How did your freind do the conversion?
Did he flush the system and replace the reciever/dryer?
Did he change the oil?
Go here for information on sytem flushing
How long was the sytem inop?
Did the sytem lose all the freon and have a zero pressure, which will allow contaiminents to enter the system.
After the leak allowed you to lose all the freon your system operated for an additional 40 miles?
Sound like you have a blockage in the system.
Without AC guage readings it is hard to figure what is wrong with the sytem.
Your conversion to R134, may cost you more in the long run then fixing the leak and refilling with R12.
The 123 Ac does not do well on R134, the condensor is not large enough for the R134 requirements.
Do a search on Ac systems here in the forum. It will answer a lot of questions
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