has anyone ever replaced a fuel sender? I was wondering if there's a special tool needed to remove the "cap" on it. Bentley manual says that there is one, but I was wondering if anyone has used something different.

You will need either a large pair of channel lock pliers to remove the retainer ring or you can use a straight blade screw driver and small hammer to tap it off. It screws off. Youwill also need new hose clamps. 3/8" to 1/2" clamps. Make sure they are stainless steel.

Oh, do this in a well ventilated area.

I've already replaced the clamps. Got a fuel leak somewhere, usually after fillup. I noticed the barb on the return line has pretty much disintegrated. So Im gonna replace the sending unit.

one problem though, I just noticed that the sending unit I bought from bimmerparts, it might be for the left side only. Does anyone know if they are the same for left and right?

There are different units for left and right. The right side also has the fuel pump mounted in it. I don't know if it is integral or if the pump is a separate part. There is also a change when the OBDII system was installed. At least thats what I remember the dealer saying.

I had a crack in one of the hose nipples on the left unit on my 318. I had noticed that I smelled gas after running the car. It was like this for a few months and my MPG went down. But I never noticed a puddle form under the car. Then one day the smell got real bad and I did notice some drips while the car was running. The fuel would accumulate in the top of the sender unit. When I fixed that my gas mileage went back up (of course). I sure do miss 450 miles per tank. (if I remember correctly)