I don't know if the vacuum actuators for the 83 are the same as my 84 300D.

You need to determine what is leaking.

The outside boot is the most repairable. People have used n tip of a rubber or latex glove for that or somewhere in the thread there is Bosch rubber boots.

On mine it was the inside diapered that had developed slit in the corner of it. In the corner a bicycle patch would have been I believe too thick.

I don't know the rubber cement for bicycles tubes would stick a slit back together or not. But one of our members used glue that he used to repair his diving wet suite.

The possibility of repair depends on what you find. So you would need to remove it test it and take it apart and see.

I tested mine by hooking some vacuum hose to one nipple and blowing into the hose with the actuator under water.

The bodies on my 84 are plastic. The older W123 vacuum actuators had metal bodies and there at one time was kits to repair them.

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84 300D, 82 Volvo 244Gl Diesel