Philes’ Forum – Winter 2017


“I changed my oil and now my Check Engine light is on! WTF?”

By Vic Lucariello, Sr.

Hello, bimmerphiles! Here we are commencing the 31st year of Philes’ Forum! Time surely flies, and surely the world, BMWs, and the BMW CCA have changed in the last 30 years. You decide what changes have been for better or worse. Judging by their ever-increasing sales numbers, BMW might be considered to be doing well. However, it is no accident that the newest BMW I own is a 1995 325is, which is not accused of being a less-reliable Lexus. Anyway, this time out I have an important tip for those of you bimmerphiles who change your own oil.

I hope this has never happened to you, or to your shop if you have your oil changed, but it has happened to both DIY bimmerphiles as well as auto-repair shops. A routine oil and filter change results in a newly illuminated “Check Engine” indication and, sometimes in addition, rough running of your Bavarian engineering masterpiece. The problem can occur immediately after the oil change or shortly thereafter. Scanning the DME [BMW-speak for the engine-control computer; anyone know what “DME” stands for?] results in diagnostic trouble codes [DTCs] related to the engine VANOS system.

What is VANOS?, you ask. VANOS is BMW’s term for their variable-valve-timing [VVT] system, which was introduced on U.S.-spec models in the early ‘90s. Other manufacturers have their own versions. The first VANOS were applied to intake camshafts only, while later VANOS control both the intake and exhaust camshafts. Hot-rodders and engine designers have been wrestling with valve timing for more than 100 years. Valve timing, which refers to when the intake and exhaust valves open and close with respect to piston position, determines the “character” of an engine. For example, closing the intake valve later produces more high-RPM power while closing it earlier produces more low-RPM torque. A VVT system can vary the valve timing with RPM and load to produce an engine with both low-RPM torque and high RPM power with better fuel economy and reduced exhaust emissions. Pretty cool if ya ask me. But of course, there are downsides.

Most VVT systems are hydraulically operated using oil tapped off of the engine’s lubrication system. VANOS is no exception. So any manufacturer’s VVT needs clean oil of the proper viscosity and at the correct pressure. VVT also requires sensors, solenoids and engine-computer software to monitor how well the VVT is functioning. On recent BMWs, the DME not only monitors if the camshafts, and hence the valves, are at their commanded positions but also how quickly they change position when commanded to do so. So you can see how dirty oil, oil of the incorrect viscosity or oil at the wrong pressure can cause VVT malfunctions.

And that [finally] brings us to this month’s topic: How to avoid causing your “Check Engine” light to come on simply by doing an oil and filter change. Beginning with the N52 six-cylinders that appeared in the E60 5-Series more than 10 years ago, one must be very careful, when removing the oil filter, not to break the filter cap/inner-cage assembly such that the filter cage remains in and is discarded with the old oil filter. The cap and cage [see Photo #1, courtesy of Ron Gemeinhardt] come as an assembly, so if the cage breaks off, one must buy the whole thing. My understanding of what happens when the new filter is installed without the cage is that unfiltered oil at a reduced pressure is supplied to the engine and therefore the VANOS. The VANOS solenoids that supply oil to the VANOS system have screens at their inlets and these screens can become obstructed when supplied with unfiltered oil. Low oil pressure just exacerbates the situation.

So how do you minimize the possibility of breaking the cage off the filter cap? Tech worker Doug Feigel suggests that, after unscrewing the filter cap, pull the cap/cage/filter straight up; don’t wiggle it side-to-side or cock it in an attempt to dislodge the filter. Or, as engineer Doug puts it, “Remove the cap/filter/ cage in a linear fashion”. Doug also suggests the following:

  • The new oil filter should come with a new o-ring for the filter cap. Be sure to install this o-ring in the provided groove in the cap, not above the groove flush against the cap shoulder. [Vic adds that the new o-ring should receive a coating of clean engine oil after the o-ring is happily ensconced in its groove.]
  • Don’t over- or under-tighten the oil-filter cap. There is a special 3/8–inch drive cap wrench that you should procure if you are changing BMW oil filters. The 3/8-inch drive allows you to use your torque wrench to tighten properly the filter cap to 25 newton-meters [about 18.5 lb-ft]. [Vic: You have the torque wrench out already for the oil-pan plug, RIGHT?]
Photo #1 – Oil Filter Cap And Cage, courtesy of Ron Gemeinhardt

I would like to thank Doug, Tech worker and Chapter Treasurer Ron Gemeinhardt, and Matt Kimple, Service Manager at BMW of Bridgewater, for consulting with me on this column. Matt provided me with a copy of BMW’s service bulletin pertaining to this problem.

BMW of Bridgewater [formerly Hunterdon BMW and before that Foreign Cars of Hunterdon] is located at 655 Rt. 202/206. 888- 928-4089. Prior to my leaving New Jersey, they were my dealer of choice for more than 30 years. When you are there, say Hi to Matt for me.

That’s all for now, bimmerphiles. See you next time. Anyone wishing to contribute to Philes’ Forum can contact me at I’m interested in tech tips, repair / maintenance questions, repair horror stories, emissionsinspection sagas, product evaluations, etc.

© 2017; V.M. Lucariello, P.E.

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