Is there an 02 sensor on my 1991 m3?

[bmw325is]

I was just wondering if there was one because if there is, I couldn't find it.

Also Is there a way to bleed the coolant system after you change the fluid?

[Bry]

Yes, there is an O2 sensor, and it should be replaced fairly often (I've read somewhere 50k miles). I need to replace mine, I haven't gotten around to putting in the new one yet. It is in the motor bay, on the exhaust, just down from where the 4 header ports connect into two. There is a cross section that looks like a H and the O2 sensor is right on the cross section. It sticks out, and the wire runs up and below the coolant tank.

To bleed the coolant system, just turn on the car, with the cap off, and let the bubbles work their way out, the system is designed to do it by itself. Don't drive around or anything though. Then fill it back up.