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Thread: A/C - Why does my expansion valve leak? 8501 - 92

  1. #1
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    A/C - Why does my expansion valve leak? 850 - 92

    About 2 years ago I changed the expansion valve and the evaporator. All the o-rings was also changed. As I then refilled the system everything was fine, no leaks. Actually before refilling I checked the vacuum and it held for over 1 hour without any change (leak). Now 2 years later all the R134a is gone, actually all of it (1500 gr of 1880gr) blow out though the expansion valve rather suddenly, but why? I remember that I could hear the R134a when it expanded after the expansion valve when the system was refilled. Don't know if that means anything, this is my very first 850 so I have no reference to refer to. I do remember thou that when working on the A/C system I had to mount and dismount the components several times before getting it all correctly mounted, but it was leak free when I first checked it and it worked well for over 1 year at least. As I understand the pictures it is the lower part, the underside of the expansion valve where the leak is all thou there is some splashes on the thicker tube on the upper side under the clamp. The oil with the UV tracing colour has been splashing and then dripping/running on the inside of the cover (no pictures) to the bottom. I don't know how it came to be on the outside of the rubber hose drainage but I remember that I got some water on the carpet once.

    PICT0004.jpg

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    Last edited by peake; 08-21-2018 at 05:59 AM. Reason: Error in titel

  2. #2
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    Did you replace all of the O-rings in the system?
    I just did the expansion valve replacement on an 840 a few weeks ago. Replaced the expansion valve and purchased a new Dryer/Accumulator (always replace this when you crack open the system). I flushed the condenser and the evaporator and replaced all of the O-Rings. Car is as cold as a freezer now.
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  3. #3
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    The O-rings were new, I changed the rings about 2 years ago. I gave up this time and went to a A/C specialist. He pressurized the system with nitrogen gas, performed a leak test using a tester. He didn't find any leakage at any joints any where in the system. But he found out that the temperature head on the expansion valve had a small/minute leakage. This leakage was not obvious when testing with vacuum since then the outer air was pressing against the head and tighten the leak.
    As I mentioned earlier in this thread there was some 300 gr of refrigerant left in the system, enough to keep the system going producing some but not much cold air and not to much pressure to let the 300 gr of refrigerant out.

    By the way, the sticker on my car says that the A/C system need 1800gr +/- 25 gr of R134a but not how much PAG oil. Does anyone know how how much oil there should be?
    Last edited by peake; 09-16-2018 at 08:58 PM.

  4. #4
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    The changeover from R12 to R134a was made in September 1992 - and the filling capacities were:

    R12: 1925g of refrigerant and 200ml of PAG oil
    R134a: 1550g of refrigerant and 160ml of PAG oil (Denso compressor) / 180ml of PAG oil (Seiko compressor)

    Full info here:

    https://www.meeknet.co.uk/gen_bmw/BM...nditioning.pdf
    Timm..2007 E64 650i Individual Sport..1999 E31 840ci Individual Sport..ex owner of 2000 E38 740..1999 E38 740i V8 M62..1998 E38 735i V8..1993 E32 730i V8..1988 E28 518i


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  5. #5
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    Thank you, Timm so I noticed when I checked your excellent site. But my car is manufactured 9/91 (Vin: cb09186) which makes it to be a model 1992, manufactured 1 full year earlier before the change over. Also it has stickers from the factory saying R134a and 1800+/- 25 gr. This is not in your list, not pointing any fingers. I cannot find any information anywhere saying 1800 gr. I wonder if it is safe to assume that saying that the amount of PAG-oil should be 10% of the weight of the refrigerant 1800 gr --> 180 mL of oil.

  6. #6
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    That sounds more like an R12 system that was modified to run R134a with a compressor change - hence the strange capacity. It might well have been done at the factory but it would have started life as an R12 system. 180ml of oil will be fine.
    Timm..2007 E64 650i Individual Sport..1999 E31 840ci Individual Sport..ex owner of 2000 E38 740..1999 E38 740i V8 M62..1998 E38 735i V8..1993 E32 730i V8..1988 E28 518i


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  7. #7
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    Assuming that you are right, Timm. The car was originally manufactured for the German market. When I bought it 2014 it had been in storage for more than 6 years and I had to change the A/C compressor since it did not work. With the compressor there was a control box, sitting under the A-pillar that also was changed. I guess that this new compressor and the control electronics is designed for the refrigerant volume that you are talking about (1550 gr + 160 mL PAG oil). This means that there is 250 gr too much refrigerant in my system right now which can cause a to high pressure in my A/C and maybe did blow my expansion valve!

    Some things I noted when working with the A/C system.
    As I did mount the expansion valve onto the evaporator I had to turn the 2 x M5 Allen bolts about 1/4 to 1/2 turn each until the clamping piece was evenly pressed onto the expansion valve body making sure that the o-rings was evenly pressed. The other tube part (5)* fitted easily if inserted from the back and towards the firewall in an upright position.

    */ RealOem part designator.

  8. #8
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    Today I went to an other A/C service guy. He emptied the system using an special machine. Out came the following 2035 gr refrigerant and 225 mL of oil. He then recharged the A/C system loading 1550 gr of R134a and approx. 110 mL of oil. He claimed that when evacuating the system there is always some oil left in the system, about 50 mL. Since I'm not an AC specialist I don't know if this is so, therefore I ask you guys out there, does it make sense?

  9. #9
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    Quote Originally Posted by peake View Post
    Today I went to an other A/C service guy. He emptied the system using an special machine. Out came the following 2035 gr refrigerant and 225 mL of oil. He then recharged the A/C system loading 1550 gr of R134a and approx. 110 mL of oil. He claimed that when evacuating the system there is always some oil left in the system, about 50 mL. Since I'm not an AC specialist I don't know if this is so, therefore I ask you guys out there, does it make sense?
    makes total sense.
    you should keep this AC guy.
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  10. #10
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    Two weeks ago, I had to replace my evap coil/expansion valve. One thing I noticed when fitting the double pipe to the top of the expansion valve with the clamp you referred to was the bolt seemed a bit long. It’s possible that it was just so on mine but I thought there was a potential for the bolt to actually bottom out in the expansion valve. So, I added another washer for spacing to ensure that clamp firmly and evenly pressed down of both pipes. My clamp, and I believe yours also, is made of aluminum which of course is a pretty soft metal. I also checked it closely for any wallowing or bowing to make sure pressure was being equally applied to both pipes. It's kind of a balancing act with aluminum, too tight, you pull the threads out and too loose, there goes your coolant.

    If you're going back in there I'd suggest maybe ordering a new clamp, bolt and possibly a new double pipe. Many here have already said, and I whole heartedly agree, you d@mn near have to be Houdini to fit in there to work. I know I don't want to do mine again!

  11. #11
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    I meant the clamp on the underside ov the expansions valve. But you are all correct, the clamps must be flat. I had new clamps on both sides.

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