I'm going on your observation of the oil on the timing belt. In that area it's going to get blown around so the source will be hard to pinpoint, especially when everything in the area is wet. You might be able to get an idea by looking for a spray pattern around the crankshaft snout / vibration damper. There will often be streaks of oil shooting straight out and away from the crankshaft. If those are relatively dried and have dirt or mud on them, more likely the oil ran down there from someplace else and got whipped around. If it's coming from the crankshaft seal those streaks will be more wet and shiny and you'll typically see fatter streaks going down than to the sides and up. You may even see a little oil running down from the seal right after stopping the engine. That sounds easy to describe but really it is what experienced mechanics observe without thinking about it that gives them the gut feeling that leads them to the solution faster than for do-it-yourselfers.
You can run an engine with the timing covers removed. I would suggest using a degreaser chemical in a spray can to clean as much as possible, then watch while a helper starts the engine. This is assuming it's a pretty fast leak. Don't overlook a loose oil filter or a double-gasketed one. That's where the old gasket sticks to the engine and you don't catch it before installing the new oil filter. We've all done that at some point in our careers.
If you can discount wind from driving and from rotating engine parts, look for the highest point you find oil since it only runs down. If this is a real slow leak you can add a small bottle of dark purple dye to the oil, then search a little while after driving with a black light. Many auto parts stores can sell you the dye and may have a light to borrow or rent. The dye will show up as a bright yellow stain that you can follow back to the source.
For a little faster leak you may also have luck with a "smoke machine". That allows you to inject a white non-toxic smoke under two pounds of pressure, typically into the dipstick tube, then you watch for where it sneaks out. That won't work for leaks that require the oil to be under normal pressure of 30 to 40 pounds or more. A student found six leaks on my really high-mileage '88 Grand Caravan before finally finding a pinhole rusted through the oil pan with a smoke machine. I don't know if auto parts stores rent those but it's worth asking. All shops have them now because without one, it can be impossible to trace tiny vacuum leaks in emissions systems.
You also have a balance shaft driven by the timing belt. That will have a seal too that can leak. Be aware that your engine is an "interference" engine. That means if the timing belt is off by just a few teeth and you rotate the crankshaft, open valves can be hit and bent by the pistons. Be vary careful if you have to remove the timing belt to replace a seal or other part. Double-check the alignment marks when you put it back together, then rotate the crankshaft at least two complete revolutions by hand to check for binding. Don't force it if it locks up. Instead, go backward, then recheck the marks.
Tuesday, September 4th, 2012 AT 4:04 AM