The reason, IF, you say there are no bubbles showing in the sight glass, is because the auxiliary fan in front of the radiator is not functioning and is needed at slower operating speeds. Check to see if it operates, if not, then:

This can happen due to a blown fuse, a defective AC relay, engine temperature sensor or a bad pressure switch on top of your AC drier. To check the drier switch pull the two wires from the pigtails on the sensor on the top/side of the drier and short them out, hence bypassing the switch. If the fan works with the engine running, the switch is bad and needs replacing. Use a lower temp switch which is RED and not the higher temp switch which is Green. This allows the fan to come on sooner. The switch
removal will allow all the freon to escape (unlike newer cars) and will have to be recharged.

If the fan doesn't run look for a bad fuse and check your AC relay
to repair the fan operation.

Good luck with your AC fix.

TobiasMB
3 MBs

PS. The AC freon leakage happens through the porosity of the hose, due ti its construction.