Oil in the oil pan is not under pressure. The oil gets picked up in the pan, then run through the pump which puts it under pressure and sends it to all the critical places through passages cast into the engine block and cylinder head(s). Once it's done "doing its thing", which is to isolate moving parts from each other, it leaks out of those places at a slow, controlled rate, then it's no longer under pressure. It gets collected in channels and runs back down to the oil pan. Some of that non-pressurized oil also drips or gets sprayed onto other critical parts where oil is necessary but it doesn't have to be under pressure. Camshaft lobes are a good example of that. Some also gets splashed or sprayed onto the cylinder walls to keep the pistons sliding freely. If you remove the oil fill cap while the engine is running, you'll see there's no pressure there either. Well, ... There's not supposed to be, but if there's excessive blowby past the piston rings, you might see a little pressure, but not enough to be concerned with.
Most oil leaks occur from places where the oil isn't under pressure, like valve cover gaskets and oil pan gaskets. Common places for pressurized oil to leak include the oil pressure sending unit, oil filter, and crankshaft front and rear seals.
If the oil leaks fast enough to drip while you're standing there watching it, you should be able to find the source pretty easily. You might have to wash the engine first with an engine degreaser. Most of those products work best when the engine is just warm, but not at full, normal temperature. I use a green product from the Chrysler dealer's parts department but you have to buy it in five-gallon pails. It looks like thick antifreeze. The most important thing is it wont do anything if it's poured onto the engine. It has to be sprayed from a spray or squirt bottle. Auto parts stores will have spray cans of degreaser that also work pretty well.
If you can't narrow down exactly where the oil is leaking from, you might be able to borrow a smoke machine from an auto parts store that rents or borrows tools. Stick the probe into the dip stick tube and seal it with a rag, then smoke away. The white, non-toxic smoke will be under two pounds of pressure. After a minute or two you'll see it sneaking out, but this only works when the leak is at a non-pressurized point. The smoke can't push its way through the oil that's standing in the passages where it's under pressure when the engine is running. Oh, ... This is done with the engine not running.
You can also add a small bottle of dark purple dye to the oil, then search a little while later with a black light. The dye will show up as a bright yellow stain that you can follow back to the source. This works best with real slow leaks, especially if you have something that vaporizes almost as soon as it leaks out. Antifreeze is a good example of a liquid that can leak and be gone before you get a chance to see it. If you use dye, the people at the auto parts stores will ask you what you're using it for, so they give you the right product. As I recall, you can use the same product for transmission fluid and power steering fluid. Engine oil dye is different. AC system dye is too and it has to be injected with special equipment. I don't know that I've ever seen this stuff for brake fluid, but if there is such a product, it is extremely critical that you don't contaminate brake fluid with any type of petroleum product, including their dyes. One drop of any of those lubricants will cause a disaster and a REAL huge repair bill.
Thursday, April 9th, 2015 AT 4:15 PM