PeachParts Mercedes-Benz Forum - View Single Post

Squiggle Dog · #83 06-21-2018, 06:02 AM

The evaporator was badly corroded at the bottom from debris gathering up, so it needed replacing. A new one is $1,050.00 from Mercedes and used ones tend to have corrosion problems. Fortunately, Four Seasons makes one that supposedly fits (because it also fits the R/W107, and I'm sure that's the ONLY reason an aftermarket evaporator is available for the W116), part number 54131, and they sell for $100-$200. I got one for $68 and free shipping from Summit Racing, of all places.

The evaporator is constructed entirely of aluminum other than the steel side plates. Some pictures show copper tubes, but this is misleading. However, I've read that all-aluminum construction is better as dissimilar metal corrosion doesn't effect it. Apparently even evaporators for cooling of buildings and homes are now all-aluminum and are lasting longer. There are also six rows of tubes instead of five, so it should be more efficient than the original. Unfortunately, the pipes entering and leaving the evaporator weren't correctly aligned. Design flaw? Poor quality control? One-size-fits-all not what it seems?

I had to tweak them quite a bit before the evaporator would fit into the case--to the point of nearly kinking the small tubes and having to squish them back round with pliers. And then more before the case halves would fit together. It was disappointing. I'm glad I didn't inadvertently puncture a hole, as afterward I loosened one of the caps to check fitment of a flare fitting, and it made a loud hissing noise as air pressure escaped. I let it vent off for what seemed like a very long time. Finally, I untwisted the cap and heard a BANG so loud that it almost popped my ear drums and the cap shot off. They put these things under some serious air pressure to test them at the factory!

The evaporator needed foam in between it and the housing to prevent air from flowing around it rather than through it, where it is the most effective. But, this was challenging as the tubes were much tighter than the original. All I could think to do was cut some 1/8" thick resilient high temperature silicone foam (from McMaster-Carr) into 1/2" strips and wedge them into the left side where it's really tight, and then push in some 1/4" thick, 1" wide high temperature silicone foam next to it for a tight seal.

The right side of the evaporator got just a 1" wide strip of 1/4" foam. Oh, here's another fun fact about the Four Seasons evaporator--the mounting holes aren't just lacking threads, but they are also off by a lot. I had to drill new holes and install captive nuts. Then I had to cut off the upper corners of the mounting tabs because they stuck up too high and were sharp.

I put 1/4" foam on the bottom of the case and 1/8" foam on the top of the case. It was tricky to put in the evaporator, but it's in there snugly and shouldn't have any major air flow leakage around the sides of it. Yes, I am building a space shuttle. Big whoop! Wanna fight about it?