I did this while I was replacing oil pan. It had been leaking a lot. I noticed 2 rough spots inside the hole where the sensor goes. They were almost straight lines from outside edge to inside edge of the hole. They were almost perfectly perpendicular to each other on right and left side of the hole. I almost thought it was intentionally there. But I took a scotch pad and smoothed it up. Might want to run your finger in that hole.
$1300? Are you sure that they just wanted to replace the crank sensor o-ring for that amount? It's a $10 part (at the most... probably more like $2) and 30 minutes of time if you follow the short-cut procedure linked in the first post. Maybe 2 hours if you go crazy and remove the front bumper and tilt the radiator off to the side to get better access.
Perhaps there was more they were planning to replace? Other work to do?
I just finished replacing my crank censor o-ring using the ratchet strap method described here so I wanted to chime in to add some information.
A while back I replaced the oil pan gasket after my dealer pointed out it was leaking. Of course, I had to put the car in service mode for the job and I REALLY wish I knew about the crank censor o-ring at that time since the leak was still there after replacing the gasket. It would take all of 5 minutes to replace the o-ring when the car is in service mode.
The instructions here didn't mention that the underbody panel (Part No. 51757201782) also has to be removed. It's easy - two phillips-head fasteners toward the rear and loosen the four 10_mm bolts under the bumper. The panel then slides out toward the rear.
Strap Attachment Points
My first choice for the attachment points of the ratcheting strap hooks were not good. I attached a hook to one of the holes in the frame beams that run down both sides of the car, but that was distorting the sheet metal. The hook attached to the location where the dog bone attaches to the engine was also causing problems by hitting and potentially bending the bracket for the frame-side of the dog bone. I ended up threading the strap through the engine mount and tying a couple knots to hold it there, which worked well for the front. I hooked the other end to a hole on the right rear axle trailing arm (a thick and very strong piece of steel that extends toward the front of the car from the right rear wheel).
When ratcheting down the strap, I was tightening it about as tight as I possibly could without any additional leverage. It has to be tighter than you might expect just to be able to get your arm in the space where the work is done.
Removing the Electrical Connector
There's no mention of detaching the electrical connector from the sensor, but if you didn't, you'd have to replace the o-ring by feel with one hand. That would be a lot harder than taking off the connector and pulling out the sensor, if not impossible. Unfortunately, taking off the connector is not straight-forward. There's a red locking mechanism that must first be unlocked before you can squeeze the back of the connector and pull it off. Fortunately there's an identical connector on the ignition coil on top of the engine that you can practice on first (the box where all the spark plug wires attach to).
Conclusion
Although this ratcheting strap technique saved me a lot of time compared to putting the car in service mode, I wouldn't call the job easy by any means. The sensor is very difficult to access, even with the engine pulled back, and most of the work you do has to be done only by feel and with one hand. This method also makes it impossible to clean the mess that the leaking o-ring created. If you want to do it right, put your car in service mode. If you're lazy like me, use the ratcheting method. Being good with your hands is required and being a contortionist will make it easier.
My 2005 R53 with 25000 miles did not leak until I started running 40 miles roundtrip commute at 60 MPH instead of 4 miles. The strap method worked great. The tip of experimenting with the ignition coil connector that is the same as the crank sensor was critical.
The only other repair I have had to perform on my MINI is putting hose clamps on the power steering reservoir hose.
