I have a slow leak presumably from the evaporator and have had to recharge my A/C every three or four months. I used to do this myself on my cars that ran "Freon". Can someone tell me where to find the port to recharge the refrigerant on my E420, and does anyone have an opinion on adding a can of SuperSeal Leak Stop to the system. Thanks!

The port is forward of the brake booster on the driver's side in the low-pressure line which is larger in diameter and may be partially covered in black foam insulation. Don't worry, you can't connect to the wrong port on a W210 - the high and low sides are different fittings. As for stop leak - DO NOT USE IT!

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08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280

Thanks for the info. As for the Super Seal, I had high hopes about this product. A couple of A/C shops I've spoken to said they are using it on most of the cars they repair as added insurance to make sure that anything that leaks will be sealed and their customers aren't back within a few weeks complaining that the shop replaced the wrong part, and to recondition seals and O-rings. Seemed like the real thing from what I've read. Oh well...http://news.thomasnet.com/fullstory/472941/rss

That stuff really does work, but that's not the point. It is indiscriminate when it works. Meaning if there are any contaminants or anything else in the system that can "activate" the sealer, it can plug up your expansion valve or form a coating inside your evap, condensor, or hose passages. I've read here on the forum of instances where things were gummed up on the inside necessitating total replacement when the system was opened up for service somewhere down the line.

As for O-ring conditioner, I think the very nature of that concept is gimmicky. Think about it - do you have to condition head gaskets or brake caliper piston seals or crank main seals? No - you just replace them when they fail. If you have ever removed an O-ring from an A/C fitting you will see that the thing gets "crammed" up in there pretty well, to the point that I'm not sure how "conditioner" could help one that has decided to break down. In my experience the problem tends to be that the o-ring gets deformed and loses elasticity from being crammed in there for many years and then begins to leak. Either that or the fitting is corroded (in northern climates), in which case just replacing the $0.35 o-ring or clean/replacing/rebuild the corroded hose.

In my estimation, the correct way to remedy leaks is to replace the part or (usually) the seal or o-ring that is leaking. Stop leak is just a band aid if you don't plan on owning the car for any length of time. Just have pity for the next owner...

__________________
08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280

Well I've already replaced the expansion valve, the compressor, and the receiver drier (twice), along with the blower motor regulator I replaced today. I now have a leak from the evaporator, and the lowest quote in the area is $2800 for the replacement from an indie. I only plan to keep the car for one year max and I might sell it in the next few months. If I went ahead and replaced the evaporator, I would have spent the total blue book value on replacing A/C components in the last 9 months.