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  #1  
Old 06-10-2000, 03:42 PM
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Join Date: Apr 2000
Location: Falls Church, VA
Posts: 5,316
With a the compressor siezed, I thought I would use vaccuum to test for evaporator leakage. I removed the expansion valve, connected my trusty vaccuum pump and got 10 inches of vacuum, which it gradually lost in about 2 hours. The pump and tubing that I used held 10 inches all night (wish I could do that!).

I realize that the system works on pressure not vaccuum. Is this a valid test for leakage????

Removal of the expansion valve revealed copper fittings, so I am assuming that the evaporator has been replaced. From the posts, I assumed that a copper evaporator would be bullet-proof. Comments???

Thanks.

------------------
Chuck Taylor
Falls Church VA
'86 300E 5 speed
'95 C220 (wife's car)
'98 Porsche Boxster
Past: '79 280E, '82 300D (18 yrs), '77 240D,
4 250C's
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  #2  
Old 06-10-2000, 04:35 PM
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Join Date: Jan 2000
Location: New Bedford, MA USA
Posts: 1,583
Chuck, how did you make the attachments to the evap core? When usin vacuum to check for leaks, the connections are the most important part of the test. Gotta be air and vac tight. I am assuming that the compressor is out of the car, otherwise you should check the entire system when connected. My local A/C Guru told me the system should hold 20 inches for an hour. But, he also likes to pressure test systems with stubborn leaks. He will pump them up with filtered, dessicated compressed air to about 150 PSI and watch for loss of pressure. I doubt this is a standard way of chasing leaks, but he says it works for him. Puts soapy solution on suspected area of leak and looks for bubbles. Says it's cheaper that using up R12 to find leaks.
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  #3  
Old 06-10-2000, 07:41 PM
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Join Date: Apr 2000
Location: Falls Church, VA
Posts: 5,316
Jeff -

Thanks for the quick response.

Great minds (may)think alike. I re-tested with better connections and it held without problem for two hours.

So I am much relieved that the evaporator seems OK. I am now working my way back through the system trying to find out where the R12 went. Will tackle the manifold pipe next. Am working in 14 years of grease and dirt. Stay tuned.

------------------
Chuck Taylor
Falls Church VA
'86 300E 5 speed
'95 C220 (wife's car)
'98 Porsche Boxster
Past: '79 280E, '82 300D (18 yrs), '77 240D,
4 250C's
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  #4  
Old 06-10-2000, 10:31 PM
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Join Date: Mar 1999
Location: Suwanee, GA, USA
Posts: 4,712
Some of the aluminum cores had copper fitted pipes. The soldered them together and they leaked like crazy. All Mercedes cores are made of aluminum because of its great heat transfer rate.

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Benzmac:
Donnie Drummonds
1992 500E (very soon I hope
1981 280GE SWB
ASE CERTIFIED MASTER AUTO TECHNICIAN
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MERCEDES SPECIALIST 8 YRS
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