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Old vehicle ac system

Matt783 on Tue June 30, 2015 3:07 PM User is offline

Year: 1987
Make: Toyota
Model: 4runner
Engine Size: 2.4l
Refrigerant Type: R12
Country of Origin: United States

My truck hasn't had working ac since I bought it, there isn't any pressure in the ac system, at one point I replaced the cylinder head and I had to displace the compressor to do that, I don't remember if I did take the lines off or if I left them on an just displaced it, either way right now it's totally empty. I would like to get it working, I have done ac work on other vehicles, but I'm not sure where to start with this one. Does the dryer have to be replaced? And would the oil have stayed in the system, or would it all escape with the freon? Can I get by with just adding some more oil and vacuum it down to see if it leaks, or am I going to have to flush the whole system? I am planning on keeping it r12, I have a few cans of r12 in my garage.

Matt783 on Sat July 11, 2015 2:12 PM User is offline

I'm planning on replacing the drier, and adding 4-5oz of mineral oil to the system to make up for the oil that probably escaped with the old refrigerant. Then vacuum it down and see if it holds to check for leaks. And if it holds charge it back up, does this sound like a good plan? Also should I add all of the new oil to the drier, or half in the drier and half in the compressor?

mk378 on Sat July 11, 2015 4:24 PM User is offline

1. Before taking anything apart, do a static pressure test to try and identify any leaks.
2. Oil generally stays in place as refrigerant leaks out. Too much oil is bad. Stale oil is bad. It would be good to at least remove the compressor from the truck and drain it, then put back the same amount of new oil.
3. Replace any o-rings that you can easily, especially on the line from the compressor to the condenser. That line runs hot and the o-rings are prone to harden and leak. Also of course address any leaks found in step 1.
4. New drier.
5. Both vacuum test and static pressure test again. Always use some other gas to confirm that an R-12 system has no major leaks under pressure before charging with R-12.
6. Evacuate and charge with R-12.

Matt783 on Sun July 12, 2015 1:39 PM User is offline

Just took off the compressor, and it was bone dry, also the drier was bone dry and all of the lines I took of were as well. I'm wondering if their is any oil in the system at all, how much do you think I should add? And where should I add it?

Matt783 on Mon July 13, 2015 7:50 PM User is offline

I have to get this back together tomorrow, I'm guessing their isn't any real way to know how much oil to add, what would be the best way to guess? Or maybe I could just add the minimum amount of oil the system could function with, assuming their is a little still left in it. Or do I really need to flush it? Can I flush the lines evaporator and orfice valve at once, or would I need to take it all apart, because that would be pretty involved.

HECAT on Mon July 13, 2015 9:44 PM User is offline

The lack of oil found may indicate it all went to the evap. As the refrigerant leaks out, the oil migration back to the compressor slows, and it pools in the evap. With a system non operating for a long period of time, it may have congealed into a oil tar. IMHO, It should be flushed.


HECAT: You support the Forum when you consider for your a/c parts.


Matt783 on Tue July 14, 2015 7:41 PM User is offline

Took the evaporator out today, couldn't get any oil out, the inside of the lines look really clean. I'll flush the system this weekend and put it back together.

Cussboy on Wed July 15, 2015 2:19 PM User is offline

Originally posted by: Matt783
Just took off the compressor, and it was bone dry, also the drier was bone dry and all of the lines I took of were as well. I'm wondering if there is any oil in the system at all, how much do you think I should add? And where should I add it?

I have an R-12 system on my 1988 Mazda truck. Last October the compressor seized suddenly on the way to work, it had worked fine Sunday evening (in Phoenix one uses the AC in October). I bought a new compressor from board sponsor AMA, picked it up in person. I actually had thought before this that the compressor seal might be throwing a little oil.

I also found that my old compressor was bone dry, and it was an 11-year-old rebuilt unit from AMA, and I hadn't added any R-12 in that time, and wonder if it's even possible to lose refrigeration oil but still be OK on refrigerant and cooling?

Anyway, I did flush the serpentine condenser and add a new receiver-drier. The new Sanden 708 compressor did not contain oil. And - related to your question - I added the full amount of R-12 mineral oil to the compressor (about 6 ounces in my case) and after I bolted it on I rotated the compressor hub several times to get the oil out of the compressor cylinders before I evacuated and filled with R-12. So mine's doing fine in the Arizona summer.

Matt783 on Tue July 21, 2015 9:39 PM User is offline

So I finally got it flushes, replaced all of rings and put it back together, did a static pressure leak test and a vacuum didn't find any leaks. Got it charged up, seems to work pretty well could be a little colder, high side pressure is around 210 low side around 35, maybe a little overcharged? I also have found that I have a leaking shreader valve on the high side port, the plastic cap seems to be holding pressure for now, but I doubt that's a very permanent fix, do the make metal selling caps, so I don't have to replace the valve?

Matt783 on Thu July 23, 2015 11:42 AM User is offline

Got the shreader valve changed, a buddy of mine had the tool to do that without letting the freon out. Do the pressures sound good, or do you guys think it's overserviced? The took the readings at about 2000 rpms and 100f

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