Some possible points of leakage are:
-Oil pan gasket
-crankshaft seal
-timing cover gasket
-valve cover gasket
-intake manifold gasket
The best method for narrowing down the leak is to degrease the engine (use a spray degreaser, scrub the crud & rinse) and then keep an eye out for fresh oil marks. Follow those marks to their origin and you'll locate the leak.
they leak oil from the oil pump on the front of the engine
because it may have a leak so yeah a small leak
An oil leak is always going to be out of the engine as the engine contains oil and the car does not. I think you are saying you are loosing oil with no apparent leak. If that is the case the engine is burning oil and that is why you see no leaks.
An oil leak can be from many different places. They include the valve cover, oil pan, front and rear main seals, and oil pressure sending unit.
engine oil leak
If you have an engine oil leak on your 2002 Peugeot 206 1.4, you can use an oil stop-leak product to fix it.
If come from the front left corner of engine then most likely headgasket. (Main oil gallery is on this corner).
If oil is leaking from the riverside of a 1998 Honda Accord the vehicle may be experiencing a front seal leak. The main front seal is located on the crankshaft of the engine.
If the oil is leaking from the front seal you will need to remove the oil pan and replace both the front and rear seals and the rail gaskets.
There are a number of places an Oil Leak can occur take your pick.
Smoke: A engine oil or tranny fluid or lower steering fluid LEAK. Steam: A water leak.
Did you check the oil pump, and oil lines at the front of the engine? Start at the front, because what you're seeing with it going from front to rear could possibly just be blowback from the engine fan.