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2001 E320
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Discussion Starter #1
2001 E320. I am in the process of replacing a bad ac compressor. I installed new expansion valve and dryer. I got what was supposed to be a "new" compressor from Japanese manufacturer. Installed it but then I could not get the system to hold a vacuum. Checked all connections and could not find a leak. Put clean compressed air into low side input port under about 20-30 psi. I could hear the air leaking from the compressor. Removed the compressor and repeated this test on the bench. Air coming out of around the front shaft. This is when I put about 20-30 psi on the low side port with the high side port plugged.

To me this indicates a bad compressor, correct?

I got the supplier to send me another compressor, this time a re-man. Before I went to the trouble to install I repeated the bench pressure test. This new compressor also leaks air around the front shaft seal.

So now I am doubting myself in saying this leak means a bad compressor. I can’t see how they could work when the ac system has to hold pressure.

I believe both of these compressors are bad, correct? Just looking for confirmation that these are bad and I am not doing something stupid.

If so I will return and find another supplier.

Thanks.
 

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1996 210.020
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3,972 Posts
Welcome to the forum, Woowoo.

It sounds like the compressor is bad. There should be no leaks at the shaft seal. It has to hold a vacuum and considerable pressure.

You also need another new dryer at this point. Use an old one for the first pressure check (or vacuum check if it's all you have), and if it holds, swap the new one in with new seals. Checking pressure with nitrogen prevents damage to the dryer, or water absorption by the oil (you hope that the dryer gets the water before the oil does).

I don't know if the rebuilt Denso compressors are reliable; probably so if you get a good builder. It is also possible to change just the shaft seal on most compressors, and I presume that our Densos are like this. Not that you want to go this route.
 

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2001 E320
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Discussion Starter #3
Hi Matt,
Thanks. It just seemed weird to get 2 bad compressors in a row. I have my drier sealed off and when I did the original pressure check this was on the low pressure side and the air was coming out through the compressor shaft so not a lot of pressure was created in the system.The system was totally empty at this point so do you really think I ruined the new dryer? They are easy to change I just hate doing it and spending the $ if its not needed.
Thanks again.
 

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1999 E55, 2001 E320, 1990 560 SEC, 2004 ML350, 2001 ML55, 1995 S500, 1998 SL500, 2010 E550 Sport zoo
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7,035 Posts
Are you trying to fire the system up on air pressure alone, without refridgerant and without oil ? I would not recommend that, since that can prove to pound a good system to pieces early.

There are (3 Levels of compressors available:

"Rreman" there are many different quality levels of reman: from no-name independents, Cardone, and up to classier pro guys who make shop quality rebuilt units. The quality of the reman can be from schlock to very good, the appearance of the compressor is the gerneral tip off.

There are "new" knockoff of the Denso unit available, made in Chian or Indonesia. They look new, though not quite as good long term as the original Denso. I personally have note aJapanese mde knockof, but nme can b confusing.

Tehn there is the original brand new Denso unit, same as what you would buy new from the dealer.

Rough Cost prices: Reman from $250-$325. Knock-off new Non-Denso $350-$395. New densor $500.

If you were using original drier and expansion valuve, ditch that for new. If you used new, if you did not use refridgerant the drier is still OK, but in doubt replace.

Good Luck !
 
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