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One of the first jobs with the E39 is making sure the tailgate stays up. In BMW fashion they made a little cavity under the roof to hide the dampers rather than putting them down the side like everybody else. 

As you can see I have these little cavities that house the dampers. When I cleared one out and vacuumed as much crap as I could out of it I noticed a fair bit of rust. The cavity is bone dry, even after all that rain we had only a few days ago so I'm assuming that whatever allowed the moisture in is fixed but I'd like to treat the rust in there. 

I was thinking of just blasting it full of rust converter but I didn't know if this would be beneficial considering I can't actually get in there to prep anything. 

Maybe there's a better product? 

Thanks guys

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Me, I would clean it as best as I could, pressure pack brake cleaner is great for getting into tight spots, then liberally hit it with rust converter, then cover everything with underbody spray

Underbody spray hides most, it not all, sins 

In saying this, if you don't have rust converter and underbody spray on hand, then as stated, a liberal coating of fish oil for peace of mind, then never remove the cover to look there again

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Yes I'm going through a similar thing with my R33 with rust in seams due to dried out seam sealer cracking. After much research I settled on Penetrol. Read what it does and its done a bloody fantastic job for me. Pressure pack comes with a thin tube to get into hard to reach places.

So I removed as much as I could from both sides. The shop vac did a great job of clearing 99% of it. I got it all as clean as I could and then absolutely drenched the whole lot in the rust converter. Tonight or tomorrow I'll hammer it again. The cavity must be close to 400mm in length and surprisingly I was able to get it right to the back. 

I'll quickly reassemble and then pretend I never saw it. I'll post pics (for me to ignore later) soon.

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