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'85 325e A/C Rebuild Update

 
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jamesnau



Joined: 19 Jul 2002
Posts: 520
Location: NC State University

PostPosted: Sat Jul 14, 2012 5:23 pm    Post subject: '85 325e A/C Rebuild Update Reply with quote

UBBers,

I removed the entire system (except for the evaporator), flushed everything (Enis, I followed your lead on flushing the evaporator), had the suction and discharge hoses repaired (rubber portions replaced), and got it all back together last Tuesday night. Then pulled a vacuum....wouldn't hold.

Today, I intended to methodically search for leaks. But after replacing the valve cores, I decided to pressurize the system with air to see what would happen. I ran it up to 70 psi, and it held rock steady for 2 hours. So, there are apparently no leaks (under pressure). Then pulled another vacuum...lost it completely within minutes.

My research indicates a bad compressor shaft seal. It holds pressure, but not vacuum. I have an email into Griffiths, who supplied the reman compressor. I hope they stand behind their product...it was $400. I will replace the receiver/drier again since I probably saturated it with the compressed air I put in the system. I am surprised how inexpensive the r/d is...less than $20 from Pelican.

So, there we are. I am looking for another source for a compressor, and can't seem to find one. If any of you have suggestions, please let me know. My compressor is the old style Behr with round ears (not square pads) and without the temperature switch on the body of the compressor.

I guess I should be upset, but I really am not with a "new" e36 in the garage...a 1995 325iC with only 69,000 miles...I paid $7000 for it. Hard to believe.

Jim
'85 325e, 215K miles, born October 1984, original owner
'95 325iC, 69K miles, born September 1994, second owner
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85-325e



Joined: 30 Jun 2002
Posts: 4712
Location: Southampton, NY

PostPosted: Sat Jul 14, 2012 8:53 pm    Post subject: Reply with quote

Jim... Sorry to hear you have this problem. Are you absolutely positive everything's tight? Is it possible that an o-ring is out of whack, although I will admit that they're fairly straightforward.

I guess if it held pressure, the system's closed. But you have to wonder what's closing when pressurized and expanded, but what's opening when shrunken and vacuumed.

Hopefully Griffiths will be able to help.

What rubber portions are you referring to Jim? I don't remember a single rubber component in the system other than the o-rings...
_________________
Cosmo - 1985 BMW 325e, Single Owner, 265,000+ ORIGINAL miles and still going strong! But now on the East Coast and the salt air corrosion is eating my beautiful car alive... Sad

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jamesnau



Joined: 19 Jul 2002
Posts: 520
Location: NC State University

PostPosted: Sun Jul 15, 2012 8:09 am    Post subject: Reply with quote

Thank you, Enis.

I was so surprised with the results of the test I conducted yesterday. I started by replacing the valve cores because I thought the valve down on the compressor intake manifold was leaking. My gauges didn't budge one bit when I pressurized the system with 70 psi air. Held rock steady for two full hours, so I thought the valve core was the problem.

I then pulled another vacuum. Ran the pump for a full hour. Vacuum was lost in a matter of just a few minutes after closing the hand valves and shutting off the pump.

I came inside and googled the problem, and several forums came up in which people reported this problem. If the compressor shaft seal is similar to a typical oil seal, the lips are angled a bit. Pressure tends to force them more towards the shaft, creating a tighter seal, while vacuum tends to pull them away creating a leak. One of the people who responded told a funny story about Houdini--How can he escape so easily from inside a locked bank safe? His punch line--safes are designed to keep people out, not in. Apparently the same goes for ac compressor shaft seals. It could be the seal was nicked when installed, if Griffiths installed a new one to begin with. I flushed the compressor twice with oil before I installed it, and I was surprised to see how much crud came out. I am beginning to think the compressor was used, not rebuilt.

Yes, both the suction and discharge hoses have rubber portions--have to be this way to allow for engine vibrations and the resulting compressor movement. These hoses had deteriorated somewhat due to engine heat. On my car, the suction hose is very close to the exhaust manifold. There is only one entirely metal ac line, the liquid line from the r/d to the firewall. The other 5 lines have rubber sections.

Will keep the UBB posted,
Jim
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DJB



Joined: 19 Jan 2007
Posts: 293

PostPosted: Thu Aug 16, 2012 6:39 pm    Post subject: Reply with quote

It's a late reply, but perhaps still useful.

The A/C compressor uses a carbon face seal. The rotating seal is formed by a graphite-carbon disk pressing against a polished steel disk. The inner disk rotates with the compressor shaft. It is spring loaded, and uses an o-ring to seal to the shaft, but the o-ring joint moves only to compensate for wear. The outer disk is stationary, sealed to the case with an o-ring, and held in place by a circlip.

The spring provides some of the sealing pressure, but most is provided by the gas pressure. The spring only need to be strong enough to keep the sealing surfaces together when you pull a vacuum.

It's a little surprising that a rebuild compressor would have a too-weak spring, or a face seal leak. They should have done a vacuum test after re-sealing the compressor.
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jamesnau



Joined: 19 Jul 2002
Posts: 520
Location: NC State University

PostPosted: Thu Aug 16, 2012 7:49 pm    Post subject: Reply with quote

Thank you, DJB.

I think I recall coming across your posts on other bulletin boards. People think very highly of your auto ac expertise.

Thank you for your explanation of the seal. It was hard for me to believe the performance of the first supposedly reman compressor. I am not exaggerating when I say the complete vacuum was lost in a matter of just several minutes, yet pressure held rock steady for 2 (or more) hours.

Griffiths came through and credited my credit card for the entire cost of the compressor plus shipping. It has been just over 2 weeks now, and my wife is still very happy with the ac performance.

Say, I do have one final question...what is your recommendation for a heat shield for the suction line? It is so close to the exhaust manifold, and I am not happy with the material currently used to protect the line.

Thank you in advance,
Jim
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Soviet Sniper



Joined: 09 Nov 2004
Posts: 1081
Location: Edina MN

PostPosted: Thu Aug 16, 2012 10:09 pm    Post subject: Reply with quote

jamesnau wrote:
I do have one final question...what is your recommendation for a heat shield for the suction line? It is so close to the exhaust manifold, and I am not happy with the material currently used to protect the line.


I am also curious. I put some foil+foam pipe insulation tape on mine, have yet to see how well it performs. Confused
_________________

1988 325is | 199k+ | First car (now s52 powered) Cool
1992 Saab c900 | 200k+ | Winter vehicle
1982 Virago xv920j | 25k+ | Cool
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