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BMW e30 System restore

c130 on Tue September 11, 2012 1:22 PM User is offline

Year: 1990
Make: BMW
Model: 325i
Engine Size: 2.5l M20
Refrigerant Type: R12
Country of Origin: United States

I purchased this e30 last year and have all the service records since it was new. The AC system had been repaired in 2007 and was functional until a few years ago. I checked the compressor clutch and compressor by jumping it. Both seem to work, apparently the system leaked out. I pulled a vacuum on the system several times for up to and hour to purge it the best I could.

I pulled a leak check on it from the low service port and the system would hold unless I took the high port cap off. I removed the high port valve, which came apart when removed. I had to use a special tool with reverse threading on my valve tool to remove the seat that remained in the port. I then reinstalled a new valve.

I purged the system again for quite a while then performed leak check again, one from each port. The system is tight; it was able to hold 20”hg on the system for over 24 hours with the service caps removed.

My original plan was to convert the system to R134a; according to BMW the system is fully compatible already for R134a. Only the receiver/drier and port adapters need to be changed, plus a switch installed receiver/drier. After reading how inefficient the R134a systems have been in these cars do to the size of the serpentine flow condenser, I have had second thoughts. I could put in a larger parallel flow condenser but there is not much a whole lot of extra room for this and I would like to keep the car fairly stock.

Since the system is fully intact I thought I should maybe keep it R12. Since there are a few cans of this for sale in the area it would be worth a shot. Get the Freon and compatible oil (mineral oil type if I am not mistaken). Figure out how to get oil in system (approx 5.4oz) and service it up. I then thought that since the system has not been operational for a few years it probably needs some cleaning first as not to harm anything in it.

My thought process is this:
- Remove compressor; Clean and replace oil.
- Removed Condenser and accessible hard lines and hoses; inspect and flush them out.
- Run flush/solvent up into Evaporator Valve and into Evaporator, as to not to have the remove the dash.
- Install new o-rings and receiver/drier.
- Purge system again on vacuum.
- Leak check again for 24hrs on both sides.
- Service system with 2.1 lbs of R12 (3x 12oz Cans)
- Perform system check.

About me: I am an FAA Aircraft Maintenance Technician and a Flight Engineer by trade, so I am familiar with the operation of AC systems (Just not my specialty). I have also been working on cars for nearly 30 years and have brought a few R134a systems back to life after my wife complained about it. Cracked condenser on one and another never found out what was wrong. I just replenished system and all was well. Another had a leak and I could not find it anywhere, even used an UV dye kit.

I have the Following equipment:
-A full shop of most mechanics tools (He who dies with most tools wins)
-R134a Gage set
-Vacuum adapter for my compressor
-UV Glasses and Light Pen
-Master Cool AC System Flush Kit
-Factory Air AC Flush/Solvent
-Borrowed set of R12 Gages (High Side Gage inoperative), hoses, and can tap. Noticed the hoses are the same between the R134a and R12 gage set ups. You just put the port couplers on the ends of the hoses for the R134a.

My question is to the professionals, is my thought process sound to restore the R12 system. Should I bite the bullet and convert the system to 134a and deal with the lower output, or go to a non-stock condenser.

Edited: Tue September 11, 2012 at 1:30 PM by c130

TRB on Tue September 11, 2012 2:23 PM User is offlineView users profile

Stay R12 on that vehicle is my suggestion.


When considering your next auto A/C purchase, please consider the site that supports you:

mk378 on Tue September 11, 2012 9:47 PM User is offline

If there was any pressure left when you started, the system should be clean inside and the oil is still there. In that case you could just go with a new receiver drier, add UV dye, and a charge of R-12. I suggest a static pressure test with inert gas or 134a to be sure there's no leaks before committing to charge R12. Some things hold vacuum but leak under pressure.

Edited: Tue September 11, 2012 at 9:48 PM by mk378

c130 on Thu September 13, 2012 11:14 AM User is offline

Ok, thanks Guys. Sorry been busy. Will try to get a hold of some Nitrogen or Argon and pressurize the system. What do you think as far as a static pressure. Not sure how I would get the system up to normal pressure without buying a high pressure bottle and regulator. I was thinking using the High port using the Master Cool Flush kit and put 100psi of Nitrogen in that way. Cannot find online what the bottles max pressure rating is.

My Air Compressor has two styles or water removal before the regulator. One just a drop port for draining and a water removal system from the Regualor/Moisture removal kit I bought for it. The compresser itself is rated to 10.3 cfm @ 90psi and Maximum of 135psi. Do you see any problems just pressurizing the system that way?

c130 on Mon October 15, 2012 9:36 PM User is offline


Pressure checked system. Although my aparatus had some leakage so I figured the system was ok.

Charged system with one 12oz can of R12 and got 40 degree air coming from ducts at speed and mid 70s outside temperature.

Even over two weeks later, it was quite chilly in the car coming home from work with temps in the 80s.

Thanks all

mk378 on Tue October 16, 2012 9:52 AM User is offline

Put in the full charge. With just one can the oil isn't going to flow properly and you risk compressor damage.

roxannedetierro on Tue November 06, 2012 4:55 AM User is offline

I would recommend you just go buy an e30 M3. Finding one that is not a showroom queen and has been modified should be fairly simple. That seems like the end result you are looking for.

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