2002 Subaru Impreza Brake Pad Replacement

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Tools Required

  • 14mm socket
  • 19mm socket
  • 1/2" Torque Wrench
  • Flat-blade screw driver
  • Jack stand(s)
  • Jack (preferably a floor jack)
  • Bungee cord or string (for holding the caliper out of the way)

Optional Tools

Materials

  • Brake pads (duh!)
  • Silicon brake grease (i.e. Subaru 26298AC00 (Molykote AS880N), or Volvo 1161325-4 PTFE Silicon Grease )
  • Non-Chlorinated Brake Cleaner (optional)
  • Loctite (optional Loctite 242 (Blue)
  • Shop towels or rags
  • Mechanic's latex gloves (just cause you work on your car doesn't mean you have to look like a grease monkey for the next few days)

 

 

Instructions  (click any picture for a full resolution image)

Start by jacking the wheel that you are going to work on up and off the ground. But before you get too far, only raise the wheel until just before it loses contact with the ground. Now is the time to loosen the wheel lug nuts. You just need to break the lug nuts free, so you can almost turn them by hand (without the wrench). Do not remove them just yet, finishing jacking the wheel all the way off the ground. Lugs nuts should always be removed opposite one another. You should never remove them 'round-the-clock', as this can lead to breaking a stud. The picture shows the correct order to loosen, and tighten lug nuts. Click on the picture for a full size version
Image to be provided later... Place a jack stand at suitable location as a safety measure in case you jack fails. Lower the jack so that the jack stand is now supporting the weight of the car. You can finish removing the lug nuts, and remove the wheel.
lower-guide-pin lo With the caliper now in plain view, you need to locate the bottom caliper bolt. Subaru refers to this as the lower guide pin. Using the 14mm socket/wrench, remove this bolt. You do not need to remove any other bolts) to access the brake pads.
You can now rotate the floating part of the caliper upwards and off of the rotor (the pads should remain in place since they are secured with a number of retaining and anti-rattle clips). Click on the picture for a full size version
Click on the picture for a full size version Secure the caliper out of the way. I prefer a bungee cord that is attached to the spring, as soon in the picture.
Now that the caliper is out of the way, you can remove the inner and out brake pads. A flat blade screw driver will help you slowly pry the pads out. You should slide the pads off the rotor towards the outside edge of the rotor, or from the center out. This is the easiest way direction that will avoid damaging your retaining clips. Click on the picture for a full size version
Click on the picture for a full size version With the pads out, inspect them carefully. You will notice that a stainless steel shim is attached to the back side of each pad. Actually there are two of these shims. You need to remove them (without braking or bending them).
Now clean the shims (non-chlorinated brake cleaner is excellent for this). They don't have to be spotless, but should not have any large deposits on them that would interfere with them laying and stacking flat. Click on the picture for a full size version
Click on the picture for a full size version Next if there is a buildup of brake dust or dirt on the piston boots (the rubber bellows that connects the piston cups to the caliper body) or guide pin bellows, then you should gently remove the brake dust. A small brush, or shop towel will do. I prefer not to use any chemicals since they can do long term damage to these boots. This step, while not necessary, is a good preventative maintenance idea since objects caught on the dust boots can eventually cut into them and cause them to tear.

You should also check the condition of these dust boots/shields. If they are torn or cracked, then they should be replaced. If the pistons boots need to be replaced, then it is probably a good time to stop and put everything back together and let a professional shop replace/rebuild the calipers. If the guide pin boots are torn, then these can easily be replaced.
Next you need to clean the contact surface of the piston. For this I use a paper towel sprayed with brake cleaner, making sure to minimize contact with the rubber bellows we just cleaned. The piston surface should be free from all deposits. If it is not your brakes will probably squeal when applied. Click on the picture for a full size version
Click on the picture for a full size version Now you need to depress the piston(s) back into the caliper housing, but FIRST, pop the hood, and remove the filler cap from the brake master cylinder. Make sure to place a towel around the opening to catch any overflow. We are doing this because we are going to be forcing the fluid out of the brake calipers and back into the master cylinder. As we do so this brake fluid will typically overflow out of the reservoir, and can remove your paint as well as a number of the better paint removers out there.

NOTE:

As your pads wear down the fluid level in the master cylinder drops. You are not losing fluid, perhaps like the coolant from the radiator, but instead the fluid is being displaced into the calipers. This is sort of the same principal as an hour glass. When you reset the caliper pistons, you are displacing the fluid back up to the master cylinder. If you have been adding brake fluid while the pads were wearing down, you will now have too much fluid in the system, and this is what can cause the excess to overflow out of the master cylinder).
Now you are ready to compress the pistons back into the calipers. If you have a piston compression tool, then it will make the job easier. For the front dual piston caliper, I always use one of the old pads to spread the load out. You are trying not to push the pistons back into their housing lob-sided. If you are not carefully and just force the piston back in by only applying pressure to one side you could score the cylinder, or piston, and then have a leaking caliper. Depending on which part is damaged you will have to at a minimum rebuild the caliper, or worse replace it (not bad if you are planning on a big brake kit, but otherwise just make sure you slowly and carefully press the piston all the way back into the caliper.

If you do not have a pad compression tool for the front calipers, then make sure to use one of the old pads to distribute the load while you are using a pry bar, or whatever you have to press the pistons back into the caliper. It is important to press both pistons back together at the same time, otherwise it will be like playing one of those Bop the Weasels games, as you push one piston back in, the other will slide out, and you can go back and forth between pistons forever.

Click on the picture for a full size version
Click on the picture for a full size version With your new pads, it is time to make the shim sandwich. On a dust free surface, apply a thin layer of silicon brake grease to all sides of the shims. The dark, slotted shim goes first. Just make sure that while re-assembling the shims that the grease does not find its way onto the front side (or business end) of the pads. Both the shims have tabs that should line up with pad, and secure them to it, via friction.
Now install the pad and shim assembly back into the caliper and slide then in until they are against the rotor. Install them in the opposite direction that you took them out (from the outside edge of the rotor, and towards the center of the rotor). You may have to fool with the pads a little and wiggle them into position, past the anti-rattle clips that will hold them in place when they are in position. Click on the picture for a full size version
Click on the picture for a full size version You can now slowly lower the caliper body that was up and out of the way. Note that as with all floating calipers the caliper body is allowed to slide inboard and outboard on the guide pins. Since you are replacing worn pads, the caliper should be slide in and out to line up over the pads. If you cannot lower the caliper over the pads, it is typically because the pistons are still protruding too far out of the caliper body, and are catching on the edge of the pads. You should never have to force the caliper back into position! If this is the case, then just make sure the pistons are compressed all the way into the caliper body and try again. Also make sure the pads are touching the rotor. The caliper should eventually slide right back into position.

Now just re-install the lower caliper bolt. This bolt should be tighten to 37N-m of torque using a torque wrench. Since it would be a really bad thing if this bolt were to come loose, I always us a drop or two of Loctite.

Caliper Bolt - 37 Nm, 27 Ft-lbs

Click on the picture for a full size version
Click on the picture for a full size version

Reattach the wheel and tighten the lugs nuts as tight as possible (but no more than 65N-m). The rear wheels can actually be fully tighten with the wheel off the ground due to the differential, but the front wheels will rotate while tighten the lug nuts.
Lug Nuts - 65 Nm, 48 Ft-Lbs

An old Volvo recommendation is to apply a light application of the wheel bearing grease to the wheel studs. This is especially effective in wet climates and prevents the studs and lug nuts from rusting. Once lubricated the torque settings are now called “wet” and will be lower than the shop manual “dry” values. Typically an 80N-m dry setting equates to 65N-m wet. Even though I live in Southern California, I always lightly grease the wheel studs to keep the rust off

Now lower the wheel again to the point where it just starts to touch the ground. You should now be able to finish tightening the lug nuts to 65N-m, again using the opposite tightening pattern. If the full weight of the car is on the wheel before the lug nuts are fully tighten you run the risk of either stripping a lug nut, or mounting the wheel off-center, which can lead to it falling off later on the freeway, or a bumpy ride.
That's it. Now just repeat for the remaining three brakes. While it may sound like a lot, it is actually quite easy, and should only take about an hour to do all four wheels.
The real concern and why these instructions are so long is that you are going to be working on the main component of your car that allows you to STOP. Any failure in this area is going to result in an accident, guaranteed! Brakes should not be fooled around with. They should be treated with the respect that you place on your own life.

 

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