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E39 '99 528i AC Problems - Please help!

 
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Myron '89 325i



Joined: 02 May 2007
Posts: 34
Location: Houston, TX

PostPosted: Sat Sep 15, 2007 5:59 pm    Post subject: E39 '99 528i AC Problems - Please help! Reply with quote

AC started becoming intermittent and compressor started making noise - then died.

Old compressor shot. . .seized up - visible damage once removed.

Replaced Compressor, Drier, and expansion valve. Completely flushed each component in the system individually (not flushing anything through the compressor). Had the system recovered, vacuumed, leak tested, and recharged professionally.

Auxiliary fan works (variable speed).

Compressor kicks on for a few seconds until the high side pressure hits nearly 500 PSI, low side drops to about 70 PSI and then kicks off. When it kicks off, the high side pressure drops and the low side starts climbing. Once low side hits about 100 PSI, the compressor kicks back in for those few seconds and high side goes nuts. . .lather, rinse, repeat.

The pressure sensor is obviously working, since the compressor kicks off. I can see the aux fan kick in and work fine. Engine coolant temp is normal. Ambient temperature here in Houston is a muggy 95F.

Why does the high side shoot up to over 450 PSI almost instantly when the compressor kicks in? Is there a clog in the system somewhere? My flush didn't reveal anything clogged.

Please help.

Myron
'99 528i
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Myron
Houston
02 540i (working my way back up)

Past rides . . .
99 528i (got it back)
89 325i (now I'm legit)
99 528i (now I look like an adult)
02 M3 (dream car reality-er)
97 M3 (dream car reality)
97 328i (Now it's Bimmers for life)
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John Q Public



Joined: 08 May 2007
Posts: 17
Location: Hell...err...umm...Florida

PostPosted: Sun Sep 16, 2007 1:54 am    Post subject: it is possible... Reply with quote

it's quite possible there is some sort of debris cloggind the system...I've done A/C work on my own toys and in a couple shops I've run or worked...thankfully though I've not had to do anything to my bimmer except top-off the system in mine just before this summer (previous owner did an R134a conversion)...

BUT...(and I'm not sure if BMW uses them)...it's possible there is debris in the system from the failed compressor in an orifice tube...possible you have debris caught in the evaporator or condenser...or there is the off chance you actually have a bad expansion valve...

...seeing that the system was professionally tested...leak-down...and charge (I'm assuming they oiled...hopefully Ester and not PAG)...it'd set off a few warning bells that it's not working properly...was it a shop who works on BMWs???...did they know you cannot fill refrigerant in a BMW the same way you do an American car (done by weight of refrigerant not by low/hish-side pressures)...moreover...if they tested it properly it would have shown the same problems it's exhibiting before it ever left the repair bay...

just my two centavos...

Scott
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jlevie



Joined: 01 Jan 2005
Posts: 553
Location: Huntsvile, AL

PostPosted: Sun Sep 16, 2007 11:49 am    Post subject: Reply with quote

My guess would be plugged up expansion valve.
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edjack



Joined: 04 Feb 2002
Posts: 3887
Location: San Jose, CA

PostPosted: Sun Sep 16, 2007 2:37 pm    Post subject: Reply with quote

How did he recharge? The BMW method requires a slight overcharging, and then bleeding off refrigerant until the evaporator outlet temp is 3-4 deg C. The evap has a temp sensor that is read by the BMW diagnostic computer.

It sounds like you have too much refrigerant in the system.
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Myron '89 325i



Joined: 02 May 2007
Posts: 34
Location: Houston, TX

PostPosted: Sun Sep 16, 2007 8:51 pm    Post subject: Reply with quote

I replaced the expansion valve. . . and the old one looked clean to me.

And I did flush every component, using a compressor after the introducing the fluid. The fluid was murky when it came out and I saw little or no debris of any sort. The compressor showed melted plastic around the bearings, so I don't think anything had broken off inside it. Visual inspection of the old compressor looked clean on the inside.

I took it to an independent shop that put in the 2.67 lbs (per the sticker on the frame) into the high side. Not sure if high side was the way to go. . . but I had little input into telling the mechanics how to do it.

I am considering bleeding off some and seeing what happens.

Thanks for everyone's input.
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Myron
Houston
02 540i (working my way back up)

Past rides . . .
99 528i (got it back)
89 325i (now I'm legit)
99 528i (now I look like an adult)
02 M3 (dream car reality-er)
97 M3 (dream car reality)
97 328i (Now it's Bimmers for life)
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Myron '89 325i



Joined: 02 May 2007
Posts: 34
Location: Houston, TX

PostPosted: Mon Sep 17, 2007 5:14 pm    Post subject: Reply with quote

Took it back to the shop and had them recover about .3 lbs of freon. The pressure stabilized and I now have cold air.

Thanks for everyone's help!

If anyone needs tips on how to replace their expansion valve on an E39 without tearing apart the dash, let me know. (take some Yoga classes a couple of weeks before attempting! Wink )
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Myron
Houston
02 540i (working my way back up)

Past rides . . .
99 528i (got it back)
89 325i (now I'm legit)
99 528i (now I look like an adult)
02 M3 (dream car reality-er)
97 M3 (dream car reality)
97 328i (Now it's Bimmers for life)
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guyjabahbimmer



Joined: 17 May 2010
Posts: 1

PostPosted: Tue May 18, 2010 8:32 pm    Post subject: AC Expansion Valve Reply with quote

Please let me know where the ac expansion valve is. I took apart the glove box, found the FSU and looked everywhere for it. None of the plastic covers make sense, so I didn't start taking them off. The have torx screws and clips. Please any help would be greatly appreciated!
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Myron '89 325i



Joined: 02 May 2007
Posts: 34
Location: Houston, TX

PostPosted: Sun May 30, 2010 7:42 am    Post subject: Reply with quote

Getting to the expansion valve does not require removing the glove box.

You need to take off the left kick panel in the passenger foot well and the panel below the glove box.

Once that is off, there is a black plastic housing (looks shiny) that's shaped like square tubing running up into the back corner of the foot well.

Remove the screws to take a piece of that black cover off and you should see the aluminum tubing coming into the expansion valve.

Getting it out can be tricky, but if you have a socket wrench with an allen head adapter, you can get it in there.

Good luck.
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Myron
Houston
02 540i (working my way back up)

Past rides . . .
99 528i (got it back)
89 325i (now I'm legit)
99 528i (now I look like an adult)
02 M3 (dream car reality-er)
97 M3 (dream car reality)
97 328i (Now it's Bimmers for life)
Back to top
View user's profile Send private message
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