AeroStress

From AllData, it says the refrigerant oil capacity is 6.8oz / 200g / 200cu-cm. In my case, I have lost some compressor oil (due to a failed compressor) and do not know how much is in the system. In that case, it seems quite difficult to know how much should be in the new compressor when its it is installed.

From the following clip from AllData, what I gather is that the new compressor will ship with 200cu-cm, which is the total for the system. Then they say to remove 80cu-cm (presumably that is an assumed amount in the other components?). This leaves you with 120cu-cm in the compressor. I guess a minimum I should make sure I have 120cu-cm in the compressor and then maybe just assume that about half of the oil was lost (40-cm) and could then put 160cu-cm in the compressor. I do remember a Denso rep saying you should measure the fluid in the old compressor and make sure the new one has the same amount, since too much fluid can blow the compressor...but that assumed the compressor failed before leaking.

I guess I am just wondering if anyone has thoughts on this or how sensitive the compressor is to fluid quantity. Or maybe if there is a thought as to whether its better to go on the low side (maybe 130cu-cm) or the high side (maybe 180cu-cm).

JAGMAN1

I did this job about two years ago and had similar questions. I think the system is far more sensitive to underfilling the oil than over filling. So I would air on the side of too much.

For reference I followed the instructions and emptied 50 grams. If I had to do it over again, I’d have kept all of the oil in there and installed it.

BobcatBrian

Agreed. IIRC, an A/C system that is slightly overfilled with lubricant will not hurt anything and the only downside is that it may not cool as well as a perfectly filled system. But I don't know if it is appreciably different.

theprf

If you really overfill the oil it will suck an oil slug into the compressor. Since oil is incompressible the compressor will explode. Yes I have done this on a different car. There is no way to tell how much oil is left in it. The recommendations assume the system was working properly, of course who would be replacing parts on a system that is working properly? The absolutely correct way is to flush the system with solvent removing all the oil then refill with the proper amount. No one actually does that, we just guess at how much oil was lost and add that amount.

Also note that aftermarket compressors may have no oil at all inside, because the same compressor is used on different cars with different oil requirements.

Have you changed the receiver-drier? Might want to do that. It's probably blocked with congealed stop-leak. I believe these cars have the receiver/drier integrated into the condenser under a screwed in plug. I would also check high side pressure because stop leak can mess up the TXV, which can produce extreme high side pressures. That can blow out the compressor shaft seal.

AeroStress

Thanks...some good info there.

- My 2nd compressor failed very shortly (and suddenly) after putting the AC stop leak (after the original 2005 failed - perhaps just old). I originally attributed this to the goopyness of what I saw later when I opened it up, but maybe it was just the extra volume of fluid (the stop leak was 3oz but I don't know if it is a liquid or solid at room temp). I have some on order to do some lab tests with it though.

- A leak in the evaporator was the initial issue, which is a pain to replace. I figure if I have to replace that, I may as well just do the condenser, expansion valve, and compressor along with it...but that would be a big pain.

- I asked my local shop if they could flush it yesterday, but they said that isn't something they do. The other concern is that if I flush it, maybe the leak in the evaporator will come back. But maybe they can flush everything but that. I can try to call around but a lot of places hear Porshe and say no to anything.

- The recently compressor failure (compressor #3 - cheap eBay) is not because it stopped "compressing"...it is leaking oil (different than #2 which may have been a hydrolock). So who knows how much oil I have in the system (plus that stop leak).

- Read the AC gages yesterday and they looked good. Also its blowing cold air when refrigerant is in there. I pulled it out and ran a vacuum and it had a slow leak (presumably from the compressor).

- My HOPE is that if I put in a compressor (Denso OEM) it will work now (better quality compressor). And maybe the goop is cleared out enough from 2 compressor changes. Autozone said they have a 2 year warranty for any reason so I can always get a replacement if it fails. I hate to do that to them, but I do think its possible the goop has been cleared out enough since compressor #3 was working for several months at least....just a leak which I think may be due to low quality part and not necessarily junk in the system. I don't see why the stop leak would cause the compressor to leak?

- Oh, and the drier has never been changed. But I do have one and just got a slide hammer and plan on doing it this time (its in the condenser). That would be great if some junk came out with that. I suppose from visible inspection alone, I will know more when I replace those two parts.

JAGMAN1

Agree with all. Keep in mind that we typically find the failed component by searching for the oil stain. So some oil has leaked out. If I had to do it again, I’d air on the side of a bit too much.

AeroStress

I just saw this from the Dryer DIY AllData..I have wondered what happens when you put a vacuum. I suppose this means about 10% of the oil is lost when you evacuate and pull a vacuum? That is interesting since I had an evaporator leak before (very slow) so would just add refrigerant (after removing it all and pulling vacuum) every 6-9 months. I wonder if after a few times doing this, I lost enough oil for the compressor to seize.

theprf

Vacuuming the system won't remove more than a tiny bit of oil. They must be describing the oil that soaks into the dessicant.

AeroStress

FYI, you guys might find this interesting. When I removed the compressor, it only had 30g of oil in it. When fully charged and working, the system has 200g (120g of which is expected to be in the compressor from AllData). The compressor had been leaking fluid so this is to be expected, but it is surprising that it was still working (verified via temperature tests and AC gages...and also no indication of a failed AC other than the leaking fluid). This suggests it is quite tolerant to low compressor oil. Also why guessing at the amount of oil seems to work OK. Perhaps with this information, one might even too much fluid is riskier than too little...I actually think I failed the prior compressor due to excess oil.

Also, for the new Denso unit (precharged), I was only able to get out 100g. I was expected 200g like AllData indicated (and at least 120g)...but maybe its actually just 100g that came out and 20g still left behind (meaning this is only the amount indicated for a compressor only - and not the full system).

My current theory is that if the prior compressor was still running at 30g and the new on has 100g...I should be good just leaving it at 100g. I may add just a bit (like 20g) to be on the safe side though.