Those lines can only be acessed by removing a cover panel in the cargo area that is just behind the rear seat (search the forum and read, it's all in here). I would not trust a brake shop with that system or, for that matter, the interior of my car.

BTW, if your ride is good but the rear sags, you probably have a positioning valve issue. If the linkage or connection to the positioning valve is loose or adrift, the ride height will not be adjusted properly but the ride quality will probably be OK.

Once again, do the searches, read the content. It's all here.

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Never a dull moment at Berry Hill Farm.