questions about bad AC /evaporator
 

After reading Ashman's post about his leaking evaporator/dying AC, I got a little concern. It seems that I may have a leaking evaporator because I noticed the same symptoms that Ashman described. Although I only found a few drops of greenish oil near the tranny and the leak has never reoccured (I have checked under the car occassionally and no longer see any leaks since first discovering it), the AC no longer blows cold air. Well, I'm not too concerned about having no AC--I can live with that for now. My concern seems to be about adding oil to the evaporator or something like that so that the compressor won't wear itself out. (Someone said this in reply to Ashman's post.) What does that mean? First, I don't even know where to add the "green oil." I don't plan to use my AC, so is adding oil necessary? Does NOT OPERATING the AC mean there will be no moving parts in the AC unit, and therefore no oil consumption? I don't plan to fix my AC unit/evaporator or add freon anytime soon. Is operating my car (90 190E) with a leaking evaporator or a faulty AC bad for the engine? I know these are paranoid questions, but I just need to know that everything is alright. Thanks.

Oil is probably the hardest thing to deal with on a leaker. The amount of oil in the systems vary but are in the range of 6 - 10oz. The amount in a system at any specific time can only be determined in one way: drain and flush and reoil to spec.

In practice oil is considered to be distributed fairly evenly through the system. Recommendations are for adding an oz. when replacing a drier. Maybe two oz. for evaporators or condensers, etc. If the car is having its first leak one to two oz. might be added determined by the type of leak - early Turbodiesels had a low side hose that was the lowest part of the system. The hose often leaked and when it did it leaked mainly oil as the oil lay in the area the leak existed in.

Which oil is in the system is also a major issue. The green mentioned is the flourescent dye that was added to show in a black light. When its visable in white light the leak is very large.

The amount of oil in the system is not a factor if the system is not in use. Keeping pressure in a non-used system is the most important factor. If pressure is gone moisture will enter. Moisture is the worst enemy of refrigeration componets.