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need advise on 96 BMW 328i

dtom4 on Sat May 02, 2009 8:40 PM User is offline

Year: 1996
Make: BMW
Model: 328i
Engine Size: 2.8L
Refrigerant Type: 134
Ambient Temp: 65
Pressure Low: 50

Having been a lurker for some time I'm somewhat embarrass to ask. I just bought a 96 BMW 328i with a warm blowing ac. Previous owner said it needed recharging. The BMW site mentioned how easy it is with the kits commonly available in todays auto parts stores. Anyway I bought one of the kits with a can of r134 and a cheap LP gauge and charged up the system along with some pag oil. Got a LP reading of 30psi and started getting coolish air. Left it alone and today decided to top it off. While charging the compressor would cycle on for 2-3 seconds when pressure reached 50-60. Pressure would drop to 30-40, compressor would shut off and come back on again for 2-3 seconds after about a minute when pressure built back up to 60 or so. Kept doing this continuously. Air coming out the vents was about 60 degrees.
Then while I was poking around I noticed the top of the reciever dryer was wet. Looking closer I could see bubbling coming from the fitting for the line running to the expansion block. So now I know I have to evacuate the system and do it the way it should have been done to start with, the right way. I'm not sure exactly what to do though. I have access to a good vacuum pump and gauges. I'm thinking I should replace the reciever dryer, replace all the orings thats not too difficult to get to, I guess flush the they system, pull vacuum and top it off. Any suggestions on what to replace, procedures to follow, products to buy etc to get everything done? I'm not looking to go crazy here, just want the minimum needed to be done to get the system working as it should. Thanks in advance

Dave T.

Edited: Sat May 02, 2009 at 8:43 PM by dtom4

Chick on Sat May 02, 2009 9:47 PM User is offlineView users profile

Can't believe a BMW site would tell you to ruin your system with death kits.. Guess none of them are AC techs... Anyway, you need to recover the junk in there, pull a long deep vacuum and recharge properly, by weight, then you can diagnose it. Check for leaks, change the drier and expansion valve, O rings, If you flush the system be sure to add back the proper amount of oil before vacuum/charge.. You already know what to do, there isn't any short cuts to AC repair..hope this helps..

Email: Chick


Freedoms just another word for nothing left to lose

Matt L on Sun May 03, 2009 11:50 AM User is offline

I believe it, Chick. I see the same "advice" being given on M-B specific forums. There seems to be this idea that there really are shortcuts, but "the man" requires that we spend a lot of unnecessary money.

Turbine1 on Sun May 03, 2009 2:05 PM User is offline

I think you have identified the key points of the procedure. I would recommend you also replace the expansion valve while you have the system open. Its relatively inexpensive ($30 or so) but small particles of dirt can mess it up so its a really a must to replace it (along with receiver dryer of course) while you have the system opened up.
I just went through a similar project on my 1981 Mercedes (though I also converted from R12 to R134a) which had some major leaks after decades of use. If you are lucky it may be you just have a bad o-ring at the connection to the receiver/dryer, but you should replace all the seals while you have the system evacuated. If you are unlucky you may have junk in the system, so its really a good idea to flush rather than risk plugging the new expansion valve again, or worse, damaging the compressor later.
I am with Matt on the model-specific forums. I see a lot of good advice on other issues on the M-B and BMW forums but some occasional nonsense when it comes to AC.
Oh - and safety first - wear safety glasses while you are vacuuming and charging, keep your hands out of rotating belts/fans etc. , and double check all the connections before you do anything (if you accidentally connect your can of R134a to the Hi port via a gauge-set, which it is possible to do, the can is likely to go off like a grenade!)
Good luck,

Edited: Sun May 03, 2009 at 2:06 PM by Turbine1

dtom4 on Mon May 04, 2009 8:59 AM User is offline

Thanks for the input. Yeah I should and actually do know better but laziness got the best of me. My own fault. I don't have any maintenance history on the car but the leak at the drier is pretty significant. I can see it bubbling up. I'm thinking everything just leaked out and the previous owner never bothered with it. But who knows. I'm planning on opening up the system and replacing all the orings I can along with the drier and expansion valve, pull a long deep vacuum and if it holds charging it back up and hope for the best. I just ordered the parts from you guys today so hopefully by the end of the week I'll be cool again :-)


Dave T.

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