BMW: removal of O2 sensor, 1997 bmw 528i, o2 sensors

Question
I have a 1997 BMW 528i with 4 O2 sensors.  I was able to change the two after the catalytic converter, but I am unable to figure out how to get to the two on the exhaust manifold. Do you know of any special techniques.  I have a couple of 22mm specialized removal sockets but they won't do the job.  Probably need a very specialized tool.  I'm about ready to give up.

Answer
Tom,
 Unfortunately I am still learning about the late models, I have considerably more experience with the older BMW's.  I recently perchased a '99 328is, which has the same engine as your 5-series.  I'm still learning about this car, so I dont know the details yet.  My car just threw a check engine light, and it was the O2 sensor(s).  The reason my car threw this light is because my Thermostat is stuck open, and we have had some cool weather lately, so the car doesn't get up to temp, this causes the ECU to override the O2 sensor(s) and in turn flashing the check engine light.  So if you have had some cold weather lately, and this light just went off, this could be the problem.  Double check the thermostat.   

 I dont know if you already bought your sensors, but Bavarian Autosport has the best deal on them (Bosch factory replacement) at $120.00 a peice.  That's the best I have found, but there might be other deals elsewhere.

 Have you tried getting to them from beneath the car?  I'm guessing so, since you changed the rear sensors.  I know that sensor's in the manifold are subject to high heat, this and water are the catalyst's for rust and corrosion.  Those O2 sensor's are probably held by rust, and I would soak the threads with WD-40 (lubricant) for 10 minutes or so, then try to break them loose.  You might have to use an open-end wrench on them, as I dont see you getting any "O2 sensor" specialty tools on there.

 Since you do you're doing work yourself, there are some very valuable sources for info:
 
 www.realoem.com - this is what the dealership uses to look up parts for you, now you can do it yourself!  Click on "enter" then it will ask for your vehicle information, your car is a E39 5-series Sedan (touring is stationwagon).

 www.pelicanparts.com
 www.bavauto.com        Both of these are great sources for info and parts at great prices.

 I will get back to you on the other info about the "tricks" of getting these O2 sensors out.

 Take care,
 Josh