811615, 822615 - Air Oil Separator WRX 2002 - 2014, STI 04-20
811615, 822615 - Air Oil Separator
Subaru WRX STI 2004 - 2021
Subaru WRX 2002 - 2014
Subaru Legacy GT, Outback XT 2005 - 2009
Subaru Forester XT 2004 - 2008
Congratulations on your purchase of the COBB Tuning Air Oil Separator! The following instructions will assist you through the installation process. Please read them BEFORE beginning the install to familiarize yourself with the steps and tools needed. If you feel you cannot properly perform this installation, we HIGHLY recommend you take the vehicle to a qualified and experienced automotive technician.
Table of Contents
A Special Note on Hose Installation
When installing the hoses and lines to and from the COBB Air Oil Separator, take special care to route them away from any sources of heat, ensure that they are free of kinks or obstructions, and secure them properly with zip ties to prevent movement and chafing. Utilize spring clamps at every connection point to avoid the potential for an air leak. Additionally keep in mind that the engine will move slightly so leave a small amount of play in the lines where it goes up to the AOS to allow for some movement without causing damage or stress on the lines.
Quick Reference for Hose Attachment
Stock TMIC Removal
- WRX 2002 - 2007
- WRX STI 2004 - 2020
- Forester XT 2004 - 2008
- Locate your stock bypass valve.
- Using a pair of pliers, remove the return line from the bypass valve.
- Remove the vacuum line from the factory bypass valve.
Using a 12mm socket with ratchet, remove the 2 bolts that hold the bypass valve in place and remove it from the car.
TIP: Make sure to keep an eye on the factory gasket behind the BPV. It can fall when you remove the valve and end up in difficult to reach locations!- Remove the bypass valve.
- Remove breather tubes from intercooler. Dikes can be helpful when removing the metal clamps or zip ties.
- Loosen the turbo outlet clamp using a screwdriver or appropriately sized socket (Typically 7-8mm) along with the (2) throttle body clamps using a screwdriver or 8mm socket.
- Gently wiggle TMIC free from engine bay by sliding it back and then out. Be careful to not damage your windshield wiper cowl.
With it off of the car, you can remove the metal PCV lines permanently.
This removal applies to the following vehicles
- 2008 - 2014 WRX
- 2005 - 2009 Legacy GT
- 2005 - 2009 Outback XT
- 2008 - 2013 Forester XT
- Locate the factory BPV and remove the recirculation hose by squeezing down the hose clamp with your pliers.
- Remove the vacuum reference line from the rear port of the BPV
- Moving to the other side, unbolt the flange where it meets the turbo using a 12mm socket.
- Undo the hose clamp attaching the throttle body coupler to the intercooler. This will typically require a phillips screwdriver, 7 or 8mm socket.
- Unbolt the remaining 12mm bolt going to the intercooler support bracket and remove the intercooler from the car.
Mounting Prep
Cruise Control (02-05 GD Chassis)
Cable Control Throttle Body With Cruise Control and Horn.
- If present the cruise control will need to be modified for the bracket to fit properly. To do so start by removing the bolts holding the silver bracket to the strut tower with your 10mm socket.
- Then remove the bolts from the black bracket holding that to the vehicle as well.
- Next you'll want to unbolt the bracket from the cruise control module using a screwdriver.
- Trim the black bracket using a saw or cutting disc. Make sure to wear appropriate protective equipment.
- Reinstall the cruise control module using the factory hardware.
- Bolt the modified bracket into the lower bolt hole the silver bracket utilised.
Horn Relocation (02-05 GD Chassis)
Some vehicles mount a horn to a bracket on the top of the strut tower. You'll want to move this out of the way as it blocks access and space for the AOS.
- Using a 12mm socket unbolt where the two horn brackets meet.
- Remove the two 12mm bolts holding the horn bracket to the top of the strut tower, the bracket can now be removed from the car and will not be reused.
- Move the horn towards the front side of the strut tower and bolt it down. It will give you more slack if you undo the limiting tape on the horn harness.
DRL Resistor Relocation (GD Chassis 02-07)
- Some models have the DRL resistor mounted in various ways in this area. You'll want to make sure it's cool before doing anything as it can get incredibly hot. Undo the two 12mm bolts holding the resistor to the bracket.
- Relocate this unit to the bottom of the forward two holes on the strut tower. You may need to flip the unit over or remove it from the 90 degree bracket to make it fit with the brake lines.
Harness Relocation (07 GD 08+ GR Chassis)
- Using a screwdriver, gently lift downward on the retaining pin holding the main engine wiring harness to the bracket. While doing so wiggle the connector towards the space the TMIC used to occupy. It should slip off easily if the pin is out of the way.
- Squeeze the harness clip holding the wiring harness to the bracket. Remove the bracket from the car and set it aside as it won't be used again.
- Disconnect the o2 sensor connector from the harness, and squeeze the clip to remove it from the bracket.
- At the top of the harness near where the corrugated plastic sheething stops there should be an extra piece of electrical tape on the top few inches limiting the reach of the o2 sensor harness. Remove this strip but leave the rest of the tape in place for protection. You should be able to see an end to start unwinding from.
- Clean the adhesive off of your hands and the harness with either soap and water or a small amount of brake cleaner sprayed on a cloth.
- Release the harness clip holding it to the top mount intercooler bracket. This should allow you a bit more freedom to move it around.
Mounting Area Modification
- Using a rag covering a screwdriver or pry bar, gently GENTLY move the brake lines up slightly. Getting the top one to an even height with the nut on the strut tower and the lower one spaced similarly to stock should give you the space required.
- Near the turbo you should see a 90 degree line coming up from the engine block and going into a white fitting, then the turbo inlet. (note the electrical tape to keep it from leaking which doesn't actually work for longer than about 10 seconds)
- The wiring connector does double-duty also holding the white sensor in place. Pressing down on the release tab pull outward gently to pop it out.
- Following that hose down, you should see a another line teeing off to a metal fitting and a smaller hose. Undo the hose clamp holding the smaller hose onto the pcv valve.
- With that line undone gently pull upward on the hose with the white connector, it should pop off of the crankcase breather / oil drain hose. Don't be afraid if it come off in individual pieces. The crimped metal clamps can be opened by inserting a small flat-blade screwdriver and gently turning it to bend the clamp open.
- Take the provided 5/8" drain line and install it onto the larger side of the plastic y-fitting that was provided. Secure it with one of the provided clip clamps by simply pushing the clamp together with a pair of pliers. until it buts up against the raised portion on the bottom piece. DO NOT GO OVER THE HUMP
- Using the same method and clamp style, attach the oil drain back to the drain line on the block. If the fitting appears slightly loose you can squeeze the looped portion of the clamp lightly with some pliers to tighten it up.
If you need to remove the clamps for any reason you can use a small screwdriver in this area pushing lightly down and outward to pop the clamp free.
This assembly essentially replaces the drain and tee from this assembly
AOS Pre-Assembly
- Install the coolant lines. Using a 10mm allen key Gently snug it in place (being careful not to crush the o-ring).
- Install the provided bracket onto the AOS. Typical mounting is one hole below the top for GR vehicles 08+ or all the way at the bottom for GD vehicles (02-07), however on this car and some others, the firewall bends out and hits the top. We recommend test fitting it a few times by lining it up with the bolt holes from the harness bracket. Adjust your height and test fit as needed to ensure nothing is causing issues either on the top or the bottom. Tighten the three Allen bolts using a 5mm allen wrench or socket. Keep in mind the bend should face dowward.
GD
GR - Carefully navigate the AOS into place. you'll likely need to wiggle some things around like the harness and hoses to get them it in place. Bolt it down with the original or provided 10mm bolts. Loop the attached hoses out of the way for now. Tuck the lower coolant hose under the power steering bracket similar to the picture.
- Remove the bolt holding the power steering lines together using a 10mm socket.
- Take the provided flat harness bracket and install it into the engine side of the harness connector. It can help if you lift the tab again, similarly to how it was removed from the original bracket.
- Bolt it down loosely using the original power steering bracket bolt, then connect it to the other half to find a good point where the harnesses aren't being strained before tightening it down.
- Lastly we need somewhere for all the oil to drain back into the engine. Install the provided 1/2" line (with heatshield) onto the bottom port of the AOS using the pre-installed spring clamps on both ends. If you slide back the cover, the line should say 1/2" on it.