A/C System Tear Down and Rebuild

My wife's 1988 190E 2.3 A/C finally gave out.  I had attempted half measures at repairing it it the past.
 - Refill with R12 (when it was available)
 - Convert to R134A, by simply installing one of those quick kit found at PepBoys (or where ever).
 - Fixed leak, by removing all the hoses, replacing all the O-Rings (except for the compressor), flushing the lines and replacing the receiver/dryer.
After all that, it just never blew icy cold air.  I just assumed that was how it was..  Then this summer it started blowing hot air again.  Previously, I had installed a leak indicator dye so I could easily locate any future leaks.  This time I could see it was leaking from the compressor's front seal.  So this time I decided to tear it all down (except for the evaporator, the exchange unit in the dash).

Jobs Performed:
 - Remove Compressor, all hoses/lines, receiver/dryer, condenser and expansion valve.
 - Replace all the compressor seals.
 - Flush condenser,  evaporator and all lines/hoses.
 - Replace receiver/dryer.
 - Replace compressor oil
 - Replace all o-rings
 - Evacuate the system and refill with R134A

The compressor found in this car was a Nippondenso 10P15C and is found in various other manufacturer/model cars (Ford and Porsche for instance).  The manifold (where the lines connect to the compressor) is probably the only thing that's different. 
Parts - I ordered the seal kits, o-rings, flush and PAG oil from www.centuryautoair.com they were very helpful and processed my order quickly. 
Oil - This compressor required PAG-46 and through some research (Googling around) I figured is required about 4oz.

Reference Material

Googling around I found plenty of helpful information:
 - Rebuild method for Nippondenso 10P15C A/C compressor as on a Toyota Supra and Rover 800 / Sterling. 
    Article by  Peter Cohen  http://homepage.ntlworld.com/simon.stirley/htmlman/acpump.html or the PDF
 - Acticle by Rod Walter doing a rebuild on a Porsche 911 compressor rebuild.
        http://members.rennlist.com/elsies911pal/nippondensorebuild.htm or PDF
 - Presure/Temperture Chart http://www.autoacforum.com/aacf/ptchart.cfm
 - A/C Circuit - PDF 

Special Tools/Supplies:

 - Vacuum pump for evacuating the system w/oil.
 - R134A Pressure gauges.
 - Set or Metric allen sockets
 - Torque wrench
 - Assortment of A/C O-rings (CenturyAutoAir or similiar, although go to MB for the manifold-line o-rings.  They have little grippy things on them that will hold them in place while you're install the compressor)
 - PAG-46 Oil
 - 3-4 cans of R134A
 - Aerosol System Flush
 - Shaft Seal kit (and full gasket set if you do a total tear down).
 - 1-2 cans of System Flush
 - New Receiver/Dryer (R/D)
 - Air Compressor for blowing out lines.

Disclaimer

The following procedure was done on my 1988 190E2.3 and I can't say if this procedure will apply to other years and/or models.  This procedure worked for me and anyone else should use this writeup only as a reference.  

Procedure  (Various pictures)
First, my system was completely empty due to the leaky shaft seal.  Otherwise you'll have to have the system properly drain by a A/C professional. 
I chose to remove as much of the A/C system as possible, so I could easily flush and clean out all the components as I could.  I also, replaces all the o-ring's at all the couplings.  
Note: Even though the R134A conversion kit says it's compatible and neutralizes any old R12 remaining it the system, I found o-rings that had started to deteriorate after my first conversion attempt.   So if you don't plan on going through everything, skip some (*) of the next section.

Remove all components
First if possible, take digital photos on the disassembly process to help in the reassemby.  If digital camera not available, take careful notes.
- I started by removing the radiator fan and shroud to give more room to work.  
- Then loosen and remove the serpentine belt. 
* Then I remove the plastic grill beneath the windshield.  This is necessary to gain access to the expansion valve and evaporator.
- Remove the left headlight assy.
- Remove plastic shield that is screwed to the frame adjacent to the A/C Compressor.
* Use two large adjustable and disconnect the low pressure hose (large hose/line with lo-press fitting) from the fuel-cooler.
 (Note: gauge/filler fittings locations - Hi-Press fitting at front of car next to condenser, Lo-Press fitting on large line on top of left wheel well.)
Note: Expansion valve.  This is the aluminum block of metal that connect the hi/lo pressure lines to the evaporator, located behind the firewall, below the windshield.
* Disconnect the Hi/Lo Press lines from the expansion valve by removing the screw that is located between the two line and is screwed into the aluminum block.
* Remove straps that secure these lines to the firewall/body of car. 
- Label and disconnect wires from sensors on the Receiver/Dryer.
- Disconnect the both Hi-Press line from the Receiver/Dryer. 
   Note: Always use two wrenches when disconnecting lines,  one to hold one side stationary as the other end is loosened/tightened.  Otherwise will twist/damage lines.
* Remove both Hi/Lo Press lines from the car.  
* Remove Expansion Valve by loosening and removing the two screws that secure the valve to the clamping plate behind the valve.  Be careful to not drop the screws and clamping plate, which just sets on the two line coming out of the evaporator.  
- Disconnect Hi Press lines (short line from R/D) from the Condenser. 
- Remove R/D. (Note: replace with a new one)
* Disconnect/Remove the hose between the Condenser and Compressor.
- Removing Compressor
  Note: The fuel cooler assy, that is incorporated into the Lo Press circuit, is mounted to the left side of the engine and I did not remove it.  It has a flange that bolts to the compressor manifold.  The manifold has two ports on it Suction (low pressure) and Discharge (hi pressure).
- Remove the bolt that connect the flange to the compressor manifold.
Note: Four long bolts mount the compressor to the engine.  Three of those bolts screw into the compressor mounting bracket.  The fourth (rear, I think, outer) has a nut that has to be held while removing/replacing.
- Remove the little lower bracket that is attached to the front-inner compressor bolt and two oil pan bolts.
- Remove remaining three bolts and lower compressor from car.  You may have to wiggle it around a bit.  And be aware that there is oil that may leak out of the manifold ports in the process.
* Removing Condenser
   The Condenser is held in place by a couple clips.  You may be able to remove by simply loosening the radiator and sliding the condenser out.  I also removed the Aux Fan Assy (for cleaning) and horn assy to make is easier. 

Cleaning/Flushing

With everything out of the car, I proceeded  with cleaning/flushing the lines/hoses, condenser and evaporator. 
- For each of the lines, I plugged one end and filled through the other end with A/C System Aerosol Flush.  Let it set for 20-30 mins, drained and blew out with compressed air.
- For the Condenser, I set it on end and filled with flush, let set, then drained and blew out.  Then repeated.
- For the Evaporator, I go a couple lengths of hose and pushed them over the lines so flush would not leak all over the car. Then filled with  flush, let set, drain and blew out.  Then repeated.
- NOTE: You can not clean the R/D, it must be replaced.
- NOTE: It is also suggested, that the expansion valve be replaced.  I cleaned mine with flush and carefully blew clean.

Compressor Disassembly/Resealing

 I used the articles listed above as my guide through this process.  This is what I found when I disassembled my compressor.  (refer to my pix) 
First a little background on this system.  Since the R134A conversion, every summer season for the past several years, I've had to refill the system.  And just the past year or two, the compressor started making noises and blowing just cool air.  This season it was so noisy, I decided to pull it all apart and have a look.  Fortunately, I found several articles on this process, which is not detailed in the MB Shop Manuals.  
After I opened the compressor up I could see some minor scoring on a couple cylinder wall and some damage to the cam (what drives the pistons) surface.  I decided to replace the compressor with one off a car from a local auto recycler.  If possible, get one that is still on the car and connect to the system.  At least you should be fairly sure it wasn't filled with water or something.
Then I, disassembled and resealed this used compressor, per the above procedures.

Reassembling the System

(in process)

Evacuating and Recharging the System

(in process)

Observations and Results

Well it's been a couple months now since this work and this summer has been extremely hot.  I've kept an HVAC thermometer  in the air vent to monitor the temperature and on the hottest of day, its blows an icy 55F degrees. 
One of the problems with just adding refrigerant that has oil included, is you have no way to know how much oil is already in the system.  If you overfill the oil, that can result in damaging the compressor, which I think may have happened in my case.  When overfilled, oil can get into the compression chamber which will damage the compressor.  The only way to know how much is in the crankcase of the compressor, is to empty it and refill with the exact amount required.