Here's a question for the A/C pros/specialists out there. This is on a 1986 300E with the original R12 system:

How can I determine whether the oil in my air conditioning system is at the proper level or not? I replaced the A/C hose assembly, expansion valve and the receiver-drier over the weekend. According to the service CD, I should be replacing 20cc for the hose assembly and 20cc for the receiver drier. However, I wasn't able to drain any more than about 10 drops out of the complete hose/manifold assembly. I haven't tried draining receiver-drier yet, but will try that tonight. And do I just inject the oil into one of the lines or the receiver-drier itself? Or is there one place in the system where the oil tends to collect that can be drained and refilled with a known amount? Is there any danger in overfilling the system?

I want to take the car in tomorrow to have it evacuated and refilled with R12, but I want to make sure there's the right amount of lubricant in it first.

I also noticed a some rust-appearing corrosion inside the condensor pipe where the metal pressure line connects to the LH side of the condensor. Is this anything to worry or do anything about? The rest of the lines appeared clean and corrosion free.

Thanks for any help.

Gary