I have an 85 300D with the orig. A/C system. I was informed that the compressor has a shaft seal leak and might need to be replaced. On the recommendation of the shop, I opted to pump the system up (needed one lb. of freon) and see how long it would last. The system is still cooling after two months, but not too well. What other problems should I be aware of? I was quoted $820 for a new r4 compressor, new receiver/drier, and a complete system flush and refill. This was from an independent A/C shop that has been in business for 40 yrs. My regular mechanic quoted over $1000 for the same work. Any ideas, suggestions? Should I convert to R134? Thanks