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How to Change the Spark Plugs in your 2004-2008 Toyota Sienna

It's Gotta Be Done

Toyota recommends the replacement of spark plugs, typically when your vehicle reaches 120,000 miles. This routine maintenance can be very costly. The dealer I talked with proposed $900 for the job, which seemed unreasonable for a set of cheap spark plugs. Let's look through the work that is required, and you can make the decision yourself whether to do it yourself.

Since I have done this already myself, this article should serve as a helpful guide for those of you in the same predicament. There really isn't any need to disassemble a large part of what's under the hood. I try to show how to get the spark plugs replaced with the least amount of work required. I estimate it will take two to four hours, but you need a long reach and strong nimble fingers.

What Do I Need?

  • 4- and 8-millimeter Allen wrenches
  • 10-, 12- and 14-millimeter sockets (the 10-mm will be used most often)
  • Rubber spark plug socket (5/8 inches)
  • 10-millimeter wrench
  • 12- and 14-millimeter ratchet wrenches (makes things easier...)
  • Small ratchet with extensions
  • Flexible ratchet
  • Gloves
  • Standard and needle-nose pliers

Optional

  • Paper towels
  • Flat head screwdriver
  • Duster
  • Electric tape
  • Hat (your hair will be brushing against the vehicle a lot)
  • Towel (to cover the parts that you will be lying on)

First Disconnect the Battery

While wearing gloves, use the 10-millimeter wrench to loosen the bolts on the battery. Carefully remove both sides and separate them from the battery, being extra careful not to touch both connections at the same time (otherwise you could get shocked). There should be a slight sizzling sound, which is okay.

Place a towel over the battery area, or otherwise make sure the area is safe for working. There will be lots of time spent leaning over this area, so make sure it's set up in a way that is safe.

First Set of Three Spark Plugs

The spark plugs are split into two sections, three in the front and three in the back. The front three plugs can be replaced in about 15 minutes, but be prepared to set aside an additional two to four hours for the rear three plugs.

Remove the Cover

Grab the smaller Allen wrench and unlock the three bolts on the front of the frame. Once you unlock them, it should be fairly quick. If you have trouble getting a bolt to unlock, use pliers on the Allen wrench.

Change the Spark Plug

First remove the bolt on the side, unclip the wiring, then gently pull the long tube out of the hole.

The Special Spark Plug Tool

There is a 5/8th-inch socket specifically designed for spark plugs. This socket has a rubber lining which allows gripping and gentle installation. Connect this to a ratchet with a long extension, along with the socket ,and unscrew the spark plug from the hole. Once it is pulled out, place the new spark plug in the socket and gently screw the new one into its place.

Replace the Other Two Front Spark Plugs

Repeat these steps to replace the remaining two front spark plugs. On the three rear plugs, the method will be the same, but with less room. On the rear plugs no detaching of the wire assembly should be necessary (as they made the cables long enough to pull the spark plug tube out without detaching the wiring).

Remove the First of Three Items

To get to the rear spark plugs you will have to detach three items. The first and simplest is the set of cables above the exhaust manifold, just above the new spark plugs. It's in the way and will need to be moved. Only three 10-millimeter bolts, a cable, and a few pipes need to be detached and moved. Disassemble so that this piece can be moved over the front spark plugs, out of the way, but there is no need to take anything out of the hood yet.

Start Removing the Exhaust Manifold

Just to continue in this section, remove the four bolts that require a 8-millimeter Allen wrench. No need for any extravagant tools here. Once the bolt is unlocked, it can be removed by hand. After removing the four bolts, remove the two 12-millimeter bolts on each side, and then remove the metal framing. Take this piece of framing out of the hood and set it down for reassembly later. Unfortunately, this is only the beginning of getting that exhaust manifold off.

Remove Item 2 of 3: The Air Filter Unit

Proceed by removing just the tubes and bolts so you can pull out the air filter unit. It's fairly simple. There are two small 10-millimeter bolts and several tubes to disconnect. Pulling the large tube off the exhaust manifold on the right should take a little force, but you can easily reassemble it later. Place this piece outside the hood, next to the engine cover and exhaust manifold bracket taken out earlier. This is the last piece that will be pulled out completely.

Remove Item 3 of 3

The challenge with removing the exhaust manifold is that it is bolted on with three brackets in the back that you will need to get to. See the picture below. The first bracket is not at all flexible and has a 14-millimeter bolt. The other two are 12 millimeters, and can be removed using special tools. The short 12- and 14-millimeter ratchet wrenches are perfect for squeezing in and getting those out where there is little room to move. A great deal of force is needed, so it might make sense to put on long sleeves before reaching into the back.

Remove the Manifold

Proceed in removing the manifold. There are two pipes connected to the aluminum part on the right which will spit out a little antifreeze. Not much will come out, but be aware when removing those pipes. Attempt to pull out the big piece as one and disconnect any lines that are connected. It may help to use colored tape to identify which pipe goes to which, but mine were fortunately color coded already. You may need to use needle-nose pliers to gently remove the older pipes that are sealed.

Change the Spark Plugs! (Finally)

The method is the same, but this time the cables are longer (as previously mentioned) and the wiring doesn't have to be disconnected. Unbolt the spark plug tubes and proceed to replace the spark plugs. The flexible ratchet will be very helpful in this case. I found that separating the ratchet from the extension helped me fit it in; then I would re-attach it when unscrewing the spark plug.

Reassemble

Now that the spark plugs are replaced, reassemble everything. Getting those three bolts back on may very well be as difficult as taking them off, and took me about the same amount of time. Once they are back on, the rest should go fairly quickly.

IMPORTANT: Make sure that every pipe and wire connection is double-checked, and that every line is connected thoroughly and routed to the correct place. These connections are critically important and could mean serious damage to the vehicle if not correctly assembled.

Clean it

There is an option to clean the pieces as you reassemble. Might as well, as these pieces are vacant and easy to access.

Check Your Work

As with any service maintenance, start up the car and let it sit idle for a bit. Some would suggest taking it for a short drive to make sure the "check engine" light doesn't come on (which would suggest a pipe or wire assembly was not put back in the right place). After a bit of testing, the car should be ready for use.

I did notice that the front spark plugs appeared to be under more stress than the rears (as shown), which may explain why some suggest changing the fronts periodically. This would certainly be easier than changing all the plugs.

Hope this helps in your project. I wish you the best!

Comments 2 comments

Jill 5 months ago

I did this spark plug change myself today at my mechanics garage because they were too busy and it needed to be done. It took me 4.5 hours and I didn't remove anything but the engine cover(plastic with the Toyota symbol on it) and I had to unclip the middle cool clip to get it out to maneuver the removal and replacement of the spark plug. I was on all kinda of forums looking up how it was to be done, but in the end didn't have to remove anything. I am a woman and have slender arms and hands: just wanted to say, it an be done and it only cost me the price of the spark plugs- 50$ I have a Toyota sienna LE 2003. I have a ton of respect for me Janice and what they do because this is the first time I've ever done any fix myself. Feeling pretty good and pretty tired!


Clinton 8 weeks ago

You really should check the gap on the plugs before installing them. Not doing that simple task could make the engine run rough (or not at all).

To do this, get the gap setting for the engine from the auto parts store and buy the $1 gap tool.

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