n54 boost selenoids: Leak and Resistance Test of a new pair

Just for testing. Here are two new selenoids from Pierburg which is the supplier for these of BMW. Seems to be that the membran (or whatever in the valve is for sealing) can act freely in the selenoid in case it's no voltage attached. Therefore already the gravity.. or a little bit more by shaking.. is enough for a leakage test. In case voltage is attached (+-.. Doesn't matter which polarity) it needs to be open / not sealed.

Some selenoids may fail because of a leakage problem, maybe also a broken membran. Heat could also disturb the movement in the selenoid of the membran. The movement is important because BMW gives am PWM signal to define the vacuum for the wastegates. Means how much vacuum goes to the wastegate to define the turbo pressure. In case the selenoid can't follow the signal because of a not moveable inner part it may create to low boost pressure or to high in case it sticks in the "forward vacuum" position. A sucessfull test like this in ambient temp. isn't a 100% guarantee. Therefore broken selenoids are potencially the reason for some cars which get a failure for to high (or to low) boost pressure.

In case of to low boost check first your vacuum lines. That's the more common rootcause.

In case of to high boost clean your vanos selenoids first and check the boost pressure and temp. signals by a log incl. the wgdc values and verify that the sensors are working with reasonable values. Beside this it can be also a not properly working wastegate due to bad install of the v clamps (e.g. after downpipe intall) or a sticky wastegate movement.