Rusty AC pipes

[4DSC]

Good day all,

I'm in the middle of doing my AC Solutions r134 conversion (just in time for winter, as one does). The AC has never worked since I purchased the car, so the system has been out of commission for at least 12 years. Before I started taking anything apart, I leak tested the system and found that the lower hose to the compressor had been punctured, probably by road debris. The AC solutions kit replaces that hose, so that's not an issue. However once I started to take the system apart, I noticed that the metal pipes that are meant to be reused with this conversion have some rust buildup, presumably from years of having a leak in the system. At least I'm pretty sure it's rust from testing with a magnet. The larger pipe in this firewall set seems to be look OK deeper down the barrel, but the smaller one is scaly as far as I can see with a flashlight. Similar story on the ones from the drier to the condenser.



So I went off to the junkyard to see if I could salvage lines from a better car (somehow 2 e28s had showed up in 2 months) and crossed my fingers, but alas one of them was even worse:


And the second set was slightly better than what's in my car, but not perfect, so I picked it up but still unsure how to proceed.

So, ultimately, I'm looking for some advice. Should I look for a better used set of clean pipes? Unfortunately the firewall set is predictably NLA (64531381673). Should I try to clean up the best set I have and reuse them? I had already bought one of those AC pipe flush kits that you use with solution and compressed air before discovering the rust. Contemplating filling the pipes in PB blaster or CLP for a while, maybe agitating with some kind of brush, and flushing them well with the AC flush kit. Thoughts? Last thing I want to do is ruin the brand new compressor, etc. Or if I'm on the wrong path, does anybody have a clean set of pipes they'd part with? Would also need a couple more leading to/from the dryer.

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[Shawn D.]

You'd want to soak/agitate them in EvapoRust or something similar (not PB Blaster, that doesn't remove rust), but my concern would be flaking plating.

[gadget73]

yeah the internal rust doesn't fill me with confidence. Having that break loose and jam the expansion valve would be my concern here. Can try cleaning it but unless you can pass something all the way through there to scrub loose any garbage all the way through I'd be looking for better condition pipes.

[4DSC]

Yea, maybe something like this "flexible pipe brush", probably in a couple of different sizes. If I take all the piping apart, I _think_ I should be able to reach all the areas inside. My only other concern is that the rust would have weakened the pipes enough that the high pressure would be a problem...
Will take some better pictures, grab some part numbers, and see if anybody has a clean set for sale in the Parts section.

[4DSC]

Following up with a semi-related question. Does anyone know what this white or black stuff is that covers one of the pipes? Seems to have been there from the factory despite how sloppy it looks based on the several cars I've looked at now. Is it to prevent sweating? And what should I use as replacement? Having a hard time figuring out what to Google.

[vinceg101]

Yes it is there to prevent condensation sweating and insulation.
I used this as a replacement, found it at my local hardware store or any Home Depot:

[4DSC]

Excellent, thank you!

[gadget73]

The silvery coating engine-side is also there as a heat reflector. No point in dumping engine bay heat into the AC.

[Ju@n]

Had that same rust on mine, I removed all the hard lines, pressure tested them, cleaned them thoroughly and it's been working for the last 5 years .
I remember I used IPA, an air compressor, and a lot of patience