A/C flush

[goldNSX]

I'm going to change the A/C compressor this year before it ends in a black death (1991/90k miles). It was originally a R12, then converted to R134a with the Honda kit. I don't like having different oils in the system as I've ordered a R134a-version of the compressor of the later model. So I'm going to flush the system with a special A/C solvent, dry it with nitrogen and change the receiver. All other components are planned to be flushed and o-rings replaced with R134a ones.

Could anybody confirm the following:

- the whole system contains 140 grams oil (esther).
- 80 grams are already in the new A/C compressor.
- so 60 grams have to be added after flushing, drying, evacuating and while charging the system with R134a.

I know it's the expensive route but I hate things done only partially. :wink:

Thanks in advance.

 

[NSX-Files]

Be careful about the level of oil. I did the exact same thing as you're doing and I started a thread about it. Do a search for this. The service manual is very vague about how much oil should be in the entire system and I don't remember exactly what I settled on but it might be in my old thread.

I flushed the entire system with the A/C solvent flush, and put in a new drier and expansion valve. When I installed the new compressor, I drained out all of its oil, then added a measured amount of the new oil to the compressor, but I didn't factor in that each 12 oz. can of R-134 had 1 oz. of oil for each 11 oz. of refrigerant. Therefore, I ended up with too much oil, displacing some of the space for the refrigerant, so the pressures went up and I had to stop adding R-134. Ultimately, it was not as cold as could be so I needed to drain some oil and start over. I think some cans of R-134 can be bought without any added oil in them - read the label.

Edit: here's my old thread:
http://www.nsxprime.com/forums/showthread.php?t=137524

 

[NSX-Files]

Looks like 7 fl.oz.

Ah... but we have two condensers, and at least 6 or so lines/hoses. So that chart isn't really useful if you're draining the whole system of oil with a solvent flush. It would have you put in too much oil if you added 2/3 for every piece of hose or pipe.

 

[goldNSX]

Edit: here's my old thread:
http://www.nsxprime.com/forums/showthread.php?t=137524

NSX-Files, thanks for sharing your experience with outfilling you system with oil.
How could I forget this thread. I'm getting old.

One note: you should dry the lines with nitrogen 4.5 or higher (less than 10 ppm water), not air as air contains too much moisture. I'm not sure if you get all of it out while evacuation.
As for drying how long did you dry the components?
Another note: I would rather evacuate more than an hour because the NSX A/C system is about double the size/long compared to front engine cars.

The A/C service stations we use here empty the system and divide the freon and oil seperately. The rule of thumb is to add so much oil while recharging that has been evacuated. But our mechanics are lazy sometimes and don't have a look how much oil has been sucked out and just add 30 ml of oil. The oil is added seperately, the filled R134a doesn't contain any oil.

You guess that you've overfilled to about 10 oz of oil. How did you remove the oil?

The infos are indeed confusing, 2/3 per line? I don't think that the shorter ones contain that much oil. If think most of the oil is in the bigger (radiator-like) parts. Did you flush the evaporator? I leave mine in but I guess I can't flush it because of the expansion valve.

 

[LJSB]

I have read both threads and realize that you aren't really asking for help, that you enjoy tinkering, learning through trial and error and will figure it out eventually becoming more and "expert" as you go. Bowing out here.:smile: unsubscribed

 

[goldNSX]

Joe, what's wrong with learing and sharing experience? :wink: It's not trial and error like most 'experts' do IMHO until the whole system blows up and I have to pay the bill. It's more the Ayrton Senna- or Alain Prost-way to understand how things work and how to improve it than the Nigel Mansell way who only drank beer, didn't test-drive his F1-cars and went on the golf-course instead.