800660 - VA WRX, STI Coolant Overflow Tank

800660 – Subaru VA Coolant Overflow Tank

WRX 2015-2021
WRX STi 2015-2021

Congratulations on your purchase of the COBB Tuning VA WRX Coolant Overflow! 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

Parts List

  • Coolant Overflow
  • Coolant Overflow Cap
  • Coolant overflow upper bracket
  • Washer fluid tank adapter
  • Washer fluid fill hose
  • Washer fluid fill cap
  • Trim stud
  • m6x10mm flanged hex bolt
  • m6x16mm flanged hex bolt
  • (2) m6x10mm hex drive flat head screw
  • Flanged Hex Nut
  • 6mm flat washer
  • 6mm lock washer
  • 7/8 - 5/8 id Rubber Grommet
  • (2) 6mm silicone vacuum hose
  • m6 stud with 10mm hex

Tools Needed



Hand Tools



  1. Park your car in a flat level area and allow it to cool down.

  2. Squeeze the radiator hoses to make sure the coolant system is fully depressurized.

  3. As long as things are cooled down and the radiator hoses easily squeeze and don't feel as though there's pressure, remove the coolant cap.

  4. pull the hose gently out of the coolant overflow tank, most of the fluid should drain back into the tank.  If not lift the end of the hose upward to get it to drain back into the radiator.



  5. On the side of the overflow tank that is towards the headlight (not the radiator) you'll notice the end of the tank is underneath a small tab.  press this in to release the coolant tank and rotate it counter clockwise to free it from the fan shroud.  you can then lift up and remove it from the car.


  6. Set it somewhere safe, but leave it upright.  You'll use the coolant later on.

  7. Locate the windshield washer fluid cap.  Using a phillips screwdriver slightly turn the trim clip holding it in place, it should lift up slightly.

  8. With it slightly separated fit a trim tool or flat head screwdriver into the clip to pull the inside out slightly.  This should make it so you can now remove the lower half of the trim clip.

  9. Grab the fill tube and gently lift upward.  It should release from the lower half of the tank.


Washer Fluid Fill Tube.

  1. Remove the o-ring off of the stock fill tube and put it around the COBB Fill tube adapter.


  2. Gently push this into the washer fill port.

  3. Put the provided silicon tube onto the new fill port with the logo at the top.

  4. You can now put the small delrin fill cap into the tube.

Coolant Overflow Install

  1. Push the rubber grommet into the billet top bracket.


  2. Grab the shorter of the two provided bolts.  Push the bolt upwards through the hole the trim clip for the washer fill tube was originally in.


  3. Screw the billet trim stud onto the bolt and tighten the two hand-tight with a 10mm socket on the bolt, and a 17mm on the stud.

  4. STI FMIC Install Only

    Install the provided stud with a lock washer and flat washer on the short end into the threaded hole on the side of the overflow.


  5. Using the provided bolt, install the overflow tank to the unoccupied bolt hole on the frame rail behind the headlight.  Leave it loose for the time being.

  6. Push the rubber grommet in the top bracket over the installed stud with the tapered side of the holes facing up.

  7. Using an M4 Allen wrench, screw the tapered top bolts into the top bracket.

  8. STI FMIC Install Only

    The stud coming off of the side of the overflow tank should provide a point to attach to the brace on the side of the cold pipe, installing through the center aluminum spacer and tightening with the provided m6 serrated nut.



  9. Once you've gotten the top bolts tightened down you can go ahead and tighten the bottom bolt with an M10 socket and extension.

  10. Push the fill tube for the washer fluid into the pracket sticking out from the overflow tank to provide support.

  11. Install the provided length of hose over the factory radiator overflow nipple and run it down into the overflow tank making sure its just missing the bottom (you may need to trim 4"-5" off of the hose for it to fit perfectly).

  12. You can add the coolant from the old overflow tank into the new one at this time.  If you're doing a complete refill of the system you'll typically want to keep the overflow around 1/3 of the way full.

  13. Install the Delrin overflow cap.

  14. You're all done!  go out and enjoy!

Contact Us:

COBB Customer Support

Web Support and Tech Articles: COBB Tuning Customer Support Center

Email: support@cobbtuning.com

Phone support available 9am to 6pm Monday-Thursday. 9am to 4pm Friday (CST)


return to www.cobbtuning.com

Copyright 2024 © COBB Tuning Products LLC. All Rights Reserved. | www.cobbtuning.com