I am publishing a series of articles regarding VANOS problems and this current specifically – it affects the major part of the BMW petrol engines. Even the most amount of entirely new cars (including the ones still on warranty) have minor or more significant problems with this hub and this specific defect (described below and in following chapters). Unfortunately (or luckily), most users and repair specialists don’t even suspect it.
This series of articles won’t be any replacement for VANOS gears and mechanisms. If you support the repair kits – these articles are not for you. The reason is simple – for N series engines, I never had problems with the mechanism’s performance (except in cases when after unjustified “repair”, they are incorrectly assembled). In none of the issues, when I received information that the mechanisms were replaced during the repair of VANOS, I did not get confirmation of the objective necessity of such repair. The typical answer to my question, why the mechanism was replaced, the service specialist answered: ”well, there were error messages regarding VANOS…” When I ask about live data or PWM values of the valves and other data, not even once do I get any information. While I haven’t got contrary information, I believe that the VANOS mechanisms of N (and B) series engines are very long-life, and their replacement for sure is not the thing with which to start the repair of VANOS.
This series of articles won’t be stories regarding simple defects, for example, breach of the solenoid winding. Such defects are identified with the error messages in the DME error message memory; their identification doesn’t ask for specific knowledge. In the articles, I will talk about performance things. So – I will describe situations when most probably there are (not yet/at all) error messages in the DME error message memory and the defect is “hiding”.

Instead of an introduction (ahead of the build-up nuances), basic things in Q/A format:
Q. Which engines are “suffering” from these VANOS performance problems?
A. All N and B series petrol engines, because they all are equipped with VANOS (both inlet and outlet camshafts).
Q. What is the reason for these problems?
A. Unequivocally – long oil change intervals. Even one or two intervals of 30 .. 35.000 km oil use can be (and often are) the cause of these VANOS problems.
Q. How many cars are facing VANOS problems?
A. Very roughly – at least 4 of 5 cars to 100.000 km already have (hidden) problems with this hub. Yes, it is possible that the symptoms still can not be noticed (or – the existing issues are “addressed” to other hubs) and/or no error messages have yet been recorded in the DME. Still, problems can very well be seen during diagnostics.
Q. Which one of the VANOS hubs (inlet/outlet) is more subjected to the problems?
A. In 90%, the outlet VANOS hub is the first to manifest the problem.
Q. How to avoid VANOS problems?
A. Regular oil changes (not less than every 10.000 km), dynamic driving (it will help clear the VANOS valves).
Q. Why should these problems be solved ASAP?
A. All mechanic Valvetronic parts of the engines are wearing out much faster if the engine has VANOS performance problems – starting with its motors, bearings; worm gear; eccentric shaft; and roller drag lever. The electronic throttle and CO catalytic converters will also wear out much faster. If the wear of these spare parts exceeds the norm, the repair will be expensive.

And now more detailed regarding problem itself and its manifestations
The most popular VANOS problem (if we discard, for example, damages of some particular hub) can be divided into 3 phases:
a. partially clogged valve. DME (and the solenoid of the valve) has to use additional power to maintain the required position of the camshaft. PWM jitter of the solenoid increases significantly;
b. the valve continues to clog. DME is not able anymore to maintain the position of the camshaft. The short-term difference in the camshaft position increases more and more – the jitter of the shaft position increases;
c. the valve is clogged so significantly that it is not possible to maintain the position of the camshaft anymore. The actual camshaft position is more and more different from the required one. VANOS hub fails permanently.

More details regarding symptoms in each of the previously mentioned stages:
a. no symptoms are observed by the user. The engine continues to work correctly (if it has no other problems). It is possible that increased unevenness of the engine performance can be observed during “non-standard” processes (for example, during desulfation sessions of N43/N53 series engines and warming-up of a cold engine for B series engines). Still, it is typically “blamed” on other problems – injectors; fuel; ignition system (spark plugs; injectors), etc. No error messages were recorded in the DME error message memory. Positions of the camshafts (checking them on INPA/ISTA live data) – stable. Short-term shivering can be felt during transition processes (for example, swiftly changing required torque, switching gears), but usually, as the culprits, others/previously mentioned hubs are marked. The problem is seen during advanced diagnostics;
b. following symptoms appear: “more restless” idle (as if “partial” misfires can be felt); on the go, the car moves as if with pushes. Particularly pronounced shivering was observed for N43/N53 series engines during the desulfation process. For B series engines, shivering in idle starts to appear during the first minute after starting the cold/cool engine. But these symptoms are often “written off” to injectors; ignition problems; fuel system (its pressure jitter), and others. The position of the camshafts (typically – for the outlet shaft) shivers in the problematic driving conditions. This jitter reaches +/-5 .. 10 degrees or even more. The problems start to be visible during “standard” diagnostics when checking live data. There are still no error messages in the DME error message memory;
c. in the DME error message memory, (finally) the error messages regarding the inability of VANOS to reach/maintain the required position appear. Typical requirements for recording the error message: differences between the required and actual position of the camshaft – at least 20 degrees for 1 .. 3 seconds. The VANOS hub is disabled. Power of the engine – reduced (for example, the torque, available for B58: from 450+ Nm to 360 Nm). Responsivity to the accelerator pedal – slowed down. The engine becomes “clumsy”; it has no “sharpness”; no power. Deleting the error messages and starting a new driving session, DME tries to restore the performance of VANOS, but now already in live data can be seen that the position of the camshaft is precarious. In problematic conditions, the performance of VANOS is disabled repeatedly.

The reason for all these problems is quite simple – clogging of the regulating valve. The cause – is rare oil changes. It is enough even with one/two (recommended by BMW) 30 .. 35.000 oil change intervals (even driving with correct driving profile – with a significant average speed) for the exhaust VANOS hub would suffer intensely.

Why exactly is the exhaust VANOS hub?
My experience shows that precisely the exhaust VANOS is the one to suffer. Driving dynamically, the inlet VANOS valve can serve for a long time (200 .. 300.000 km and more), but the exhaust VANOS often suffers before reaching 100.000 km.
My first thought was – maybe the oiling channels in the engine block are created in a way that the exhaust valve (its strainer) partially serves as a filter? Or, perhaps, the oil flow rate is more significant for the inlet VANOS valve, and it can “flush” dirt better? I don’t have images of all oil channels of all engine blocks, but those I have to confirm – no, both VANOS valves are supplied via separate oiling channels from the joint oil rail.
Next idea: Is it possible that the too-narrow VANOS work range is to blame? For N and B series engines, the typical adjustment range of inlet/outlet VANOS is 70/60 degrees. In real driving conditions, the inlet is related to the range of at least 65 degrees, but the outlet – is only 35 .. 40 degrees. Maybe due to this, the exhaust VANOS works only partially and is not cleaning? No, the analysis of PWM data shows that the inlet valve doesn’t have a much better situation.
The last version exhaust VANOS valve is not cleaned because most part of the time, it is practically closed (the oil, which gets inside, is not flushed out). Instead, the inlet VANOS is actively working all the time (if you drive at least close to the appropriate performance of the BMW). The outlet VANOS is actively used when the CO catalytic converters are warmed up and for N43/N53 series engines – during the desulfation of the NOx catalytic converter.
Unfortunately, it looks like the only way for us/users of the BMW is no other option to prolong the work-life of the VANOS than changing the oil in the engine often.

In short, about available data
INPA. The most comprehensive amount of data is offered by MSD80 DME. For this DME, we can see the reference of the camshafts and required and detected positions.

In the test block, the PWM of the valves can be seen.

For older Simens DME, the PWM data of the valves are not available. Also, Bosch DME typically has no PWM data available.
ISTA typically gives information only regarding the detected position of the camshafts.

In ISTA test blocks, the tested shaft’s typically required and detected position is displayed; a test has to be performed for each shaft separately. In the image – VANOS test of BX8 engine.