F30 BMW Passenger Seat removal/subwoofer replacement DIY guide

Foreward:

I thought I blew my subwoofer… Keyword there is thought.

On my way to an AutoX event back in November I was driving on the highway to the event, listening to news radio at a low volume. All of a sudden I get a “passenger restraint system” warning on the screen… It goes away pretty quickly and I think nothing of it. Keep listening at low volume, do the AutoX, start heading home, turn on some tunes to crank and boom… Crazy rattling from the passenger side subwoofer, exactly the sound a blown sub makes. Awesome… Turn the bass all the way down in the tone menu and live with it for a while.

Fast forward to last weekend, finally decide to take out the sub and start scouring eBay for a replacement. I take it out and notice this rivet in the subwoofer cavity beneath the seat.

Weird but for some reason it didn’t click that the loose rivet may have been causing the rattling. I check the woofers cone movement and notice no “voice coil scratching” at all when manually moving it up and down. I hook the woofer up in my garage to my “car audio garage system” and it’s working fine with no distortion at all. That’s when I realized the woofers movement is all below the grill we see from above the passengers seat and this is when it finally clicked that the AutoX must has moved that rivet under the woofer and caused the horrible blown sub sound.
Guess it was all just a coincidence. I thought for sure the warning I got shorted the sub out or something along those lines.

Technical skill
Cost
Time commitment
PITA factor

 

Prerequisites

  • T50 torx bit (I bought this one)
  • T15 torx driver/bit/whatever (I use this T-handle set)
  • Torque Wrench (I use my harbor freight cheapie)
  • 4 seat bolts: BMW Part # 07149321690 (Got these at the dealer for like $2 a piece)

Seat removal

  1.  First the warning from ISTA


    FWIW: I didn’t disconnect the battery or remove the head restraint. Also, I did not remove the seat out of the car, I just slid it back enough to get the subwoofer cover off and out.
  2. I started by moving the back of the seat all the way forward and moving the actual seat as rear-ward as possible. Remove the 2 highlighted bolts (on each rail)
  3. Move the seat all the way forward and remove the same 2 bolts
  4. If you are removing the seat completely
    •  Unplug the yellow harness underneath the seat
    • ISTA also mentions putting a protective cover on the door sill (risk of damage)
  5. If you don’t want to pull the seat out
    1. Lift the seat up a bit and slide it backwards, as far as it’ll go. Wedge something of your choice (my daughters turtle toy worked great) under the seat enough to give you some room to get your T15 torx driver in there.
  6.  Remove the 4 T15 bolts on the subwoofer cover
  7. Disconnect the subwoofer plug (Peel back the carpet a bit to access it)
  8. Disconnect the 4 silver T15 screws labeled above as well, and twist the subwoofer out.
  9. That’s about it, I didn’t replace my seat rail bolts immediately… Appears as if the dealers have these in stock at all times. I’ll do that this weekend.

Extra notes

  • The torque for the 4 seat rail bolts is 42 Nm or ~31 ft/lbs
    • It’s a bit of a pain but don’t torque all the 4 seat bolts down until you get the bolts in each hole on the front and back. The rails have a bunch of play in them and you don’t want things getting all twisted up
  • If you removed the seat belt bolt, the torque is also 42 Nm
  • When the seat is disconnected it’s a great time to clean up under the seat and cleanup the subwoofer cover

 

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