Thanks for sharing this. Important topic that is often ignored by people.

I always:

1. Use 2 jack stand under subframe: one 4-leg jack stand + a screw-type jack stand. Once the car is lowered on to the 4-leg jack stand , I used the screw-type jack stand and nudge it up a bit. This way the load is shared by 2 jack stands. I post photo of this setup in bimmerfest E39 forum.

2. Always chock the diagonal opposite wheel. If you do brake work on RF wheel, then chock the LR wheel: both the fore and aft parts of the tire.

3. When using drill, air tool (hose can burst), looking up at chassis from under the car, or any job that stuff can fly into the eyes, I wear goggles!

4. Always wear work gloves when dealing with ratchet, breaker bar. The potential for slipping is there as you learned just now. Always make sure the nut/bolt head is in good shape, if not, it can slip. Make sure the socket sits nicely in the bolt head! Check to be sure it is the proper socket, don't use a 22-mm socket in a 21-mm bolt! It will slip...

If possible, push the breaker bar AWAY from you. If you pull it toward you, have a plan B ready "what if it slips, where does it go...hopefully not the lip or nose or eyes".

(Well, many years ago, the breaker bar slipped and it hit my chest, right on the sternum, it hurt like h#ll...).

5. Always have a cell phone nearby...

6. Watch out for earthquake if you live in that zone.

For every job in car repair, there is always a precaution, the best defense is the internet, look up the potential hazard of any job (whether it is brake pad or coolant change etc.) beforehand, and you will be happy you did!

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1998 E39 528i 5sp MT
2006 E53 X5 3.0 6sp MT