Does anyone have experience changing the A/C evaporator in a '90-'93 W124? If so, please share any helpful hints and/or nightmares.

Just print out all the sections of the FSM that apply and work through it. It will be about a 15 or 16 hour job. It's not difficult as long as you have the manual pages at hand, just time consuming.

Replace ALL pods while the dash is apart.

Are you SURE that the evap is your problem? You won't want to do this job unless you are 100% SURE!

__________________
2001 SLK 320 six speed manual
2014 Porsche Cayenne six speed manual

Annoy a Liberal, Read the Constitution

Yes, I'm absolutely certain. There are no leaks anywhere else in the system, and the system works when freshly charged, but only for a few days. Please elaborate on pods. I'm not familiar with them and their issues.

its a long job - Ive tackled it for a freinds E320, for confirmation we had it sniffed too, and the sniffer was beeping at the vents.

The A/C technician (at a toyota dealership) knew of the issues of evaps in late W124 cars, he knew of an owner who opened up the entire dash to replace the evap and the leak was actually in the expansion valve H block, which could be replaced from outside the car in less than half hour. So best check it thoroughly.

__________________
2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)

Okay. And what about the vacuum pods? What experiences have you had (or heard of people having) with those? In other words, why should I be changing them and how many are there?

Some of the vacuum pods are easier to change with the dash off. So since the dash is off many say change those pods as insurance. I've found on my 123 I can change most of them with the dash still in place, but it is up to you.

I would verify with a sniffer or add UV dye and check the condensation dripping from the bottom of the car with the AC on to verify it is the evap before continuing.

__________________
2009 ML320 Bluetec
1985 300CD
1981 300TD

Past Mercedes
1979 300TD
1982 300TD
2000 E320 4Matic Wagon
1998 E430
1984 300SD
1980 300SD

I think a lot of people will believe it's a foregone conclusion that ALL w124 evaps WILL leak and that's the source of the A/C woes, when in fact there are plenty of other components that give up the goat early and are the true culprits. I was in my indy's shop a while back and looked at the carnage that was an evap replacement, he said it's at least 12hrs if you have done it before AND nothing breaks and/or gets stuck, but even with experience he said it's likely something will break and the dash will have some defects when reinstalling, so tread lightly.

Talked to one of the techs at our local MB dealer about it one time. He said that they won't even tackle a job like that because of the risk of so many old parts breaking and crumbling. Doesn't mean it can't be done....just means it's a job that one might end up regretting.

How long will it hold a charge for? It could be a candidate for Cryoseal, which is a high-end sealant. That's what I used on my 92 300D. Over six years now and still no evaporator leak.

__________________
14 E250 Bluetec "Sinclair", Palladium Silver on Black, 153k miles
06 E320 CDI "Rutherford", Black on Tan, 171k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver, 142k mi, wastegate conversion

19 Honda CR-V EX 61k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

I recharged it a few times last summer. The first time, it held a charge for 2 weeks. The last time, it held a charge for 2 days. I put a red dye in the system that is visible in natural light or with a black light. With the help of a friend that's been working on AC systems for about 20 years (first in cars, now residential and commercial) I checked all the places in the engine compartment that could potentially spring a leak. We didn't have a sniffer, but this leak is so bad that my friend is confident that the dye would be visible. Once I get the center console out, will I be able to shine a light on the evaporator to see the dye?

You could do like I said. Put a minimal charge in (just enough to get the compressor to spin). Then add dye and run the ac. If you do it on a humid day you should see condensation dripping from the bottom of the car. Put a UV light on it to check for dye leaking at the evaporator.

Or you could do 20 hours of work on a hunch that it is leaking at the evap and then possibly find out that the evap was fine.

__________________
2009 ML320 Bluetec
1985 300CD
1981 300TD

Past Mercedes
1979 300TD
1982 300TD
2000 E320 4Matic Wagon
1998 E430
1984 300SD
1980 300SD

Will do. Thank you all for your advice.

Yes, my '88 300E still has the factory evaporator, no leaks, making icicles. Several times, however, I have come close to condemning the evaporator as the OP has done, only to find that it is not the problem.

Given the magnitude of this job, it is worth doing some serious investigation before going through the job.

__________________
2001 SLK 320 six speed manual
2014 Porsche Cayenne six speed manual

Annoy a Liberal, Read the Constitution

I don't remember the exact count because I haven't done a podectomy in a long time, but there are about a half dozen vacuum diaphragm pods under the dash that have a finite lifespan. The only one that I believe to be replacable without pulling the dash is the one for defrost. You can get at it, barely, by pulling the glove box liner.

If you determine beyond a shadow of a doubt that the evaporator is your leak, don't even DREAM of doing the job without replacing the pods. One of them, the fresh air pod, if bad can render your a/c almost as useless as if the refrigeration portion were non operational.

How have you determined that the evap is leaking? Dye? Electronic Leak Detector? Make DARN sure it is your problem before attacking this project.

__________________
2001 SLK 320 six speed manual
2014 Porsche Cayenne six speed manual

Annoy a Liberal, Read the Constitution

Yes, this is one of the best methods for diagnosing an evap leak. The only thing I would add is that if you don't get to the condensation water with the UV light, raise the car and examine the condensation drain tube CLOSELY. It will have left a trace, but you will need a strong UV light and the yellow glasses to see it.

Best of luck

__________________
2001 SLK 320 six speed manual
2014 Porsche Cayenne six speed manual

Annoy a Liberal, Read the Constitution

Good point.

__________________
2009 ML320 Bluetec
1985 300CD
1981 300TD

Past Mercedes
1979 300TD
1982 300TD
2000 E320 4Matic Wagon
1998 E430
1984 300SD
1980 300SD