My turn for the Evaporator Party

[brewtoo]

1990 124 300E. AC won't hold a charge. Significant leak.

I've been told that the definitive confirmation for the leaking evaporator is to remove the blower motor and look at the evaporator. I did. The photos are below. You can see that one side is nasty and oily with lots of crud stuck to it. The other side is clean. Does anyone agree or disagree that this evaporator is leaking?

Of course, MBUSA told me awhile back that they never heard of a leaking evaporator in one of their cars so if mine is indeed leaking, it will, I guess, be the first one ever to leak. Just like the upper neck on my radiator was the very first one that ever broke off.

Everything is starting to look so old in there, I wonder if I should even do this job. It's the challenge I suppose. And there's no car payment. That's nice. The car still runs great and the general public doesn't even know it's 17 years old. I think these 124s still look good. And of course, it would cost as much to have this done as the car is worth. Probably more. OK, I've had this car a long time and I still love it.

So, a couple of questions before I start the Big Project. Should I just leave the blower motor out and proceed, or put the blower motor and wiper motor and all those parts back together first, before I forget how they go together? Any advantage to having the blower motor out already?

Is it better to remove the front seats or leave them in place?

Is it better to leave the car flat on the ground or to drive it up on ramps in the front to elevate the work area a bit?

Any other comments or suggestions? Did anyone ever do a complete DIY on this job?

Which evaporator is best for a replacement?

What questions have I forgotten to ask?

Thanks

If it isn't leaking now, it will. I assume you did this effort as a result of insufficient cooling or none at all.

Replace with an ACM evap that has the expansion valve attached.

Replace receiver drier and make sure your pressure switch on the drier is the red one or you need to replace that at the same time. I have an extra on if you wish to purchase.

My water hoses were a bit difficult to disconnect, but I removed battery to get better access and got it. I ended up taking the battery tray out and cleaning and repainting. Ever read the book "If you give a pig a pancake"

Order a oring kit for your heater core and replace the o-rings as an extra preventive maintenance.

Yes take the fan out to help you remove the box.

Leave the seats in place.

Replace all the vacuum pods while you have the dash out.

Get the printouts from the CD for all steps.

Take digital pictures of every screw you remove, because there are probably 6-7 different types.

There is a caution on removing the leg room flap arm so the plastic piece is not broken.

Everything is just like the book says, straight forward and no MB tools or MB 40 hr training required.

Inspect the shifter bushings when you disconnect the speedo from the tranny.

Put a few drops of ATF on the fan motor bearings while it is out.

Replace cabin air filters.

Use a pry bar like a Super bar to release the box from the firewall

You will need to replace the weatherstripping around the evap box. Cannot get this from MB. I went to Lowes. I think I used 3/4" wide and maybe 1/2" thick. I would not use plumbers putty as the sealer as it is not intended for plastic and non-stainless parts (unless you find a less acidic type). I used silicone based caulk - little messy if you aren't careful.

I never found the plug for the center vent dial light, so I cut the wire and reattached.

There are a lot of plugs to disconnect, so make sure you reconnect them all. I had forgotten the cigarette lighter and I had to remove the console again to find it.

I am sure I left something out, but plan well and take your time.

PS I have just completed mine and I think I might have damaged my ignition switch as a result of not removing it per the instructions. See my post on my fan acting irratic.

94 E320 ACC Fan Irratic After Evaporator Replacement

Olin

[Bruno_300TE]

Hi
I did mine about three months ago. Olin made very good comments already. The job is not that difficult, but time consuming (22 hours). BTW, everyone will be impressed after you show them a pic with everything disassembled. The car is better left on the ground. I'd leave the front seat in. But removing the steering wheel helps. This is also what the manual recommends. I took pictures from the vacuum lines and how they are connected. I screwed the fasteners back to their place where possible or attached them with tape. Be careful when disassembling the heater box, there are some clips and plastic that can break.
Good luck, Bruno

[J.HIDALGO]

The only thing I have to add is: use zip-lock bags to label and separate your bolts and smalls parts I would check the compressor and old the AC lines since if the evaporator goes, the compressor is not far behind (do a search on black death). I did not remove the steering wheel, I just extended it as far out as it would go...same thing with the seats, bring them as far back as they would go...

[brewtoo]

I've found this procedure to be like dealing with a hundred little jigsaw puzzles. As I go along, I am always impressed with the engineering expertise that went into this car. Like a fine watch.

Anyway, this little puzzle I have not figured out yet: See the piece of ductwork in the photo with the yellow "X" on it? After you remove the one screw in the floor, how do you get that out?

Just curious, has anyone experienced a failure of their replacement evaporator?

Thanks

[david s poole]

carefully,you have to make old brittle plastic give just enough to get it out. going back is the fun part.

[brewtoo]

OK, I figured out that to remove the ductwork above, you have to first remove the piece below that goes under the seats. No easy task. The plastic was not brittle at all, though, even after 17 years.

My toughest puzzle so far...the dash would NOT come out. Why? It seems that the guy who replaced my windshield a while back glued parts of the dash in for me. No extra charge.

I did not remove the steering wheel. I was going to but couldn't get the bolt loose. I figured I'd come back to it later but it turned out that it was no problem. I did remove the ignition switch.

I used a bit of compressed air to blow out the heater core so I wouldn't spill coolant in the car.

I've ordered ACM evap w/expansion valve and all new pods and a dryer and pressure switches.

I haven't broken anything. The drain hoses are one thing that deteriorated over time and have to be replaced.

It sure feels like I've gotten up close and personal with this car!

[J.HIDALGO]

You can get something better. I replaced them with plastic/rubber hoses from the plumbing department at Home Depot. it will outlast the car for sure...

[brewtoo]

I found the following interesting post on one of the newsgroups....Perhaps blaming it on mites is easier than admitting copper does not play well with aluminum. Our maybe mites really do eat Mercedes-Benz evaporators. Who am I to say?

I've seen and replaced the evaporator core on countless 140 body Mercedes.
It is a problem that Mercedes-Benz is aware of and has released an
"unofficial" explanation for: the Southeastern US has a particular variety
of mites that apparently "eats" and "digests" the bare aluminum. The result
is a hole that develops in the evaporator core and allows the R134A
(refrigerant) to leak. The new parts that are being installed are "mite
resistant" - no kidding. The parts are dipped in plastic and coated with
chemicals. By the way, the 124 body Mercedes has had this problem for
years. I have heard some new Mercedes have actually lost the refrigerant on
the new car lot before it was sold. If your car is out of warranty there is
no alternative for repair payment. If you have an extended warranty, that
company should pick up the expense. If you have any other questions check
us out at www.peachparts.com.

Benzmac

[brewtoo]

As my wife says, I have completed my Journey to the Center of the Earth.

The evaporator pics are below.

Obviously leaking on the left side. Tough to tell exactly where, though. I expected to find the leak at one of the copper/aluminum joints but I don't believe that is the case. Looks like the leak is probably out in one of the tubes near the top.

There's less copper in the evap than I expected. Only the parts in the pics. The other end was completely aluminum. Maybe it was mites after all!

I have the MB Climate Control service book. While it does give procedures to replace the heater core and is quite thorough with all the AC items, there is no mention of replacing the evaporator. The heater core can be replaced with the box in the car but replacing the evaporator is a really huge job because it is absolutely buried. It really does seem like MB never expected these evaporators to be a problem. Surprise, surprise!

[brewtoo]

New parts arrived today. ACM evaporator with expansion valve installed.

Problem is, one of the tubes was bent in shipping. I know the tubing these are made of is thick and the passageway is small. I'm concerned about an obstruction here. This one might be closed entirely. In the pic below, what do you think? I'll have to wait another week to get a new one but I'm afraid this evap might freeze across the middle because of the obstruction. I do not want to do this job twice because of a faulty part.

Also, the expansion valve says R134A on it. Does that mean it will work with both R12 AND R134A, or ONLY R134A? Mine is an original R12 system and is going to stay that way.

Thanks!

[Ron in SC]

Problem is, one of the tubes was bent in shipping.

It's damaged you need a new one. I don't know who you're dealing with but they should be able to send a new one out right away and credit you for the old one when they get it back.

Do you think that dent happen when it was made? That's kind of what it looks like. Was the packing material damaged in the area of the dent?

I think that expansion valve will also work for R12.

[myarmar]

EPC lists two different expansion valves for 1990 W124:
201 830 06 84 for R12 only
140 830 04 84 for R134 only

[david s poole]

the 134a valve works fine with r12 you will not notice any diff.i would not install that evap make them replace it.btw i looked at the pics of the old evap and can see where the epoxy dissappeared where the copper fits into the aluminum.benz did not know that long term the 134a would compromise the epoxy[neither did anyone else]but they knew that aluminum would transfer heat much better than copper and was half the weight.

[brewtoo]

The new ACM core came in a sealed box that looks like it was probably a factory box with an official-looking ACM label. Unfortunately, they just put it in the box, the fit was very loose and the core was able to bang around inside the box. There was virtually no packing material in the box...only one piece of thin cardboard that wrapped around the core. Damage was almost inevitable.

Meanwhile, the much less delicate and much less expensive dryer came in a specially-made box that held it place very, very securely.

Regarding the 134A eating the epoxy, mine has always been an R12 system. Wonder what went wrong?