Coolant drain plug-engine
 

Mercy.... is it just me or is the coolant drain plug on the block impossible to get a socket to on a 3.0? I've searched and read several posts about coolant change but no one seemed to be unable to drain the block in addition to the radiator. I did remove the right tire but even with over 23 inches of extensions I can't gain straightaway access. How much coolant is really in the block and is it necessary to drain also? I bought BMW coolant and since I'm not the original owner I want to make sure the truck has the proper coolant and maintenance. And who knows when the last change was.

Thanks guys

Out poured......Orange! Hopefully it's Xerex G05 I think it's supposed to be amber in color.. But beautiful blue genuine BMW coolant went back in.

About a gallon drained from the radiator; I refilled, removed the bleed screw, and started the engine and out pumped about a quart of orange from the engine. I topped off, ran the engine for a bit, let cool, and re-drained the radiator then refilled again for a simi-flush/coolant change.

I'm planning on doing this next year, but from what I remember, you need 2-3 feet of extensions, plus a 13mm wobbly socket, like this:
FSUM13A, Socket, Metric, Universal, Shallow, 13 mm, 6-Point

You have 2 gallons of coolant in your engine. To properly take out the orange stuff, you need to take out the engine block drain plug as well, then open up the 3 hoses that go into the firewall - to the heater core. For best results, you can use also some compressed air at minimum setting. Then flush the engine with water 3-4 times, until there's no more orange tinge. Than, use a new crush washer for the engine block drain plug and tighten to I believe 25Nm. Then fill up with new coolant and observe the BMW procedure to bleed properly the system.
For now you just mixed 50/50 the orange with the blue coolant. You can see this if try to let some fluid go out through the radiator - it will be a weird color.

The gallon I drained after I added the BMW coolant was quite blue but with a faint aqua tint. Then after the second gallon that should make it 75/25? I have enough for 2 more gallons so I could get it to around 5% orange. If a 3 foot extension with wobbly socket is needed for the drain plug surely it wasn't designed to be drained. Seriously. It must be for if the engine is removed?

I repeat again: to drain ALL the coolant, you need to remove the engine block drain plug. Item #4 in the diagram below (p/n 07119904539) and replace the gasket ring item #5 (p/n :07119963200). Also, you need to drain the heater core. Ask me how I know (AMHIK).

http://www.realoem.com/bmw/diagrams/k/z/75.png

That drain plug is IMPOSSIBLE to remove even with a 3 ft extension and wobbly socket; good grief what if break/strip the drain plug? Then what. I think I might attach a hose to the bleed outlet, start the engine while I fill the expansion tank as it pumps out.

I know I did it on my e39 without a problem. I had to pull out the underbelly pan to reach it. It's between cyl 5 & 6 if I recall correctly. I used a wobble adaptor & extension, no problem. My X5 is the 4.4, so it's a different layout but for all intended purposes, once the steel plate is out (which is not hard to take off), you should have a clear shot at the drain plug. I just finger tightened the plug for the next 3-4 water flushes (garden hose), kept the heater core hoses on/off as I filled/emptied the system, and also used compressed air at very low pressure. Once the fluid stopped coming out, and I used the compressed air, another 1/2 - 1 qt of fluid would squirt out.
Really easy once you get in the groove.

If you are uncomfortable removing the drain plug for whatever reason, your approach will suffice as long as you add fluid and then turn on the heater and let it run for a few minutes and then add more fluid until it is very difficult to tell the difference in color of what is coming out and what you are putting in. The primary reason to change fluid is that over time the fluid becomes corrosive so removing the vast majority of the old fluid solves that issue.

I cycled two more gallons and the last drain was much more blue in color than the previous that was a light teal. In the near future I'm going to buy another gallon and cycle two more times and then it should be almost if not 100%.