I am new to this site and have purchased a 1980 240D. The work on this car has become a labor of enjoyment. I am going to replace the AC compressor, drier,pressure switch, and expansion valve. I am use to seeing a pivot bolt and slide channel this set up is different. How do loosen the AC belt ? It takes a GM radial R4 compressor and has been retrofitted with R134-A. Any do's and don'ts? Should I flush the system before or after replacing the parts and recharging?

Thank You jcj

The important question back to you is; WHY are you replacing the compressor? If it is due to leakage there is one answer to your question, but if it failed internally, there is a totally different answer to your question.

Let us know and we'll prescribe the correct course of action for you.

Good luck,

Thank You Larry... I was told that the compressor is shot and given a horrific price to replace it. I am a chef and always play with my food and love working on my car, so what the heck I will get the parts and do the work. I do not want to be a penny thrift and a dollar foolish so I am replacing the AC components that commonly fail. I am really uneasy about what are the do"s and don'ts when working on the AC system. I have had the system depressurized, now do I coat the fittings with refrgeration oil ? Should the drier will be the last thing I connect before taking to be flushed and recharged with R134 ?

Okay, that still doesn't answer my question, but here's the deal. If it is being replaced because of a leak, you could probably get by with simply replacing the compressor, filter-drier, evacuation and charge.

If, on the other hand, the compressor failed internally, then it has strewn all sorts of metal debris throughout the system. If this is the case, if you do not COMPLETELY AND THOROUGHLY FLUSH THE SYSTEM, the new compressor probably won't last fifteen minutes.

It sounds as if you must assume that it has failed internally. This means, you must break EVERY connection and flush, flush, flush it again, followed by a thorough flush and then finish up with a really good flush on EVERY component in the system. If you do not adequately flush and there is ANY debris left in the system it will destroy the new compressor.

Some folks think that the filter drier will catch such debris but it will NOT. This is because there is plenty of system PAST the filter, so the filter can't catch everything. Even if it were at the compressor inlet, it is only a screen and won't filter enough to keep the trash out of the compressor.

So, the procedure will be TOTAL dismantle of all components, flushing ALL components MULTIPLE times in BOTH directions, followed by replacing the compressor, using 134 compatible o-rings with nylog lubricant or at least coating with refrigerant oil, putting in the correct amount of oil, putting the new filter/drier in LAST so that it does not start getting soaked with moisture from the air, then THOROUGHLY evacuating the system and charging.

You MUST ensure that you get ALL the flushing agent out of the system.

The last issue is the 134. These systems have very little additional capacity. Since you lose about 20% of refrigeration capacity when switching to 134, these are not good candidates for conversion. You will have so much money and time in this system rebuild, going back with R12 would add very little as a percentage of the project expense. I would highly recommend going back to R12 and if you MUST use something besides R12, don't even consider anything except 134. Don't go to any of the junk refrigerants.

Good luck,

Thank You Larry.....I am replacing the compressor, drier, pressure switch, and expansion valve. I was told by A/C shop that I had a bad compressor( it was making some very rumbling noises) and was barely cooling. The only other parts I can think of flushing are the main hoses and condensor. Flush with air?

The bad compressor was probably caused by the sytem being converted to R134a but done incorrectly. You have the "black death"
Go here and read and learn.

http://www.ackits.com/

So if you had the system converted incorrectly you MUST flush the sytem to remove the debris and the mineral oil and R134a oil. since these oils can't mix they allow the compressor to run without proper lubrication which causes the "black death".

The flush is done with a flushing agent or mineral spirits then with a final flushing agent use if using mineral spirits. Buy a flush gun. You will need a compressor. You will have to flush everything in the system except for whats replaced. Flush the hoses, all of them. The condensor and the evaporator. Use new orings. Install the new compressor and a new Reciever dryer. Consider a new expansion valve. Its a small oriface and if not flushed completely it will be blocked. The evaporator is the most difficult because its in the car. But it must be done.

As Larry has said consider using R12 instead of R134. In the 123 you'll be happier.

Again read and learn on the ACKITS web site.

Dave

__________________
1970 220D, owned 1980-1990
1980 240D, owned 1990-1992
1982 300TD, owned 1992-1993
1986 300SDL, owned 1993-2004
1999 E300, owned 1999-2003
1982 300TD, 213,880mi, owned since Nov 18, 1991- Aug 4, 2010 SOLD
1988 560SL, 100,000mi, owned since 1995
1965 Mustang Fastback Mileage Unknown(My sons)
1983 240D, 176,000mi (My daughers) owned since 2004
2007 Honda Accord EX-L I4 auto, the new daily driver
1985 300D 264,000mi Son's new daily driver.(sold)
2008 Hyundai Tiberon. Daughters new car

dmorrison...Thank you ! ackits.com great reference. I am going to order their flush gun and go back to R12. Will I run into any problems being that the system was retrofitted to R134. Can I get away with not changing the condensor.