I have a 87 300sdl and would like to convert it to R134a A/C. I try to purge all old mineral oil from the system with compressed air but no luck. I only open up the reciever drier on both end as I need to replace it anyway. I really do not want to remove the compressor to pour the oil out as it would be a lot of work.

Question:

Is there anything foundamentally wrong if I purge it with water to force all the oil mineral out? After I run it with water for a while then I try it with compress air. I can not think of anything that would be damaged if I dry it thoroughly with air. You thought is appreciated.

Thanks

87 300SDL, 83 300D.

 

Do not purge with water! While you may be able to dry most of it fairly rapidly, there is always the possibility of oxidation inside the system that you won't be able to see that could damage the system later.

There is an ester converter that you can add and that's all you need to put in, along with the refrigerant. However, if you've already blown any of the oil out, you need to go ahead and remove the compressor and drain it the rest of the way then refill it.

In addition to changing the drier, you also need to change the expansion valve located behind the trim panel below the passenger side of the dash. You should also check to see if your fan switch on your drier is the hi/lo pressure switch or only the hi pressure switch. If it's only the hi pressure switch you might want to consider putting on the hi/lo pressure switch.

If your system wasn't working at all before you disconnected the drier, don't forget to pull the shrader valve on the low side and pour in the dye then charge with one can of refrigerant to check for leaks. Leaks are common at the front condenser mounts. There's some great red sealant/dye/lubricant in a can that you can get from most auto parts stores for about $10., but unfortunately it won't show you the smaller leaks that the yellow dye will.

 

Converting to R134a will cost you money, give you headaches and cause poor system performance. Best option is to use an R12 replacement refrigerant such as Autofrost or Enviro-Air. These are 100% compatible with R12 systems (and oils) and don't require all of the labor intensive hardware and o-ring / gasket changes. Trust me, this is the best way to go.

 

I don't know FI. Last place I checked, R-12 was $70/lb. I also don't know about 'aren't up to par' or 'poor system performance'. I checked with my local Benz dealer and they've been converting the cars for over 15 years without any problems. My car was ice cold all summer long after the conversion.

I started a thread about this before I converted my own car but didn't get a whole lot of takers for discussion, especially anyone with personal experience doing this themselves, good or bad. I got Drrty240d's comments, but none of those are substantiated with any evidence.

 

My recommendation is based on years of expert experienceas the easiest, least expensive workable solution.Not sure howI could provide evidence of this type of thingvia this discussion forum. Good grief.

Hey, everyone can go to Wal-Mart and buy an Interdynamics134a retrofit kit for all I care. If you think R12 is expensive start pricing new compressors.

 

I have not done anything yet as the recommendations are all over the map, from friends and this forum. I cannot buy R12 as a DIY mechanics and it is expensive, as per cycleboy said, it is around $70/lb. R134a is around $5-$7/lb. That is a lot of savings even I have to recharge it once every 6 months.

The problem is the compressor. The life of the compressor may be shortened if I do not purge most, if not all, of the old mineral oil out and replace it with ester or pag oil. My car is 21 years old and the compressor is not a new baby anyway. That means the compressor may die of natural cause anyway with or without this conversion.

I once converted a Volvo 240DL with an Interdynamics kit and it worked fine for 3 years before I sold the car. I just charged it with the oil from the kit then fill it with R134a. It works fine except it is not as cold as I like it to be. The compressor held up for all 3 years. But at $40 and no hassle, I really cannot complain. I want to do a better job this time around but opening up the compressor is the last thing I want to do.

Can anyone recommend a way to purge the old mineral oil out without removing the compressor from the car?

87 300SDL and 83 300D