Larry, thx for the response. so what's the noise got to do with flushing? I think you lost me there.

The system was working fine until one day some intermittent noise that sounded like the clutch trying to engage, then it would not engage at all. a quick check by an Indi verified that the AC would not engage because there was no freon. Further verified that compressor was leaking badly when tested for leaks.

any particular supplier in EBAY that you have used in the past?

My question goes to the health of the compressors innards. If it is healthy but it leaks, then you should have a clean system that will not require flushing. If when turning the compressor by the front clutch portion it feels rough or if it was noisy, then you may have debris from the failed compressor in the system to flush out. If that were the case and you didn't flush, then the debris would destroy your new compressor.

If it is only leaking, still turns smooth and made no noise, then you should be good to go without flushing.

I can't remember who the vendors were. It's been a couple of years since I replaced one. The main thing is that these compressors rebuild well as far as I know. There are some others such as the old R4 that should be avoided in rebuilt form.

One of the few I've read good things about the rebuilds from is Four Seasons.

I don't know who might carry them on eBay, but I did locate their parts on Amazon, and was surprised that they were at least reasonably priced, though not bargain basement cheap.
To find their part numbers, just use the catalog on the site, and then search the PN on amazon or ebay. Most don't seem to list the MB as an application on the ads, but it cross references on the manufacturer's site.
http://www.4s.com/Online%20Catalogs-eCatalog/Content.aspx

__________________
-Josh
Testing the cheap Mercedes axiom, one bolt at a time...

If the Four Seasons brand is good, then they have drastically improved over the last several years. They used to justifiably be called "Four Seizin's."

I'll qualify the statement with the disclaimer that I have no personal experience with the brand, though I was planning on ordering a pump, receiver drier, and expansion valve shortly, assuming that I can't find a shop that I trust to do a shaft seal replacement on my SD's R4 pump.
I'm also debating the virtues of converting back to R12 while I'm in there, but not sure I want to go to the effort of that thorough a flush, as well as expending that much of my limited r12 stock, not to mention trying to get the idiotic fittings off.

I got the info leading me to read up on Four Seasons from my father who is a fleet mechanic for one of the Oregon state fleets, and he's generally not led me wrong on auto maintenance topics.

__________________
-Josh
Testing the cheap Mercedes axiom, one bolt at a time...

any suggestions on where to get a set of R12 manifold gauge set? any reasonable vacuum pump to purchase or should I go for a rental?

I don't know if you are on a strict budget or not.

If you're on a budget R12 gauges can be had really cheap at garage sales, ebay or lots of places. This is something that's been produced for over fifty years and in the car world, virtually obsolete for many people.

For a budget vacuum pump, go to an appliance repair shop and they will sell you an old refrigerator compressor for probably $5. Solder a 1/4 inch inverted flare fitting on the inlet and you've got a decent vacuum pump. If you want to get fancy make a frame with a handle and weld a bung in the top so you can change oil. I used a pump like this with great success for a number of years before getting a single stage wet vane.

If you're NOT on a tight budget, there are numerous online sources for a/c tools. The one that I've found with best prices and good service recently is tooltopia.com.

Also if time means more than saving money, you can get all this at your local supply house that caters to the residential/commercial HVAC service trade. The gauges and vacuum pump are both exactly the same equipment that these guys use because it is also used on R22 and R502.

Hope this helps.

i saw this on ebay for $42 - guage with vacuum pump? is this complete set? or am I missing something? is this any good?

http://cgi.ebay.com/ebaymotors/R12-R134a-R22-R502-AC-MANIFOLD-GAUGE-SET-w-vac-pump-_W0QQcmdZViewItemQQhashZitem335d0d3fb0QQitemZ220604481456QQptZMotorsQ5fAutomotiveQ5fTools

That air-operated vacuum pump is not strong enough to evacuate an AC system. You need a oil-submerged vane pump, preferably dual-stage, but single-stage will be a whole lot better than the air-operated pump.

You might also see if any of your local auto part stores rent vacuum pumps.
I saw that at least one local chain does.

As to where to get R-12 gauges, I got mine off of Craigslist for $20.
I couldn't complain about it too much. No idea what brand, but they seem to be a solidly built set, marked as Made in USA as the only script other than the range markings.

__________________
-Josh
Testing the cheap Mercedes axiom, one bolt at a time...

are there any other parts that would make sense to replace while working on the AC? I will replace the ac compressor, drier and expansion valve. flush, evacuate and re-charge with R12 is also in order.

also, aside for the R12 canisters, is there some other oil that I need to add? how much R12 do I need to charge a 91 560 SEL AC?

I am in the process of re-charging R12, but now I am stuck and need some help.

Here is a summary of what I have done so far:

Replaced compressor (reman), drier, pressure switch and temp switch, and all o-rings under the hood.

I flushed the high side which came out clean. i then decided to leave the low side alone. I did not replace the exp valve. this could have been my costly mistake.

I put about 7.5 oz mineral oil in the compressor, and about 0.3 oz in the drier, then assembled them back in.

I pulled vacuum overnight, closed the manifold valves thereafter for about an hour and observed vacuum held with no problems.

I then started charging with the first can. After about 2 minutes with the first can charging and engine off, I observed the low pressure went up to 90 psi and high side at 40 psi. I noticed there was some more left in the can so I dipped the can in hot water and it continued to charge. at this point I am thinking the low side is showing pressure too high. I decided to proceed with the second can, turned the engine on and heard the compressor engaging, but no cold air. I did not hear or see the 2nd can discharging at all. I thought it is because the pressure inside the system is now too high compared with the pressure inside the can.

any insights would be appreciated.

larry, you mean open both high side and low side manifold? I am using the yellow hose of the manifold guage set to connect the cannister. If I open both sides, wouldnt the R12 also go the high side? I think I am confused. kindly explain further.

lol @ $1200 to convert to 134A, a mechanic sure ate well that month thanks to you. R12 is perfectly legal to own, use, and purchase.

I see the 12oz cans of R12 hit around $25/ea during the summer (ebay, CL, etc) as opposed to around $10/ea for the 134A at the auto stores. Over four cans you are spending a whopping $60 more for refrigerant when purchasing in the heat of the summer. Buy it off season and buy in bulk, you will save piles... like I do.

There is simply no good reason to convert these cars to a different refrigerant. I tried Freeze 12 in my 300SEL, so say it does not perform well is being nice.



My tools came from ACkits.com

__________________
I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]

I managed to get (3) cans (12 oz) to charge. the 4th one was taking forever, and i think there is still a little left. the site glass is still cloudy and lots of bubbles so I think I need more.

How many cans do I need for a complete re-charge for a 560 SEL?

I found it quite long for one can to charge. I had to use hot water to get the process going. And even with hot water, I was not able to get the 4th can totally consumed with more than 2 hours trying.