PAG Oil Quantity / Type and Flush Review...Please Read! - PeachParts Mercedes-Benz Forum

slimak9 · #1 07-09-2007, 05:06 PM

W140 1992 400SE.

The charge line running from the Evaporator to Compressor cracked open near the Compressor, so after discovering a new line is well into $400, I removed it and had the rubber replaced on my current line for a few dollars.

When I removed the line from the compressor about 3 weeks ago, a good amount of oil leaked out. Guessing 2-3oz.

Now with the line repared, new receiver/drier, new o-rings for each hose connection (8 total), blue nylog for the treads, a borowed 6CFM Yellow Jacket Vacuum Pump and Guages, Castrol PAG Oil - ISO 46, and a couple cans of Supercool Aerosol Flush I'm ready to put it all back together.

Since the system has been opened for 3 weeks (moisture entered into the remaining oil) and I don't know how much oil leaked out (while disconnecting hose and over the comming months when only a small leak was present), I am going to flush the entire system.

My questions to those who may shed some light are:

What is the correct quantity of PAG Oil for this system (R-134a with No REAR A/C), on ALLDATA is states:
1. 160 cubic cm for new oil fill in compressor
2. Condenser
Renew. 20 cubic cm of new compressor oil.
3. Evaporator
Renew. 40 cubic cm of new compressor oil.
4. Receiver
Renew. 10 cubic cm of new compressor oil.
5. Suction line from evaporator to compressor and compressed air line from compressor to condenser
Renew. 10 cubic cm of new compressor oil for each.

Total 250 cubic cm = 8.45oz.
Does this sound correct???

Secondly, is PAG Oil - ISO 46 the correct viscosity?

Third, what is the correct way to flush the Compressor (Spray in one and out the other OR rotate while flushing???)

Fourth, what is the correct way to flush the Evaporator (Top to Bottom OR Bottom to TOP???)

Finally, I must be blind, but I cannot find the A/C Label on the vehicle anywhere....to verify the refrigerant quantity, can anyone tell me where its hidden??? ALLDATA states 1300g (w/o Rear A/C for R-12)= 2.86lbs, I know to put in 80-85% of this number into my R134a system.

Thanks for all your input, feel free to add what I may have failed to ask or specify. Thanks again.

slimak9 · #2 07-11-2007, 04:23 AM

Well I determined that the A/C identification sticker is missing, ordered a new one at the dealer.

slimak9 · #3 07-15-2007, 10:00 PM

Anyone??? Confirm quantity and type.

Thanks.

dpetryk · #4 07-15-2007, 10:13 PM

Answers;

1. 8 oz. sounds right.

2. PAG 46 is correct.

3. Flush the compressor by removing it from the car. Add some flush, rotate, and drain everything you can using gravity. Follow up with a good dose of dry air to evaporate any flush remaining. Repeat until no oil residue is carried out with the flush. Very important to not leave any flush in the system since it will contaminate the refrigerant.

4. Flush the evaporator both ways. Flush until it flows clean. If you are only going to do it in one direction, then go reverse flow. The expansion valve must be removed before flushing the evaporator coil.

5. I cannot confirm the refrigerant quantity but the 126 systems use 2.9 lbs. so 2.85 sounds like the right number. I have the charts with the numbers at my office. I will check tomorrow.

myarmar · #5 07-15-2007, 11:01 PM

This is from 92 600SEL

slimak9 · #6 07-16-2007, 02:41 AM

Dave, is the Expansion Valve mounted right on the Evaporator? Would this mean the removal of the Evaporator, which as many know is easily at 20+ hour job?

myarmar, thanks, I believe that is the same part # ID sticker I ordered. Should be in by Wednesday, when I'll have flushed everything and be ready for Refrigerant.

dpetryk · #7 07-16-2007, 12:40 PM

Yes the expansion valve is mounted on the evaporator connections. You don't have to remove the evaporator but its probably not in an easy to get at location. I have no experience with your chassis but on the 126 it is not easy and almost impossible on a 107 without removing lots of other stuff to get at it.

Once the expansion valve is off, attach two rubber hoses clamped to the evaporator connections and blow the flush through the hoses and evaporator. Its messy so its important to get the hoses outside of the car when you do that.

Depending on the condition of the oil you may not need to flush the evaporator. If the oil was clean its probably not necessary. Better if you can flush but its a lot of work. If the oil is dirty or the compressor shed a lot of trash do the flush.

BENZ TEK · #8 07-16-2007, 01:05 PM

Quote:

Originally Posted by slimak9

Dave, is the Expansion Valve mounted right on the Evaporator? Would this mean the removal of the Evaporator, which as many know is easily at 20+ hour job?

myarmar, thanks, I believe that is the same part # ID sticker I ordered. Should be in by Wednesday, when I'll have flushed everything and be ready for Refrigerant.

You will have to remove the wiper assembly and lower drain cover that sits under the wiper transmission. Then the expansion valve is pretty easy to get to.

myarmar · #9 07-16-2007, 05:16 PM

I don't think it would be possible to remove and reinstall expansion valve. Here is a picture taken during my evaporator job.
Mike

dpetryk · #10 07-16-2007, 05:29 PM

That looks like a day at the beach compared to a 107 or 126.

BENZ TEK · #11 07-16-2007, 06:40 PM

Quote:

Originally Posted by myarmar

I don't think it would be possible to remove and reinstall expansion valve. Here is a picture taken during my evaporator job.
Mike

Theres one 10mm bolt and two 3mm allen screws. Its not hard to do but will take some time to get down to it!!

slimak9 · #12 07-16-2007, 09:23 PM

Thanks to everyone, I got the wiper assembly out, and the Expansion Valve has been removed.

I ordered a new expansion valve, as I've read in the past, its a worthwhile item to change, and that I already have it removed.

I noticed 4 O-Rings used at the Expansion Valve, the dealer said they come with the Valve, would anyone recommend using Nylog at those joints along side with the O-Rings. The joint are Not Threaded, but simply a slide in, what are your opinions?

Dave, I'm going to have the flush the evaporator (whether clean or not) as I have not idea how much oil is left in the system. You also mentioned flushing the Evaporator both ways, would you recommend the same for the Condenser?

slimak9 · #13 07-16-2007, 09:39 PM

Another question...

I have a couple bottles of this leak sealer:
http://www.acsource.com/index.asp?PageAction=VIEWPROD&ProdID=1244

Its 2oz. and I wanted to add it into the system once its flushed and filled with 8.5oz. of PAG Oil. What are people views on this? Should I use it? Should I use it, minus 2oz. of PAG Oil? Or stay clear?

I would split it between the Condenser and Evaporator.

Thanks again,

dpetryk · #14 07-17-2007, 09:56 AM

When ever I am doing a flush job, I always flush the individual A/C components separately. Hoses, coils, compressors. I flush until it comes out clear. I chase it with a lot of dry (-40deg. F dewpoint) air. Bi-directional flushing just gets the junk out faster and sometimes it can get stuff that might have a hiding place in one direction. Not really necessary. It depends on how dirty the first pass is. Be sure to use flush approved for A/C systems. I know people who use paint thinner and all sorts of other stuff. Not a good idea. They can leave hydrocarbon residues that react with the refrigerant.

I use a flush gun. You put 1-2 cups of flush liquid in it, connect it to your air source, put the nozzle into the thing being flushed and let it go. The flush is under 100 lbs of air and it rips through the coil vary fast. The air continues to drag out the remainder of the fluid. Keep the air on until nothing is coming out. Repeat until clean.

I do not use any dyes or stop leak additives. I find the leak with a sniffer and fix it. The only exception to this rule in my book is if you have an evaporator leak. As a last shot I use only one brand of stop leak and only on evaporator leaks. The problem with stop leak is it reacts with the air & moisture to form a plug at the leak site. If you have to open the system for service guess what gets in? If you open a system that has stop leak in it, you must flush no question.

I use the green O rings they are compatible with R12 & 134. When handling the PAG oil, keep it capped until the last minute. It sucks up moisture from the air quite quickly. Hold a vacuum for 4 hours to evaporate as much moisture as you can.

Advantages of flushing;

1. It changes the oil - just like your engine needs new oil - so does the compressor.

2. You know exactly how much oil & refrigerant is in the system.

3. Removes any acid and moisture that may have accumulated. PAG oils are very hydroscopic they absorb moisture like desiccant does.

4. Any system that has a leak - by definition has moisture in it. You have the opportunity to replace the dryer. If refrigerant can get out - then moisture can get in.

5. Having done the job right helps you sleep better at night.

slimak9 · #15 07-18-2007, 01:52 AM

Thanks Dave for all your input.

I absolutly want the job done right. I just completed removing the compressor (wow! any less room and the radiator or sway bar would have to come out, thankfully removing the plastic shield behind the radiator DID IT!)

Also,
1. The hose from the Dryer to Condenser is out.
2. The hose from the Compressor to Condenser is out. (wow! was it ever tight/seezed to the fitting on the Condenser, what a work-out!)
3. The Dryer is out, new one arrived.
4. The Expansion Valve is out, new one arrived.
5. Abviously the Low Pressure/Fill hose is out (the one that originaly cracked and started this mess!)
6. The rest of the hoses are just disconnectedm but not out (way too much work, will flush them the way they are installed.)

I spun the Compressor w/ Gravity and I gota say not much oil came out, approx. 0.5oz. (most of it must have leaked out while the hose at the Compressor was faulty).

Now I just have to pick up 2 more O-Rings for the one side of the Expansion Valve (Forgot), 1 O-Ring for the Switch on the Dryer, and get a refill of DRY AIR.

Then flush the Evaporator, Condenser, Compressor, plus all the lines.

I'm waiting to see the outcome, and hopefully this will end my A/C Wooes for a bit.

WOW, is Compressor Oil ever so expensive, I picked up a bottle of exactly 250ml OR 8.45oz. (funny to be exactly the amount I need for the system as per ALLDATA) for a list $72.55 (CND + 14% Sales Tax) = $82.71, (Part # 001-989-08-03) Can anyone in the US tell me what dealers there sell it for?