Milky white residue on the bottom of the oil cap is more commonly the result of excessive short-trip driving where the oil does not get hot enough for the condensation to vaporize and be pulled out through the PCV valve, but white smoke from the tail pipe usually is the definitive clue to a leaking head gasket. Darn the bad luck!
There is two tests you can do to confirm this before you tear the engine apart. One is a chemical test at the radiator. Air is drawn through a glass cylinder with two chambers partially-filled with a special dark blue liquid, while the engine is running. If combustion gases are sneaking into the cooling system, the liquid will turn bright yellow. You can borrow this tester from an auto parts store that rents or borrows tools, but they will make you buy your own bottle of liquid. That is because it is rendered ineffective if it freezes or if it becomes contaminated with antifreeze. They do not want to risk borrowing it to you with contaminated fluid. That is why they made the last person buy their own bottle of fluid.
You can also add a small bottle of dark purple dye to the coolant, then check a day or two later with a black light. The dye will show up as a bright yellow stain that you can follow back to the source. If the cylinder head gasket is leaking, you will find the dye inside the tail pipe. Auto parts stores will have the correct dye for the fluid being tested, and those that rent or borrow tools should have a black light.
For the record, the Shadow and Sundance were some of my favorite cars. They are easy to work on, and are as tough as little ostrich eggs. A friend's girlfriend was driving his Shadow, and pulled into traffic where she was hit in the driver's door by a full-size Monte Carlo going thirty five mph. The impact never made it to the interior door panel thanks to a steel beam inside the door. These cars were way tougher than the plastic Neons that replaced it.
Wednesday, June 20th, 2018 AT 8:16 PM