I have several cars that have factory cruise and for many years the only problem is that the rubber diaphram gets a small hole or tear in it due to being old and getting dried out from the underhood heat. I have successfully repaired seveal of these diaphrams You need to disassemble the servo with a 5/16 nutdriver and carefully remove the diaphram and the sring inside the case hold it up to a strong light and stretch the rubber carefully you will be able to see light through the tear as long as it is not under the paper washer under the metal pull cnter spindle. clean it well with acetone or thinner and buff the area with a stitch buffer then clean again and use a tube repair kit with the proper sized patch and rubber cement. let it dry then wipe the rubber parts down with armourall or a rubber lubricant not on the sealing lip though and use a little silicone sealer to secure the diaphram to the cruise case or it may leak. This has worked for me many times If the diaphram is extemely damaged or torn this will not work and you will need to get a donor diaphram. Good Luck