The rubber parts (bumper fillers, grommets, hoses) on this car were hard as a piece of granite from neglect over the years. Five years ago when my son and I were restoring his Mustang I dropped some of the rubber parts in the parts washer for cleaning but forgot about them for a while. About thirty days or so later when I went back to the task of cleaning the parts were soft as new rubber and wiped clean with a cloth.
Since that time I have used that product for about a thirty day soaked and returned similar results. The product that I used is Harbor Freights water base parts cleaner. I mix the solution 50/50 with water in a small plastic container, throw the parts in and forget about them for a time.
Below are some pictures of the reconditioned parts and the solution. As you can see they are now soft and pliable whereas before they were so hard I thought they would crack. One note of caution though if you soak the color coded headlight vacuum lines the striping will separate from the hose, a shorter soak time seems to prevent that from reoccurring.
