluminum head. So once you feel it get tight, just stop. You don't want to break it off. Don't forget to reconnect the coil, the wire fell down here. It only reaches this coil. Now we'll get it plugged in.

To remove the intake duct, take a flat screwdriver, turn the clips pop them out. Do the same for this one. Now you lift this up and out of the air box and we'll put it aside. Use a 10 mm ratcheting wrench and remove this nut right here. It's holding the air box in. Take that nut off with my fingers, push off the bracket. I'm going to use a long extension and my 10 mm socket and ratchet. You can use a shorter one, whatever one you have access to, to get to this bolt down here. Just going to loosen it up and I'll pull it out. Pop the clips off, top of the air box, open it up. Unhook it.

And kind of maneuver it out. Pull it right out of the vehicle. I'm going to unplug the mass airflow meter, so unlock it. Sometimes you push it in first, unlock it, pull it off. This hose clamp is unfortunately positioned upside down, which is kind of annoying, but I am going to loosen it and pull this whole cover off with a mass air flow meter in it. Going to use an 8 mm socket and ratchet to loosen this hose clamp. Get it loose enough. Don't want to take it all the way off. Sometimes you have to hold the socket with one hand so you can get enough friction on it for the ratchet to work. Once it breaks free, so I'll actually spin it around, so when I go to reinstall it, it'll be up top so it's easier to get to. But this should pull out of the hose now. Using a flat blade screwdriver to help me pry this off. Just have to break the seal. There it is.

So I can have access to this bolt right here and this bracket. I'm just going to use some needle nose pliers and push this clip. Squeeze it together. And I can push it out of the bracket. Just like that, and that will give me access to that bolt now. I am also going to need to move this clip off of here with the harness, because I need to move this bracket out of the way. Get those clips pushed in, and push it through. That's all it's going to take. Going to use a little rust penetrant on here, and I'll remove it with a 10 mm deep socket.

And I'll spin it off with my fingers. Alright, so that will come off of there. Spray some rust penetrant in here. Will use a 12 mm socket extension swivel. Break it free. There we go, with the air box removed and this bracket removed, from this point forward procedure is the same as the other side. You are just going to have to work your way through it and take your time. So I'll spray some water displacement oil on these connectors before I pop them off.

I am using a 10 mm socket ratchet and remove the retaining bolt holding the coil to the engine. Now we are going to reinstall our bracket. So it does have a top stud here, and gonna get the bottom bolts in to the hole, caught. I'll just keep it kind of loose so I can move it around, put that in to there. I'll tighten the bolt up, reinstall this little nut. Once it gets tight, stop. Now push these electrical connectors back in where it was. Clip that in and put this harness back in. So I'll put this part of the air box back in.

So it goes in to the opening, there is a tab that's going to line up with the hose right there. And I rotated the hose clamp in a way that I can get to it from the top. Use the 8 mm and the extension and I'll tighten it up. When I feel it get tight, I'll stop. Plug the mass air flow meter back in. I'll reinstall the air box, kind of maneuver it down in to place. So those are going to have to lock in to the bottom. So it's going to sit like that, and clip it together. We'll line it up with that stud in place. Put this bolt down in here. Get my extension and 10 mm. Find the hole for it and tighten it up. When it gets tight, stop. I'm going to reinstall the nut on this stud here, and use the deep socket, as soon as I feel it get tight, stop. Going to reinstall the air duct, feed that in, in to the air box. It should slide right in to place.

That lines up the hose on the radiator support, put the push clips back in. Push them in, reinstall the plastic battery tray. Let's get these two holes are going to line up with the two holes in the frame, and the arrow points to the front. It just sits like that. We're going to reinstall the battery. Let's get this little foam cover on it, from the factory. Let's get it on that battery tray there. I'll reinstall the battery tie down, the one with the ... the shorter one with the hook goes towards the back. It's going to be hard to see, it has to go down and hook in like that. And then the front one will go in and hook in right there. These are deep socket, tighten them up. Make sure it's still hooking in, actually if it helps, you can pull it up so it's tight. And then thread this nut down to give it some tension. Do the same for this one.

This one is a lot closer, okay and now I'll finish up and tighten those down. I can go evenly, you don't want to over tighten them, you can crack the battery, but you don't want it to be loose either, because you don't want the battery moving around. It'll be tight, once you feel them get tight, you can basically stop. Reinstall the positive battery terminal. And you want to have the keys nearby just in case the alarm goes off. Sometimes that happens when you reconnect a battery. But we don't have the negative terminal attached yet. So until we attach the negative terminal, and again I will take my 10 mm wrench, and I'll tighten this up. And since this is the live terminal of the battery, I'll be careful not to touch any metal while I am tightening this. I don't want it to cause a short.

Let's get it tight, a little bit tighter. Once you feel it tight, you can stop. And just make sure it doesn't come loose, reinstall the positive terminal cover protector. And now is the moment of truth, when we'll see if the alarm goes off. So I'm going to put this little holder down, back on to here. The negative terminal just pushes down. I'll reconnect this, no I don't think the alarm's going to go off on this car, so we're lucky. I'll just tighten this down with a 10 mm wrench. Make sure it's nice and tight.

Thanks for watching. Visit us at 1aauto.com for quality auto parts, fast and free shipping and the best customer service in the industry.

Tools needed for replacement:

    General Tools

  • Telescope magnet
  • Flashlight

  • Materials, Fluids, and Supplies

  • Rust Penetrant

  • Ratchets & Related

  • Torque Wrench

  • Screwdrivers & Related

  • Flat Blade Screwdriver

  • Sockets - Metric

  • Complete Metric Socket Set

  • Sockets - SAE

  • 5/16 Inch Spark Plug Socket

  • Wrenches - Metric

  • Complete Metric Wrench Set


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