Some things to consider.
The oil in your open system has absorbed water.
The reciever/dryer in your system is now full of water too, and MUST be replaced.
I've had good success flushing out old oil with "white gas." This is what you buy in 1 gallon conatiners and burn in Colman lamps. (I have not seen it in awhile.) I would use a funnel, and choose a suction hose. Remove the hose at a fitting, gently flex it up so you can pour in the white gas, you only need to fill the hose a little. Then take compressed air with a blower that has a rubber pointed nozzle on it. Plug the hose fitting, and gently use the compressed air to blow the white gas through the system.
Oh, LOL, watch out as the other side of the fitting is going to spray oil and white gas out! Wear goggles and gloves. A long sleave shirt is a good idea too.
Flush it a few times, and you MIGHT remove that crap you put into the system. The oils used for R134a and R12 are NOT compatible. Once the seals have been exposed to R134a, I've been told it's not wise to return to R12 either. The reciever/dryer has to be changed in any course as it's a filter for the oil, contains some as well, and the desicant pack absorbs free water in the sytem.
It has been discussed before, but the R134a is not as effective as R12 in this system build/sized for R12. (R134a based systems are designed larger because it's not as effective, thus you need more of it, and a larger condensor, lines and evap core to make it cool your car correctly.) This may only matter on days when it's 105f with bright sun light. Adding tint to the windows, and use on less hot days might be fine with the R134a.
Here's what I'd do. Get the white gas, and flush your lines. (I don't need to tell you this stuff is flamable right? Even a lit cig, or open flame ANYWHERE near this will burn down your car, and you likely since your going to get sprayed with some oil and white gas residue.)
Flush the system till no more oil comes out. (Might take about 5 times, possibly more since you added all that oil shit to your system.)
Replace the reciever/dryer after you flush the sytem.
Go to an AC shop, and have them pull down a vac on the system to 30mhg, and leave it there for a few HOURS. (Not just an hour, but 1/2 the day if they are not too busy. This is generally the case if your using R12 as not many do anymore, and the R12 equipment is sitting around idle most of the time.) What's going to happen with you pulling vac on the system for so long is the water and oil that is still trapped in your system should be removed. (Water mostly, but some oil will be sucked out too.) In a pure vacume, the water turns to ice, and then vapor and is removed.
If your system holds a vac, it's sealed up and has no leaks.
Charge with R134a since you have already put that in, and contaminated the seals with it. (I'm just hoping you did not turn the remaining R12 type oil into an acid by exposing it to R134a and the water that was in your system. Freon and water equals acid. Wrong types of freon and oil create acids too. and these acids eat your system from the inside out. (First to go usually is the expansion valve, the orifice is enlarged by the acid, it let's too much freon through, and you get reduced cooling as a result since the expanding freon is not in the evaporator long enough to fully expand, it ices up your suction pipes to the compressor when this happens.) Basicly, much of your cooling ability is just cooling pipes in the engine bay. Worthless effect.
There were a few questions about reciever/dryers iceing up, or being cold. It totally depends on how it was designed, and which lines the R/D is placed in. If like the Supra system, the R/D is in a high pressure/discharge line, it's going to be hot like the compressed freon is. The reverse is true if the R/D is placed in a low pressure/suction line where the freon has mostly expanded, and now is a froth/gas being sucked back into the compressor to start over again.
Last but not least, is another misconception talked about here. Freon (in R12 or R134a form) is not easy to pump. The compressor oil is easy to pump around however, and it "chases" the freon through the system. (The oil moving around, tends to move the freon around with it. Not the freon moving the oil as stated in this thread.)
Best of luck, but I think you totally screwed up your system with the oil and R134a experiment. (Our systems were designed for R12, and should have R12 in them to be the most effective.)
