Thread by Cornblatt was great. My overflow tube had shrunk by two inches. Overflow tube was full of crud, so needed to blow it out to clear. So far, so good.

Purchased some 5/8" clear plastic tubing, which fit the overflow tube perfectly.

Unfortunately, plumbing suppliers to not stock 5/8" barb couplings, so used 1/2" barb and two hose clamps to secure the assembly.

Now for the smell. Years of overflow had softened the sound deadening material over the rear passenger wheelwell in trunk. Used a stiff putty knife to pry up and remove all material in this area. Wiped area clean with rags. Then used spray on brake parts cleaner which dissolved the diesel/sound material residue. Wiped that up with rags. Brake cleaner evaporated quickly, but some smell remained.

Used 100% white vinegar to remove residual smell on metal. The trunk thin side and floor carpet had also soaked up some diesel. Saturated the carpet with vinegar, and blotted with thick cloths.

No leak, no smell. Mission accomplished