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#1
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W126 1991 560SEL A/C leak
On my 1991 560SEL, I have a very frustrating leak in the a/c system. The car would hold pressure to 75psi on the high side. The rest gets leaked out. I replaced the condenser, low side hose and compressor.
I pulled a vac and it held, then I charged the system and used my sniffer to check for leaks. Nothing showed up at the condenser, lines or compressor, so I stuck it through the vents and up by the gas pedal where the expansion valve is supposed to be. Still no leak detected. I've recently replaced the compressor and the condenser on this car in an effort to cure this problem. Any thoughts as to where this leak could be would be gratefully appreciated. It's going to get hot in Texas over the next couple of months.
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With best regards Al |
#2
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Check the evaporator behind dash, put dye in it then check ac drains under car to see if dye traces are present , its very common for evaporator to leak.
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#3
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What are your pressures when the system is full? With this scenario I'd be suspicious that the fans aren't up to snuff causing high side pressure spikes. In which case it would only leak during pressure spikes and be very hard to detect. Flourescent dye is essential for finding difficult leaks.
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90 300TE 4-M Turbo 103, T3/T04E 50 trim T04B cover .60 AR Stage 3 turbine .63 AR A2W I/C, 40 LB/HR MS2E, 60-2 Direct Coil Control 3" Exh, AEM W/B O2 Underdrive Alt. and P/S Pulleys, Vented Rear Discs, .034 Booster. 3.07 diffs 1st Gear Start 90 300CE 104.980 Milled & ported head, 10.3:1 compression 197° intake cam w/20° advancer Tuned CIS ECU 4° ignition advance PCS TCM2000, built 722.6 600W networked suction fan Sportline sway bars V8 rear subframe, Quaife ATB 3.06 diff |
#4
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Thanks for responding, I only measure the pressure when I charge the system and at that point I charge to no more then 225psi on the high side. I will check the fans.
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With best regards Al |
#5
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Did you reseal the expansion valve? It is a BIG PITA so most cars never have it done. My SDL slowly leaks from there and my 300SEL used to also.
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I'm not a doctor, but I'll have a look. '85 300SD 245k '87 300SDL 251k '90 300SEL 326k Six others from BMW, GM, and Ford. Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG] |
#6
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Eric,
I haven't touched the expansion valve, my buddy David Poole seems to think it would be there and the sniffer may not pick it up because it's covered with some sort of insulation. It looks like a job for trained limbo dancers.
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With best regards Al |
#7
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Quote:
It was the biggest pita job I ever did.
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Eugene 10 E63 AMG 93 300te 4matic 07 BMW X3 14 Ford F-150 Fx2 |
#8
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I recently discovered one of the nuts on the line from the receiver to the condensor was bad. It literally broke in half when I touched it so it was obviously the source of my leak. This is the line that's right next to the air intake to the right of the radiator.
I didn't notice this until I was swapping out my US headlights for Euros. It's in a hard to see spot otherwise. Worth a look. I too was stumped about my AC until I saw this. |
#9
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The late 126s are a REAL bear due to that extra crash bar/dash support RIGHT in the way. I mean, RIGHT in the way. I just do not trust 20 year old o-rings.
The dealer even diagnosed my 300SEL as 'bad evap core' to the PO before I purchased it... all that was the matter were bad o-rings. I would agree with David. I have a slow leak on my low side schrader valve so I am going to visit him pretty soon. I do not have time to hunt down a recovery machine plus it is summer so everyone is going to want $$$$$$$ for them. Not to mention it is silly wasting R12.
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I'm not a doctor, but I'll have a look. '85 300SD 245k '87 300SDL 251k '90 300SEL 326k Six others from BMW, GM, and Ford. Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG] |
#10
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On my 560 it was the expansion valve...
I did a writeup on replacing the valve. You can find it at this link:
http://www.funnyyouasked.com/Mercedes/W126/ExpValve/removal_and_replacement_of_expan.htm The part is not very expensive. It is imporant that you know how to empty and refill the system, which (by your post) I suspect you know. Figure about an afternoon. Good luck!
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Henry Bofinger 1989 560 SEL (black/black) 2001 Audi TT Roadster (silver/grey) |
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