[HO455]

Any ideas on the age or mileage on the motor? On high mileage motors any gasket may be leaking. Cheap gaskets will fall before quality gaskets will. And any gasket can fail if improperly installed.

Common points that leak but don't cause other problems (Like a leaking head gasket may)
The front and rear intake manifold gaskets.
Rear main seal.
Oil pan gasket.
Front main seal.
Fuel pump.
Valve covers. This can be from bent or deformed covers as well gasket failure.
There are more but these are the most common ones I've seen over the years.

Replacing the PVC valve and hose can help as a collapsed hose or stuck valve can allow pressure to build in the crankcase.

Generally if I have a really dirty engine I will take it to the DIY car wash and use their engine wash and the high pressure spray. Just stay clear of the upper part of the engine with the spraying. And wear some safety glasses.

Old plug wires are susceptible to grounding out when wet so it's best to avoid the car wash if your plug wires are old or questionable. Taking some WD40 to spray the plug wires down after cleaning the engine is a good idea.

You didn't mention what style of transmission. The front seal on automatics can leak as well as the seal around their dipstick tube adding to the mess.

There are dyes you can add to your oil that in combination with a black light can help locate leaks. Some professionals swear by them as they make it easier to find the leak when clean oil is leaking.

Good luck on your search.