racepar1

I've been a mechanic as a profession for over 10 years. I'm MACS certified and I'm an ASE master tech. I have never even once drained the compressor oil to service the system, nor have I ever been instructed to do so. New oil will have little/no effect on the performance of the system. It's simply a lubricant, the system does not get hot enough to break it down. Changing the oil would only remove a small amount of contaminants, since there is still oil coating every surface in the system, and if the system is working properly it shouldn't have hardly and foreign particles in it to begin with. It is definitely NOT the worst idea in the world to change the oil. It is just not necessary and will not have any measureable affect on performance.

As far as how much oil is in the system, the compressor alone usually takes 6-8 oz. The reciever/drier, condensor, and evaporator each hold another ounce or two.

Mikester

^^Dude, not doubting your credentials or meaning to argue one bit... However I will say that when I purged the old oil out of my system, there were disgusting black goopy chunks of god-knows-what coming out of the lines...

With the lines cleaned/purged, new filter drier & fresh oil & charge, the system not only functioned better (more efficiently than a gooped up 20yr old AC system), but the air smelled cleaner and it became so cold I had to roll the wondows down to warm up. Whether or not it's 'required' under ASE or not, experience has told me that the difference is more than significant.

__________________

racepar1

The functioning of the A/C system has absolutely nothing to do with the way that air smells. That was a complete coincidence. The scent of the air is all in the duct work and the crap that collects on the evaporator. You wanna see some NASTY shit, pull out your evaporator and clean it. since 240's don't have cabin air filters all kinds of nasty crap gets in there. On top of that, since the evaporator gets cold enough to condense the moisture in the air, all the nasty in there gets all wet as well. I'm not saying that your A/C didn't work better after servicing, of course it did. I'm just saying that changing the compressor oil was not what made the difference. If your particular system was full of crap then flushing it out would definitely have helped some. In most cases though the system simply isn't that full of crap.

I'm also not saying it is a bad idea to change the compressor oil, I'm just saying it's not necessary. Granted, most compressors don't last 20 years so most of the time the oil would have been new by then. It's standard procedure to flush the system when you replace the compressor as well so most times they system would already have been flushed too.

I only mentioned my credentials and experience to emphasize the fact that I do know what I'm talking about and not just spouting crap and heresay. I'm not arguing as much as correcting some minor mis-information and bringing a qualified viewpoint into the thread. You're not necessarily giving bad advice, some things are just not quite technically correct.

Mikester

^^His system was full of crap- he said in his first or second post that he put stop leak in it... wouldn't be surprised if the knucklehead PO of mine did the same judging by what came out.

Again, I'm not a trained mechanic, but IMHO, stop leak is a great temporary solution' but when it comes to taking the car down for maintenance & correcting the issue, it needs to be purged the hell out of the system to the max extent possible. That's why I told him that he needed to completely purge, clean and reservice his system from scratch.

__________________

racepar1

I would NEVER put stop leak in ANYTHING. All it does is complicate the actual repair in the end and a lot of times can end up damaging other components. I say fix it right the FIRST time!!!

If there was stop leak in it then yes, it definitely needed to be flushed. I came in halfway through the thread so I missed that part.

Flushing the system is a lot more involved than simply draining whatever oil you can get out though. It requires a special cleaner and a special apparatus to apply the flush. It is basically a cylinder with a hose with a nozzle coming off the bottom and a schraeder valve on the top. You fill the cylinder about halfway with the cleaner and then charge it with air. Hold it tightly to whatever component you're flushing and pull the trigger. I think they DO sell DIY flush kits as well, but since I have the actual equipment at my disposal I have never bought one. Never, EVER flush the compressor like that though. That you just drain as much as possible and re-fill.