1) fix above should do the trick. I would maybe use "canned air" vs. trimmer string. A little chewed gum or similar to make a tight seal

2) air springs can last 200,000 miles. I believe mine are Original at 197. That said wife's 2012 with 76 k has a leaky bag. I would spray them with AT-205 or equivalent to slow dry it (I also use on CV boots). I wouldn't replace preemptively since they are very easy to replace though I'd possibility consider having one on hand for the inevitable.

I think e53 have unique left and right but I thought I only saw one part number when I ordered for wife's E70. So I guess I'd just wait. They usually fail slow-leak and you can drive after it pumps up every day if needed.

3) The part to explode is the part you are replacing. Where is the leak exactly? The most common lower hose leak is the o-ring at the outlet temp sensor. I was out in the boonies at 1am when I noticed mine was leaking like crazy.

I pulled out the sensor, quickly stuffed a finger from a nitrile glove stuffed with paper towel in the hole. I wrapped 3-5 wraps of Teflon tape around the completely flattened o-ring and swapped the "finger" for the sensor with the idea of when I return to civilization I'd replace the o-ring.

That was 3.5 years ago. Never bothered to replace the o-ring as it never leaked since.

I am a big fan of the method of hose connections on the BMW, but they can be difficult to break loose and I've done my share (maybe 30-40) and the best way I've found to knock them loose is to start with a very large flat screwdriver (so the very end is maybe 1.5-2mm and after releasing the capture spring, use a small hammer and tap the screwdriver on the fastest part of the hose connector. Once you get it moving you will have an opportunity to get a small pry tool just inside the male side of the connector and you can pry there.

Of 30-40, I broke a 2x5 mm piece off the part where I pry but it was outside the o-ring seal and did not affect the connection.

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2011 E70 • N55 (me)
2012 E70 • N63 (wife)