Hi,

So I am about to replace the dreaded expansion valve on a modified (R134a) system on my 1989 560 SEL (W126). Since the system has been completely empty now for almost a year, and not been run, I wonder about how much oil I should add.

Details:
* replacing Expansion valve
* replacing Receiver/Dehydrador
* evacuating system
* charging up with 134a

I am having a hard time coming up with specs. I think I need 36 oz of 134a, but I don't know the rest.

Interesting thing is that I just read the thread here on the R134a being sold with sealant in it. I'm glad I saw it before I went for it. I also realized at Target that all of the refrigerants sold with oil also have the sealant in it. So I am back down to using nothing but straight 134a, and squirting the oil manually into the system before closing it up.

The CD is confusing, and has contradictory information as follows:

manually check by opening oil port on compressor and fill to overflow
OR
Fresh oil in compressor: 170cc
OR
Add ref. to system above 200g (my case, because it's empty): 30cc
OR
Renew rec/dehyd. 40cc

Nothing about renewing exp. valve

What do I do? Do I just check the compressor oil port, squirt in till overflow, and add 134a without any additional oil in it? Or do I buy premixed 134a with oil in it (sounds dangerous to me now, by the way)? Or add in 70 cc (new refrig. 30cc + new rec/dehy 40cc)?

Thanks for any input!

__________________
Henry Bofinger
1989 560 SEL (black/black)
2001 Audi TT Roadster (silver/grey)

I am not an expert, but since you have received no responses I will offer some help.

Your biggest problem is that you have no idea how much oil is in the system. Additionally since the system was converted, was it properly flushed during conversion or just charged with 134?

If the car were mine this is what I would do; I would break all connections and flush thoroughly, thoroughly remove the flushing agent, replace all o-rings with 134 compatible ones, dump as much oil as I could get out of the compressor, put the correct amount of oil in the system by putting a few ounces in the compressor, a few in the condensor and a few in the evaporator as you reconnect everything (you need to research and find how much oil the system holds) replace the r/d last thing so that the time it is exposed to the atmosphere and the open system is minimized, be prepared to evacuate as soon as you finish replacing r/d, evacuate and charge with 85% of the specified R12 amount. There should be a sticker somewhere under the hood that will specify the refrigerant amount.

If you go to: www.aircondition.com and poke around, you can find the oil quantity, or post a question in the forum and get the answer.

I said that if the car were mine this is what I would do. I take that back. If the car were mine I would flush and do everything I said, except I would put in mineral oil and charge it with R12. MB's just don't have the reserve capacity to cool very well with 134 unless you upgrade the condensor and even then there is no guarantee.

One more thing. I assume that you have found and repaired your leak. You will certainly want to do that before going to all this trouble and expense.

Best of luck,

The conversion was done recently by a professional, and yes, he had flushed the whole thing and out in the new oil. But there was a leak, and we did not know how bad it was until after the conversion. It cooled rather well for a couple of weeks until the system was dead empty, so I was not too disappointed with the 134a's performance while it lasted.

Well, with dye and the whole chazam we found one bad hose and the dreaded expansion valve. Those are the items I am fixing this week before refilling the system. That's why I need those oil numbers.

I did check www.airconditioning.com, and found nothing there yet, though my check was not the most thorough. Since there are so many Benz people here, I thought someone might know the exact number....

Thanks!

__________________
Henry Bofinger
1989 560 SEL (black/black)
2001 Audi TT Roadster (silver/grey)

I would add a very small amount of oil - a gas leak in an A/C system will only result in an insignificant amount of oil leakage.

I'd put at most and ounce or two to compensate for the replacment of the receiver/dryer.

You also need to ask what type of oil your "professional" mechanic used when he converted the system - there are at least two different types that could have been used.

Yes, now that we know the history, you probably can just evacuate and recharge. I would add no more than 2 oz. at most. Any time you have a leak like that after previously having the correct amount of oil, you are just operaing on guess work.

Good luck,

Thanks!

I'll go with the 40cc number then. Makes sense!

__________________
Henry Bofinger
1989 560 SEL (black/black)
2001 Audi TT Roadster (silver/grey)