Front seat removal/replacement E92

[MTM]

M3'ers,

Looking for help/advice...am going to swap out my E92 front seats (heated) like-for-like. Anything special I need to know? Good/bad experiences?

Thanks. Did some searching with little success.

[deansbimmer]

If you're replacing like-for-like seats as you said, there's no tricks. First remove the four torx bolts then disconnect the electrical and the seat comes out. Not really worth a DIY.

Do the swap with the key/car off.

[MTM]

Thanks. Was hoping it was that simple, but did not know if there was any sort of issue related to disconnecting the air bags and connecting the ones on the new seats.

I don't suppose anyone knows the torque value of the seat bolts? Was planning to apply 1-1/2 gorilla grunts worth of tightness in the absence of any actual data.

[Motorius]

Hi. My passenger seat went off the rails because there was a can that got stuck under the seat. I got the can out and was able to remove the rear torx bolts. I can't access the front ones because the seats are all the way forward.

Is there a way to perhaps disconnect the power and properly force the seat back so that I can access the front bolts? Is there a better way to resolve the problem?

[deansbimmer]

Originally Posted by Motorius

Hi. My passenger seat went off the rails because there was a can that got stuck under the seat. I got the can out and was able to remove the rear torx bolts. I can't access the front ones because the seats are all the way forward.

Is there a way to perhaps disconnect the power and properly force the seat back so that I can access the front bolts? Is there a better way to resolve the problem?

The seat rails are a captive assembly, I don't know how you would have managed to get them to derail so more details or pics would be needed to know what exactly happened.

The seat moves back and forth via a jack-screw type mechanism. The only way to get the seat to move back and forth is by rotating the motor's flex shaft pinion that connects to that screw shaft inside the rail. Very difficult to do in car with limited access. You're going to have to see what exactly happened to your rail and MacGyver a solution.

[Motorius]

I'll update with pics.

I went to the dealership and they wanted $160 to diagnose the issue. The warranty expired in July. They suggested that I may need a new seat motor.

Think of the seat as a tank with a left and right tread. Only the right tread is moving. Are there two motors? If so, I can see how one may be dead. If there's only one motor powering all of the movement, it makes no sense for them to say that the motor is dead.

[deansbimmer]

There is only one motor for the forward/aft movement. Its motor has two flex shafts coming out from the motor at each end connecting to the tracks. If one of your tracks bound up with debris then it's most likely that the shaft either stripped out at the motor or at the track. The shaft itself is only about 1/8" in diameter inside its guide tube.

[Motorius]

Thanks for the feedback thus far.

I did some research and I took a pic. It looks like the single motor drives two cables, one for moving the seat along the right track and one for moving the seat along the left track. Something must've dislodged the left cable. It seems that you cannot simply reinstall the cable. You can see the cable being held up by an index finger in the attached photo. It looks like a shoe lace.

I've read that I'd need to buy a group of parts that include the motor and cable. What some people have done is shave-down an Allen key to take the place of one of the cables. The motor turns the key and the screw drive turns so that the seat travels along the rails.

I have no confidence in my ability to make an Allen key shaft to use here.

[Motorius]

I found the parts on eBay. They were for the e36 so I had to modify a bit.

I got it working for a while but it seems that the left and right rails weren't synced in terms of being lined-up. That is, the left may have been more aft than the right.

Can someone post a pic of their passenger seat rails so that I can see how far along the seat should be on the right shaft in relation to the left shaft?