I wanted to pass along my thanks to Shipkiller for his wonderful website. I have a 2003 Z4, and of course at 39K the top stopped working. Yes, just outside of the extended warranty BMW said they would cover. And since I do practically ZERO work at the dealers I expected my chances of getting the repair covered were nil, or maybe even less.
At 44K I decided I was tired of muscling the top up and down, and started getting the parts together to do it myself. I picked up a brand new motor off of eBay for $75 last winter (no one else bid on it, I put it a $600 bid, but got it for the minimum bid). The BMW parts catalog is confusing, so I was concerned that I had the wrong motor, but came upon Shopkiller's website, which showed the same motor as I had . I always say that I can take anything apart, and sometimes get it back together again. I had just finished replacing the evaporator on my Durango, which involved stripping it down to the firewall, so I was only a little concerned to tackle the mechanics of the Z4 problem. My bigger worry was doing a bozo and scratching the paint.
So after pouring over Shipkillers photos I tackled the repair. You really only need a second person twice. Once for 15 minutes or less to lift the disconnected top out of the car, and once to put it back in. All the disconnects and reconnects are really a one-person job, but it would be nice to have someone else keeping track of the order things came out.
All total time for the repair was 5.5 hours start to stop. 3 1/2 hours to take it out, 2 hours to put the new motor on and reinstall the top. I bet I could do it now in 4 hours total.
My comments that I would change/add:
1) Remove the switch first before removing the soft top compartment floor. It's easy to get at both torx screws. Why? Because when you put the compartment floor back in, it is real easy to knock the lever off the switch. I know, I did it. It's real easy to remove and reinstall the switch with the compartment floor back in place, so you might as well just take it out first.
2) Getting the soft top weatherstripping disconnect from the car is difficult to start, but easy once you get started. You have to start from one side or the other, and work all the way around. Don't start on one side stop in the middle, then go to the other side and end back in the middle. What happens is the aluminum in the seal will get a reverse curve, and you'll curse and have to work it with a soft mallet to get it to reseat.
All total cost for the repair? Under $200. I bought the motor on eBay for $75 (alright, I realize I lucked into that and it won't be typical), I bought the new housing and insulation from ecstuning.com ($103 including shipping), and $7 for a tube of silicone plus some butyl tape.
So all in all a relatively easy repair for a big amount of savings.
Steve
2003 Z4 2.5