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  #1  
Old 08-13-2007, 01:35 PM
Freybird's Avatar
1995 E300D 124
 
Join Date: Jul 2006
Location: Central Maryland
Posts: 18
Red face W124 Evaporator replacement, before I dive in

87 300dt
I've done a good bit of troubleshooting on my A.C problem. I know the problem is not the Klima relay (thanks to this board). I thought the problem was the Klima at first and had replaced it. The compressor comes on when the appropriate Klima sockets are shorted.
I've discovered that the compressor will not come on if the system presure is too low. Thankfully, at the last recharge, they added some flourescent dye to the system.
So 11pm, dark garage, and with my Blacklight in hand, I went searching for a leak. I saw nothing in or around the center nor side vents, and nothing on the floor. Then, I opened the bonnet, and found the only glow coming from the indicator on the dryer.
Next, I decided to lift the car and inspect beneath. Bingo! I was sure that this pipe was the culprit!(see pic) So I take the car back to a shop where mechanic say's "this is NOT an A.C. part"! It was glowing brightly and sprayed the surrounding engine parts (especially the bottom of the alternator), but has nothing to do with the A.C. He mentioned that this is a tranny cooler line and the glow is comming from a water pump leak. I use the Mercedes clear coolant and mix it with 50% h2o.
I scratch my head and take his word that the problem is the evaporator, even though his searching with a black light showed no dye-leaks anywhere. Next evening I fill a cup with some of the Mercedes clear coolant and hold my Blacklight nearby, NO GLOW! hummmm!
So, before I rip the dash out, can anyone give some other suggestions or shed some light on this condition?
Thanks,
Freybird
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Last edited by Freybird; 08-14-2007 at 11:25 AM. Reason: Add critical info
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  #2  
Old 08-14-2007, 11:19 AM
Freybird's Avatar
1995 E300D 124
 
Join Date: Jul 2006
Location: Central Maryland
Posts: 18
I've heard $3000-$5000 repair cost for the evap replacement, can someone confirm?
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  #3  
Old 08-14-2007, 12:32 PM
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Join Date: Dec 2002
Location: Colleyville, Texas
Posts: 2,694
A couple of thoughts.

Dye will only be visible as it exits with some kind of medium. Water, oil or freon. As you have done, look for traces of dye. In the engine compartment, be aware of the fill point for the system. Trace the hoses from the compressor as they go through the engine compartment. Along the hoses you will see two fittings, one on each hose. This is where the dye has been ADDED so some may have "spilled" when being added. If it is around here, be suspicious of this being a leak.
The evaporator in the dash. Using dye, the only way you can determine a leak is to look below the car ( after it has been running for a while ) in the center of the car under the dash area. You will see the dye in the water that drains from the AC system. Looking in the vent does no good.

I would suggest spending or renting a AC freon "sniffer". The tool beeps when it senses freon. It's available for under $100. Once in your hands, trace the entire system in the engine compartment , slowly, for a "sniff" of freon. If nothing then make sure you get a confirming "beep" from the sniffer while sticking it in the vent ( center and side vent. stick it in as far is you can). If the vents give you a beep then its an evaporator problem and the dash has to come out. Think $$$$$.

When was the last time the system was recharged. A small, very small leak is sort of normal in a system. So if it's been 10-15 years since is has been serviced then the system could be low on freon. But it is an old car and a leak is probably the norm.

Spend the $$ to get the sniffer and test the system. Get a good confirming beep from the vents before removing or having the dash removed.

Dave
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Last edited by dmorrison; 08-14-2007 at 12:46 PM.
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  #4  
Old 08-14-2007, 12:36 PM
Gene
 
Join Date: Mar 2007
Location: Buffalo NY
Posts: 1,082
I jsut had my evap drains cleared and if the evap leaks it coems down the drains, which are jsut above the tranny. So there's your glo.

Evap is a HUGE PITA since you have to pull the dash apart. To pay someone shoptime for that kind of R&R is wickedly costly.
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  #5  
Old 08-15-2007, 10:51 AM
JimF's Avatar
'94 S500: only 793 sold!
 
Join Date: Mar 2001
Location: San Diego, CA
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Quote:
Originally Posted by Freybird View Post
87 300dt
I scratch my head and take his word that the problem is the evaporator, even though his searching with a black light showed no dye-leaks anywhere. Next evening I fill a cup with some of the Mercedes clear coolant and hold my Blacklight nearby, NO GLOW! hummmm!

So, before I rip the dash out, can anyone give some other suggestions or shed some light on this condition?
Thanks, Freybird
Also found UV-dye in the A/C drains pipes, so it confirmed that the evap was leaking. Same as WINGAS found.
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  #6  
Old 08-15-2007, 11:00 AM
E150GT's Avatar
I'm a chicken
 
Join Date: Sep 2006
Location: SAN ANTONIO, TEXAS
Posts: 1,148
Check the expansion valve to under the dash by the evap. I could not find my leak for the life of me and one day I was trying to chase a water leak problem on my carpet. I was pretty sure it was the evap drains, so I pulled all the carpet and my parts tray and found oil and dye all over the expansion valve. glad it wasnt the evaporator.
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