Drain/Depressurize Front Air Springs from Rear Compressor?

[OnTouring]

Hi all,

I'm prepping for front air strut replacement on my 4.8is. I've found the DIYs here touching on how to deflate the front airbags and none mention a method to drain without damaging the existing (or leaking) parts.

When I did my rears I drained the air from the banjo bolts in the rear, up top, near the compressor.

I've also found this TIS guide for deflating the system.

My questions are

1- Is it possible to deflate the front bags by loosening the rear lines for the front struts? Similar to the process of doing the rear airbags? Will this be "safe" for the air system?

2- When, if ever, is a real "ride height calibration" needed by resetting via computer, on the front bags? Is this a near needless precaution?

[Omerta]

What damage are you concerned about?

Support the wheel at height before deflating the bags, should reduce the stress on them.

[OnTouring]

Originally Posted by Omerta

What damage are you concerned about?

Support the wheel at height before deflating the bags, should reduce the stress on them.

What concerns me is any unintended damage induced upon reinflation, to the air system, air system settings, or the new springs themselves, as an effect from improper deflation.

Some have reported puncturing the current bags to deflate for removal. This is a sound method, though one of mine is fine and will be replaced preventatively.

If there is a way to deflate by loosening the banjo bolts at the air reservoirs, like when doing the rear air springs, where are they on the fronts? Are they also near the compressor in the trunk, or are there banjo bolts at the front springs?

[richardb]

I would be curious to know if this could be done as well, but likely is done with INPA or specialized BMW software to deflate a particular corner.

Arnott said to lower the strut down (while inflated) and crack the air line fitting open which will bleed off the air on that corner. Seems sketchy to me personally, I haven't done it yet. I only have experience replacing an air strut on the driver side of my car which had already deflated due to aged rubber.

Here was the DIY video I made for that, maybe will give you an idea of what's involved with the brass fitting and airline in the strut housing:

https://www.youtube.com/watch?v=yW2NhlJ1ahM

[OnTouring]

Originally Posted by richardb

I would be curious to know if this could be done as well, but likely is done with INPA or specialized BMW software to deflate a particular corner.

Arnott said to lower the strut down (while inflated) and crack the air line fitting open which will bleed off the air on that corner. Seems sketchy to me personally, I haven't done it yet. I only have experience replacing an air strut on the driver side of my car which had already deflated due to aged rubber.

Here was the DIY video I made for that, maybe will give you an idea of what's involved with the brass fitting and airline in the strut housing:

https://www.youtube.com/watch?v=yW2NhlJ1ahM

Thanks for chiming in. I actually watched your DIY the other day!

I'll be taking on the 'deflate via the strut air line' method today, like what you mentioned from Arnott. Will report back with the end method.

One front has a slow leak, the other is still in great shape. Should be a confirming result.

[richardb]

Originally Posted by OnTouring

Thanks for chiming in. I actually watched your DIY the other day!

I'll be taking on the 'deflate via the strut air line' method today, like what you mentioned from Arnott. Will report back with the end method.

One front has a slow leak, the other is still in great shape. Should be a confirming result.

Haha good stuff! Let us know how you made out with it!

[OnTouring]

Originally Posted by richardb

Haha good stuff! Let us know how you made out with it!

Ok back with a remarkably exciting result.

Lower the strut, damaged or not, suspension filled. Crack loose the air line, wait. Continue on.

A note to anyone reading this on a serious note, take care upon reinflation to get the air pumping in them (battery back on, vehicle running) with jack still supporting full vehicle weight, wheels on the ground, until the system is filled (air springs pumped up taut).