Folks,
I’m getting the AC on my 83’ 300TD up and running again. When I bought the car, one of the suction lines had a hole, and the system was completely dry. Compressor was worn but not damaged (I’m replacing it anyway).

Today, I flushed everything out with 1.5 gallons of AC flush and my air compressor. The flush was running clear by the time I was done. I then blew the lines out with air.

However, I came back out in a few hours and swabbed the inside of a few lines with a q-tip, and some of them still had a little bit of greasy residue. More prominent in the discharge line.

I could try flushing again, but not sure this stuff will come off without mechanical cleaning.

Any ideas? I’m tempted to just run it, but don’t want to destroy my brand new Delco compressor.

Thanks in advance.

I should ad: I’m confident all loose debris is gone, and I plan to vacuum the system for at least 2 hours. It’s just this stubborn “patina”/stain on the inside some of the lines that is making me pause

Sounds like your on the right track. I just did this to my 85' 300TD last week. I replaced what looked like the original compressor, lord only knows how long the system had not been working. The foam around the expansion valve melted with the tiniest touch.

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85 300TD (169K)

Could just be varnish, largely inert. Most conservative bet is to replace the old lines (but only if you’re in deep on a serious rebuild). Delco eh? Bold move.

That said, if your lines blew clear and you’re pulling a long vacuum, not sure I’d lose much sleep over it.

So we are in the same boat! Yes, my system looks like it's been INOP for many years. How was flushing your system? Did you experience what I am?

Thanks Shern. Yeah, It's probably moisture and old mineral oil if I were to guess. My new refrigerant and oil are compatible with mineral, so the oil may possibly re-suspend. We shall see.

I don't plan to replace the lines, no. They are all in good shape other than this stuff on the inside.

Yeah AC Delco compressor! As far as I can tell, they are the best bet for reliability if sticking with R4. I have an older AC Delco compressor that has been great on my sedan for a long time.

I went thru three cans on NAPA Red AC Flush, and it was a mess that came out. Afterwards I used compressed air to dry out the lines.


The cursing started 45minutes into holding the compressor on my chest while trying to get it in place to thread a bolt, all this while the 2oz of newly installed oil dripped on me. The compressor had me feeling like a punk on the school yard as it pissed green oil onto me. All I could do was stay with it.

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85 300TD (169K)

Yeah, I saw your thread. How did you end up adding the oil after you installed the compressor?

Also, some updates:
-When looking closer, the contamination looks like greyish powder. It's very smooth.
-It comes off on a q-tip, but not on my finger.
-I found another thread that had my exact symptoms. In that thread some folks said it was oxidized oil, and would never come out with flushing. One user described it as "normal wear"

Now, a question: have any of you added additional filtration to your AC system? Like an in-line mesh filter? I am replacing my drier of course, but an extra filter would be nice.

Thanks all!

Thanks to the response from ah-kay, I was able to pick up a few cans of oil in compressed cans from Oreilys.
https://www.oreillyauto.com/detail/c/certified/certified-refrigerant-oil-3-ounce/int5/ec2v

Are you doing the R12 or R134a?
If doing the R134a you will need about 85% of what the R12 measurement is.

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85 300TD (169K)

I also added a different switch to the drier after watching several hours of youtube videos from "Woods and Barclay".
https://www.amazon.com/dp/B0066QPQ1K?ref=ppx_yo2ov_dt_b_fed_asin_title


This switch will allow the auxiliary fans to kick on sooner for better cooling.

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85 300TD (169K)

ACETONE! Skip the can flush, it's junk. Acetone cleans and doesn't leave anything behind and costs WAYYY less... Compressed air to "dry" out the lines is an oxymoron.

Thanks all, I was leery of using Acetone, so I just bought more and better AC flush, and flushed the system again. I bet I went through each part 3-5 times each. The system is currently holding a vacuum to check for leaks. I'll charge it on Tuesday, wish me luck!

I also decided to use this same switch. Do you happen to know at which temp it kicks on? Thanks for the link.

It turns on almost immediately. Takes less than 1min for sure.
I noticed while out this morning for groceries.

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85 300TD (169K)