Jorrell is right on the money about flushing the lines and you do need to go both ways on the removal. If you have not replaced the four accessory bushings on the compressor, now is going to be a really good time to do it.

Did this last year on my 86 model give it a 4 on difficulty, 5 on time but I am slow and that is not going to change. Am impressed with performance of the new compressor PAG 40 vs the Ester conversion of three years or so back.

The replacement was a donor R12 compressor from a 90 model that was hit from behind down at the PUP by the way. To flush out the compressor you just need to do to pour PAG 40 oil into both the low and high side holes on the back of the compressor, then pour it out. Stand the compressor up over a container for couple of hours and let it drain well. Then put some more oil in the low side and pointing the compressor away from you (and everything else) manually spin the clutch assembly for a couple of minutes at least. Stand on end and drain one more time and it should be clean and good to go.

You may already be planning this, but if not replace the dryer.

The best way to flush the lines is to pull the dryer lines off, disconnect your compressor lines and remove the compressor. Then go inside the car and open the system at the expansion valve or variable orifice. That will allow you to clean out all the lines and your evaporator and condenser coils. Use the two lines inside the car as the starting point for cleaning and blowing out the lines. That will prevent the flush and stuff inside the lines from coming out inside the car interior. The high pressure line going to the dryer is the only other line you need to clean out. You will find that there is still old oil and gunk up in those lines when they are flushed. You can get a can of cleaner at a local parts house that you spray up in the lines. Then blow the lines out well with compressed air to get all the cleaner and gunk out of the lines. Aim your lines into a container and be aware that oil, solvent, and debris will be coming out of the lines at the pressure of the cleaner or air being used, so please be safe and do this in a well vented area with everyone and everything out of the way (highly recommend safety glasses and a good filter mask.

This will also give you a chance to replace all the o rings and if you are so inclined replace your expansion valve or orifice (you want to replace it). Both will clog up over time and replacing them now will save you time and another trip into the system possibly in the very near future. On my 86 245DL the expansion valve and dryer fittings used the same size diameter o-ring, may be different for other years. Both the dryer and the expansion valve were less than $20 each.

Be sure to add PAG to the dryer before installing it, the instructions on the dryer should tell you how much (my last one was 1 oz). The dryer should be the last thing installed before you close up the system. That is to prevent the desiccant inside the dryer from absorbing moisture from the air. Subtract that amount of oil from what you add to the compressor. Too much oil just like an overcharge of coolant will reduce the efficiency of the system. Some articles suggest (and I did this on my wifey’s non Volvo compressor replacement this winter), that you actually put in two less ounces of oil in the compressor and use a can of oil/R134 charge (2 oz of oil) as your first can doing the fill. The logic there is that you spread oil through the system before adding more coolant. Either way, you will want to jumper the low pressure switch and let the system run with the compressor engaged to allow oil to get moving before starting the fill.

Use the 80% rule doing the fill of the system when it comes to adding coolant. So it should take just a bit over 3 cans of 12 oz R134 to fill the system.

You can get a “loaner tool” evacuation system from one of the national auto part chains if you want to pull a vacuum. The reason to pull the system down is to check for leaks before adding new coolant. Personally have had great success doing the “redneck vacuum” which is to jumper the low pressure switch, start the car up, and after letting the compressor growl for a minute or so and then start filling the system slowly. R134 does not have the same issues with moisture vapor that R12 did by the way. That is why you can get away with not doing a vacuum. The pro is that the vacuum will find leaks, and the con is you have to have access to a pump when the time comes.

Final tip on doing the fill is to keep your pressure on the low side below 40 to 50 psi during the fill. That is to prevent a pressure spike from damaging the internal compressor seals, just keep the fill pressure low and slow for best results. The best system pressure for my 86 seems to be 35 to 37 psi on the low side a high side pressure of less than 220 psi on a nice warm Gulf Coast day of say low 90’s. High side pressures may vary based on humidity, outside air temperature, moon phase, and the general condition of your compressor seals. Take it out for a drive and if cooling well at highway speeds is my method of choice for a stock 240 system. There are other mods that also can help if you are still wanting better performance at slower speeds. Post back later after getting the system working if this leaves you wanting more.

Good Luck and get your cool back on,

Paul