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Can Someone Explain A/C Oil

Discussion in '6.9L IH & 7.3L IDI Diesels' started by adamsanders, Jul 25, 2020.

  1. Clb

    Clb Another old truck Supporting Member

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    Sounds like youtube rhetoric, got any statistics to back this up?
    i would love to get my ac running for next to free...
     
  2. riphip

    riphip Supporting Member Supporting Member

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    Never changed hoses on any of mine. No leaky
     
  3. adamsanders

    adamsanders Full Access Member

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    So I’ve now got the compressor off and drained of the old oil. I didn’t really notice or think about while it was on the truck but the side of the compressor housing had a fair amount of oil buildup. Any ideas on how to tell if this was the front seal leaking on the compressor or just oil and fuel being flung onto the side for 30 years? For what it’s worth, the oil was mostly concentrated on the side facing the engine. I would had to get it all back together only to have a massive leak on the compressor.



    47B17E0D-70D3-40EA-9D87-0675D81CF8CB.jpeg
     
  4. Booyah45828

    Booyah45828 Full Access Member

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    I've never heard of them being pickled before. I have heard that the leftover mineral oil in the system on the hoses and o-rings will act as a barrier against the new oil and refrigerant. For the o-rings and hoses to be pickled, they'd have to absorb the oil, and I don't really think that's what happens.

    In the mid 80's most oem's were already using neoprene o-rings and hoses. Neoprene is compatible with both r134a and r12, so there is no need to change them due to incompatibility. In a lot of classic vehicles they used nitrile, which isn't compatible with r134a, hence the need to change stuff. The problem is that there isn't a way for the average joe to tell which one they have.

    I don't change the o-rings because they're incompatible with r134a. I replace them because they're included in the kit and are a typical source of leaks.
     
  5. chris142

    chris142 Full Access Member

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    those fs6 compressors always leak from the front seal. They even have a wick! When they leak that much with R12 they will really dump 134.
     
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  6. adamsanders

    adamsanders Full Access Member

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    Ahh. That’s what the “felt” piece is lol. Is that acceptable leaking then?
     
  7. franklin2

    franklin2 Full Access Member

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    "pickled" was just a term I made up. Barrier, whatever you want to call it, but it keeps hoses and o-rings that should leak with r134a from leaking. I have never heard of the ester oil or r134a "scrubbing off" any type of coating or barrier, so I would think this barrier would be penetrating some into the material of the hose and o-rings. But again, that is me talking, I am not sure exactly what happens.

    I have had hoses leak also when doing a swap. It looked like it had some sort of disease and had these wet spots all over it. Time for a new hose.

    The r134a is so cheap, it's not like you can't experiment and try things. If something goes wrong, fix it and try again. Like with the compressor above. It may leak, it may not. Put a conversion kit in it, if it leaks out and it's the compressor, then it's time for a new or rebuilt compressor. Pour a little ester oil in the new compressor, stick it on there and try it again.
     
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  8. Booyah45828

    Booyah45828 Full Access Member

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    A lot of compressors leak from the front seal. That's the only seal in the system with moving parts so it makes sense. Yours isn't terrible, but if it's obviously leaking I think I'd do something about it.

    You can buy a shaft seal and gasket kit pretty cheap. I'd try that before I'd replace it with another compressor. Make sure to clean/polish the shaft where the seal rides. I see on a lot of seal failures where that surface isn't good.

    Like franklin2 said, R134a is cheap. The hand grenade cans are like 5 bucks a piece, and if you're doing it yourself, you can trial and error things and be out very little. If you're paying someone to do it, then it's a different story, and trial and error gets expensive.
     
  9. Garbage_Mechan

    Garbage_Mechan Garbage Mechanic

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    My 91 compressor leaked about that much for the last 15 years. A can of gas every spring and good to go. The only problem was I didn’t think about replacing the oil that leaked out and made that crusty little mess. So it locked up. A couple new hoses, drier, and a used reman parts store compressor (from a parts truck I had) with a good flush 3 years ago and going strong no leaks. Charged with Duracool before and after.
     
  10. franklin2

    franklin2 Full Access Member

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    He's right, you need to clean up where both sides of the seal sit. But if you didn't know, this is not a conventional seal like you would think. It is a ceramic seal, much like industrial waterpumps use. It has two halves. both have polished ceramic surfaces with rubber around them. One ceramic side sits home in a cavity in the stationary housing of the compressor with rubber around the OD, and the other side pushes onto the shaft with rubber around the ID. There is usually a spring that presses the two ceramic pieces together to create the seal. The two ceramic pieces rub against each other, creating the motion part of the seal.
     
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  11. adamsanders

    adamsanders Full Access Member

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    My seal kit will be here today. I noticed it is a two piece design so hopefully I can it get in without much fuss. What should I polish the shaft with? I assume scotch brite would be too rough?
     
  12. Garbage_Mechan

    Garbage_Mechan Garbage Mechanic

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    The portion of the seal that touches the shaft (and housing) do not move there. The seal is made between 2 parts of the seal itself. So the shaft surface needs to be clean and shiny but not super critical surface finish.
     
  13. adamsanders

    adamsanders Full Access Member

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    So a little update.

    The clutch would NOT come off. I tapped and pulled for hours. Ultimately I wound up accidentally putting a screwdriver through the center part and trashed it. I could have cut it off at that point but i figure I would just go with a new compressor from Rock Auto. Got that installed along with flushing everything throughly. Pulled a vacuum for about 3 hours and unfortunately it wouldn’t hold a 30mmHg vacuum. After about 30 mins it had risen to 20 mmHg. It stayed there indefinitely. I’m not sure where to go from here though. I believe I have I leak but I don’t know how to find it in an unpressurized system.
     

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