Subject: Re: AC fix and correct R12 expansion valve? Author: Hitmanx : member since September, 2006 : 2630 posts Posted on: 2010-03-15 18:29:02

First off, I am a BIG proponent on utilizing R12 in these older cars. The system was designed for it. From compressor/pressures, condenser, evap core, etc. It is cheap and easy to find, the OPEN BOOK, ONLINE CERTIFICATION is a joke for places that demand you to be certified to purchase.

Next, your exp valve leak is probably just the orings, unless of course you replaced those already. The exp valve does not care what refrigerant runs through it. Pal of mine uses one with Freeze 12 and another used 134A in his car, yes I was sad they chose to go that route. Be sure to use NYLOG or the green style orings when you rebuild the system.

All crap from dealer for HVAC is stamped R134A probably for legality sake. R12 has ceased production here in the US long ago, but there are hoards of it around for sale... just look on craigslist or even feebay. Thanks to our buddy Obama in office and his highly successful Cash for Clunkers (I hope you sense sarcasm), even more vehicles are off the road that utilized R12... so there is even more of a glutton around. I buy it in the offseason in 30lb tanks. Price is a wash between 134A and R12 anyway per pound... seriously.

I rebuilt my A/C system in my 300SEL a few years back with 134A compressor/TXV among other stuff and I run it off R12... no problems. Hell, my 300SDL has been running a 134A compressor and R12 for creeping up on ten years. AFAIK the 134A certified compressors are just able to deal with the slightly higher head pressures that 134A runs.

You cannot easily drain the oil, you have to flush the system (which is smart for what you are doing, basically a refresh/fresh start). R12 calls for Mineral Oil OR a good synthetic oil only like BG FrigiQuiet. Choose the syn, it will let the compressor run cooler, quieter, and last longer. Oil capacity I would guess 6-9oz. Total capacity is around 3lbs.

For the '86 MY BMW changed up the system for more capacity to cool... larger condenser was one of those things. It is easy to spot with maybe 1/4" tubes? versus the earlier ones around 3/8" or so. This is a great upgrade on the cheap to grab due to the ability to dissipate heat faster (MB also did this starting for the '85 MY). The evap core also changed as did the expansion valve, but I would not worry too much about those... the big helper is the condenser. I would also get the M30B35 pulleys from any late motor, the crank will overdrive the A/C compressor at idle for better output and the smaller water pump pulley will cool better AND pull more air at low speeds for better output. I paid $20 for each condenser at a U-Pull-It type of place. If those are not avail, check with dismantlers and other such places.

Also, if you have not done so... pull the blower motor and flush the fins of the evap core out. They are full of shit after 25 years. This will help airflow into the cabin. And of course even a light tint job will help heat rejection as well as protect your interior from UV.




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12/1982 745i Turbo
09/1983 745i Turbo
10/1984 745i Turbo
06/1988 750iL
And about 10 other vehicles from Ford, MB, and GM.

• AC fix and correct R12 expansion valve? (url) - cjarvis 2010-03-15 13:07:04 (397 views)
  • That is one of the COMMON leak points... - johnhstein, 85-M6CSi, 85 745i 2010-03-15 18:32:31 (346 views)
  • Re: AC fix and correct R12 expansion valve? - Hitmanx 2010-03-15 18:29:02 (731 views)
    • I agree.. r-12 if you can find it or - johnhstein, 85-M6CSi, 85 745i 2010-03-15 18:34:08 (320 views)
      • Great advice.. - cjarvis 2010-03-16 12:00:42 (311 views)
        • Re: Great advice.. - Hitmanx 2010-03-16 20:51:11 (332 views)
  • Re: AC fix and correct R12 expansion valve? - limeyexpat 2010-03-15 16:22:45 (327 views)
    • Al Gore will unleash ManBearPig upon you! (nt) - Vern 2010-03-15 20:51:52 (295 views)
      • Re: Al Gore will unleash ManBearPig upon you! - limeyexpat 2010-03-16 09:46:33 (297 views)
        • Its not Al Gore or Eric I am worried about... - cjarvis 2010-03-16 11:13:28 (319 views)
          • Re: Its not Al Gore or Eric I am worried about... - Hitmanx 2010-03-16 20:40:55 (360 views)
          • Be careful.. no methane discharges allowed... :-) (nt) - johnhstein, 85-M6CSi, 85 745i 2010-03-16 11:50:52 (329 views)