Bad evaporator. Bad news?
 

I have a 95 E320 and my mechanic told me the evaporator is leaking. He wants $1000 just for labor and he also told me he even prefer not to do it since it is a lot of work. Is there any quick fix for this problem?

Hmmm... Not sure I'd want to deal with a licking evap.

If the evap is leaking, on the other hand, this is a common problem in the W124 chassis which can only be remedied by replacing it. $1000 is not a bad price, since practically the whole interior of the cabin surrounding the dash and related parts must be removed. There is no way around this unfortunately.

I would not be inclined to have someone that told me what is quoted above do that job for me. His labor price does not seem unreasonable, it even seems low to me. Maybe he marks up the cost of parts quite a bit and make some money there.

It's a lot of work because the evaporator is BURIED in the bowels of the dash!!! Translation: the WHOLE dash has to be removed in order to access it.

I had it done at the dealer many moons ago for about $1800...I believe the evap goes for perhaps $900. Fortunately, the extended warranty covered it.

The original evaps were aluminum...these were prone to failure. The replacements are copper (which is what it SHOULD have been from the start).

Your mechanics price is REALLY a bargain! But I don't blame him for not wanting to do the job!

This is not a true statement regarding the material selection. I have had many, many flawlessly operating (long term) evaporators made out of aluminum. Aluminum when properly passivated is more corrosion resistant than copper, while maintaining high heat transfer capability.

The problem is thus elsewhere, either in the design of the evaporator core, or in its manufacture.

Also, an evaporator core should only cost around $350 or so max, not $900.

As for the work. Yes, removing a vehicle dashboard is a ton of work, moreso on the Benz. I would take the opportunity to replace the heater core as well and check all of the other climate control components.

If it were me, and someday it will be, I'd take this project on myself, except for recovering the refrigerant. I can flush, vacuum and recharge, but I don't have an approved recovery apparatus.

The other thing to consider is this: Every time, for whatever reason, if I have to crack open an A/C system I always 1) replace the dryer, 2) remove inspect and flush the expansion valve, condensor and line set and 3) replace ALL o-rings and seals. I also consider removing the compressor to drain the old oil, flush, inspect and refill with new oil. Doing all of this has led me to many trouble free miles on every A/C system in my family's vehicles with no other issues out of the eight systems I've worked on so far. I did have trouble with a blown compressor on one car that I converted from R-12 to R-134A after two and a half years, and so I replaced the condensor, compressor, dryer, expansion valve and converted it back to R-12 and it hasn't had any problems in the last five years.

32 years experience turning wrenches, mechanical engineer, and more importantly a certified A/C tech...

Good luck either way you go with it.

See posts #5 & 7 in the thread in link below for what I change when doing this job. Mechanics who are experienced love these jobs because they pay so well. I have a friend who owns an MB shop and and one of his guys has done over 100 of these jobs. He can do the entire job, on a 124, in 8 hours.

http://www.peachparts.com/shopforum/showthread.php?t=152840&highlight=evaporator

Strider, as you said, the problem may not be the aluminum, per se, but something like the junction points of the assembly. The problem could be thermal cycling fatigue of dissimilar metals or poor braze joints. Aluminum is more difficult to braze than brass and copper.

Should my evaporator ever take a dive, I'll be sure to bring it in the lab and do a thorough analysis to the root cause of failure and put an end to any speculation.

Pound-for-pound, copper and brass have better thermal transfer characteristics than aluminum. The copper organization makes a point of this. It allows designers to use less space for the same thermal transfer requirements.

Sorry...that was a quote I got for replacing a Jaguar evap...got my wires crossed there. :silly:

I'm probably wrong about the aluminum too...it's just that we had a house unit with an aluminum evaporator that also went south prematurely...so I'm not fond of aluminum units for that purpose...