I just replaced the upper radiator hose on my mom's 740il and I have no idea how much coolant to replace. I can't decipher the little diagram next to the cap. What if I filled it to the top on a cold engine? Not that I did that or anything. ;)

take it to a mechanic and he will hook it up to a gauge goes on top of the cap and measures the pressure

using a 50% mixture of antifreeze in the continental US is OK.

If topping it off just get close to 50%.

It will also need to be bleed to get the air out.

No big deal just a screw to remove and replace when the air is gone.

Then top off the reservoir with 50% antifreeze or premixed.

Later,

another question about coolent. my 735 runs hot, did the pressure check, everything ok, cleaned the radiator with a spray cleaner solution, meant especially for that, but it still runs hot. what can it be?