There's two ways to find the source of a leak. One is to add a small bottle of dye to the oil, then search with a black light. The dye will show up as a bright yellow stain that you follow back to the source. That doesn't work well though when the leak is as fast as it sounds like because the oil and dye will be everywhere right away.
A better alternative is to use a smoke machine to inject a white non-toxic smoke at 2 psi into the dipstick tube, then watch for where it sneaks out. A student found six leaks on my '88 Grand Caravan that way including a camshaft seal, valve cover gasket, and distributor adapter o-ring. With every repair the leak got worse and appeared to be a leaking rear main seal. After looking closer we found a pinhole rusted in a high point on the oil pan. Fixing each leak caused pressure to build in the crankcase and help push the oil out of that hole faster. You might find a smoke machine at an auto parts store that borrows or rents tools.
Thursday, November 8th, 2012 AT 8:39 AM