R12 System - Evacuate or not? - Page 3 - PeachParts Mercedes-Benz Forum

ttownthomas · #1 02-24-2018, 01:01 PM

Here is my plan:

I want to keep running r12 but I need to fix my leaks and replace all the seals first. but before any of that I want to see if the system is functioning correctly.

I want to pull a vacuum on the system and then fill it with 152a and dye to find all my leaks AND test the rest of the system.

What do I do about oil with the 152? Should I check the level at the compressor when it is empty? Just add a little for good measure? What oil should I use?

Diseasel300 · #2 02-24-2018, 02:04 PM

If you change refrigerants, you need to flush the system and refill with PAG oil. 134a and 152a both require PAG oil. R12 uses mineral oil. The importance comes with how the oil circulates, R12 is miscible in mineral oil, so it is carried along with the gas charge. 134a and 152a are not miscible in mineral oil, so it will not carry it through the system. You run the risk of starving the compressor for oil, or oillogging the condenser or evaporator.

If you're sticking with R12, stick with R12. I did that originally in my SDL, but after about a month and a half of use, the expansion valve got stuck open and stopped cooling. You can't buy a new R12 rated expansion valve (different orifice size than R134a), so I converted the system at that point. When the conversion is done correctly (flushed, filled by weight, correct expansion valve) there's not much difference in performance on these later W126's. Early 126's and the W123's had a crappy condenser that was barely adequate for R12. The Gen II's have a small-tube double-circuit condenser that's much more efficient with the newer refrigerant. The SDL cools just as good if not better than most modern vehicles in my climate and I don't even have the windows tinted...

ttownthomas · #3 02-24-2018, 02:09 PM

Quote:

Originally Posted by Diseasel300

If you change refrigerants, you need to flush the system and refill with PAG oil. 134a and 152a both require PAG oil. R12 uses mineral oil. The importance comes with how the oil circulates, R12 is miscible in mineral oil, so it is carried along with the gas charge. 134a and 152a are not miscible in mineral oil, so it will not carry it through the system. You run the risk of starving the compressor for oil, or oillogging the condenser or evaporator.

If you're sticking with R12, stick with R12. I did that originally in my SDL, but after about a month and a half of use, the expansion valve got stuck open and stopped cooling. You can't buy a new R12 rated expansion valve (different orifice size than R134a), so I converted the system at that point. When the conversion is done correctly (flushed, filled by weight, correct expansion valve) there's not much difference in performance on these later W126's. Early 126's and the W123's had a crappy condenser that was barely adequate for R12. The Gen II's have a small-tube double-circuit condenser that's much more efficient with the newer refrigerant. The SDL cools just as good if not better than most modern vehicles in my climate and I don't even have the windows tinted...

By "flush the system" you mean take it apart and flush all the parts manually? No reason not to replace stuff at that point. Are their quality aftermarket parts or will I need genuine MB parts (reciever/dryer & expansion valve) for this?

Diseasel300 · #4 02-24-2018, 03:22 PM

Flushing the system involves opening up the lines and sending a flush solution through it. It isn't difficult. You'll want to drain the sump of the compressor too.

After flushing, replace the O-rings, pressure switches, and receiver/dryer. There are decent aftermarket parts out there. Modern replacement parts are designed for the pressures and lubricants used in 134a systems, just another reason to convert it if you're going that far.

Hit Man X · #5 02-24-2018, 03:34 PM

FWIW I ran the 300E on mineral oil and 152A until it met its demise New Years Eve. That was three years worth on the original compressor.

You would be fine to charge it and get it cooling.

ttownthomas · #6 02-24-2018, 08:32 PM

Quote:

Originally Posted by Hit Man X

FWIW I ran the 300E on mineral oil and 152A until it met its demise New Years Eve. That was three years worth on the original compressor.

You would be fine to charge it and get it cooling.

If I charge it with 152 and then evacuate again will I contaminate somthing?

Hit Man X · #7 02-27-2018, 11:45 AM

Well, if you evac it into a machine with 134A, yes. You will destroy their recovered refrigerant...but seeing as how 152A comes in air duster cans, you can just release it into the atmosphere and it is no big deal.

Initially I had 134A in that 300E as it was all I had on the shelf. It leaked out, so that is when I tried the 152A. Cheaper and worked better. R12 would be better, but for $15-30 for a 12oz can versus $2-5 in...it was a no brainer for me. The car cooled very nice for me.

Make sure the condenser and radiator are clean. Need to pluck the rad to pull the condenser far enough back to pull the dual aux fans. It is worth the hassle. Also, the only fan clutch that worked for me on the M103 was the Sachs. With no air flow over the condenser, you will have weak AC always.

ttownthomas · #8 02-28-2018, 01:16 PM

To educate myself and to be able to buy R12 I went ahead and got 609 certified. It was easy. I read the booket (about 60 pages) and took the test.

I have decided that putting R152a is not worth the risk. Perhaps the EPA is being over zealous but they feel that it is a safety hazard to run it in a system that runs the R152a through the passenger cabin. Apparently it is flammable under certain conditions.

I figure Ill just run it the way it was designed. From what I have read I think the compressor on these things is supposed to run all the time unless:

1. The AC is switched off
2. The high pressure side is below about 40psi (mine was at 50)
3. The receiver dryer gets over a certain temperature

Plus my pulley does not "retract". It either spins or does not spin so they must have changed compressor designs at some point in the life cycle of the W126.

Anyhow. I charged up my system with my 2 cans of R12 freon and injected some dye in the system. Presto - Cold air.

Now Ill watch for the dye and how fast it leaks out and then Ill repair the leak and evacuate and recharge with a fresh R12 charge by weight.

MCallahan · #9 03-02-2018, 10:20 AM

The stop leak freon will kill your compressor. The leak is usually shot compressor seals, anyway. New compressor isn't crazy expensive and you don't have buy a MB factory unit, as they are an OEM manufacturer part. If you see green dye on the back side of the pulley, plan on swapping the compressor before it blows up and sprays metal into the whole system.

Diseasel300 · #10 03-02-2018, 10:29 AM

The stop leak will also kill the expansion valve if you have any air or moisture contamination in the system. When it goes, plan on converting to 134a, the modern 134a expansion valves have a smaller orifice size than the R12 ones did and they're all that's for sale.

Hit Man X · #11 03-02-2018, 12:59 PM

I have used leaking compressors for YEARS on various vehicles. They do not just blow up at random. They seize when the system has very low/no refrigerant as the gas moves the oil. Keep it full and it will keep running.

Even my dumbass R4s on the SD were like this that had no sump. Now I have a Sanden from Klimakit and I will never run a 617 again without a Sanden on it.