I know this question has been asked and answered for a 97 E320 recently, but I have a few questions of my own. The prevailing opinion seems to be that the correct oil is the Double End Capped PAG 46 oil, but the listings at Autohaus imply that the oil used depends on what brand of compressor one has. Is that accurate? If so, how would I determine which brand of compressor I have, and thus which oil?
My local dealers want approximately 51 dollars for an 8 ounce bottle of AC compressor oil, and claim that it's a proprietary mercedes special brew of lubricant.
$51 for 8 ounces? That must be some really special stuff. Consider that none of the system is actually made by Mercedes, and you see how special the oil must be. It's possible (perhaps even likely) that the M-B oil is not end capped.
ackits.com sells DEC PAG and it's nowhere near that price. You almost certainly need 46 Cst oil. What kind of compressor do you have on there? It should have a label with the brand and model number. My '96 carries a Denso.
About the only thing that needs a heavier oil than 46 Cst is a GM compressor. These were installed on some older models, but I don't think ever on the W210.
When I flush the system with the DEC PAG oil, do I need to worry about any of the old residual oil mixing with the new oil? I'm assuming the original oil in the system is non DEC oil, so do the two play nice together?
DEC PAG will mix just fine with non-capped PAG oil.
But the problem with non-capped PAG is the tendency to absorb water from the atmosphere. The oil bonds very tightly to the water and cannot be released without high temperature (your vacuum pump alone cannot do the job). The more water absorbed, the higher the gelling point of the mixture. If the oil gels due to the cold refrigerant in the evaporator, your compressor will not be long in this world.
Thus you must work very quickly and ensure that all open connections are tightly capped.
You don't want to flush the entire system with PAG oil; just the compressor. Yes, you will find that it is next to impossible to get all of the old oil out during the oil flushing. Be sure to remove the crankcase oil drain plug (next to the electrical connector) to get the oil out of there, and be sure to add oil there before mounting the compressor in place.
The rest of the system must be flushed with a solvent (preferably one made for the job) and purged with lots of dry compressed air or nitrogen. If you flush the compressor with oil and flush the rest with solvent (and purge), you can simply replace (nearly) all of the oil.
know what the problem with your a/c is,but if you don't have the proper tools to pull a vacuum and replace the lines that get contaminated and you are wondering if old oil can be mixed with new,have a pro do it,properly or say good by to your a/c system.
__________________
Mercedes Benz Lyrics
Artist(Band):Janis Joplin
"Oh Lord, won't you buy me
a Mercedes Benz
My friends all drive Porsches
I must make amends
Worked hard all my lifetime
no help from my friends
So Lord, won't you buy me
a Mercedes Benz"
That's it
"The Edge... there is no honest way to explain it because the only people who really know where it is are the ones who have gone over."
ohlord
However, I think we need to give Purple the benefit of the doubt, and assume that he's here to find out what he can do by himself.
I did purchase a new vacuum pump for my recent AC service work. Also a new flush kit. Together, that's about $500. Cheaper pumps and flush kits are available, but I figure that I'll use these again. The flush kit can also be used for the heat exchangers in a radiator (oil or transmission coolers).
Arizona Mobile Air (which sells a lot of AC stuff by mail-order) has a very nice AC forum here:
Lots of good browsing material there. Also, you can ask a question without getting jumped on too badly. About the only thing that gets a rise is the use of sealers or hydrocarbon refrigerants. I don't think we need to worry about hydrocarbons for replacing the 134a in our cars, since the system really does work well (as opposed to models from a decade earlier). As for sealers, avoid them like the plague they are. The same goes for so-called o-ring conditioners or anything else other than PAG and R134a. Refrigerant with magic extras isn't sold at the parts stores because it works; it's sold because it sells.
Of course, you can also ask pointed AC questions here. I know that it isn't lost on you that you need to perform the proper services to keep the system intact.
You have a good point ohlord, and it could be that I'm about to make a very expensive mistake, but unfortunately, sometimes the only way we learn is by doing. I don't actually have a vacuum pump of my own, but Autozone rents them out.
The problem I'm having is that the AC is not cooling. It originally exhibited itself as one side blowing hot air and the other blowing somewhat cold air. I thought it was a duovalve failure so I tried cleaning the duovalve to no avail. The problem got worse until both sides were blowing hot air. I had the system evacuated and recharged, after having tried adding some refrigerant myself (adding refrigerant didn't solve my problem). The mechanic who did the evacuation and recharge indicated to me that while the system was successfully holding a vacuum and there was no leak, the low side and high side pressures were the same. His suggestion to me was that it was either a bad compressor or a bad expansion valve (either the compressor was bad and not compressing, or the expansion valve was stuck/clogged, preventing one side from getting pressure). I've ordered an expansion valve, the O rings for the expansion valve, a receiver drier, and the hose assembly from the receiver drier to the AC condenser. My intention was to replace the above parts, flush the system, drain the current oil in the compressor and replace it with new PAG 46 (also ordered), get everything back together and cross my fingers. As things are now, when I go into the diagnostic mode on the AC, with the temperature setting on LO on both sides, the pressure goes from 7 bar up to 9, sometimes 10, but never higher. The compressor is engaging, but things aren't cooling and the high side and low side are not getting pressurized.
Thus was my logic for trying the expansion valve before giving up and going the compressor route.
What are the pressures on the service ports when the compressor is running?
It sounds like you are very low on refrigerant, but there isn't enough information to make an educated guess. If you are low, you need to find out why.
I'll have to hook up some gauges and post those values tomorrow since I can't remember, but considering the system has been recharged and there are no leaks they could find, I would assume it's not low.
I connected the gauges the afternoon and ran the car with the AC on for a while. Here's what I got:
I'm attaching a picture of the gauges after the car has been running about 15 minutes with the AC on. In this photo, the pressures are not exactly equal as I mentioned before, although for most of the time right before this picture was taken, they were equivalent to what the high side pressure is showing in the picture (~150 PSI)
Last edited by purplegrog : 08-28-2008 at 08:43 PM.
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