In this entry, I will describe quite a typical situation. Not only in connection with VANOS. But, as the diagnostics have indicated, there is a problem with the positions of the camshafts; the topic of this entry will be exactly regarding this hub.
here, how the VANOS menu looks:

As we see, the reference positions of both camshafts are strongly shifted from the ideal (0) position. Even more – they are far in the red sector. Without a doubt, the appropriate error messages are recorded in the error message memory of DME.
The problem is clear; it has to be solved. In this case, the vehicle owner reported that the repair works of this hub were performed recently. It was not a surprise to me because the camshafts do not regulate co incorrectly in the BMW AG factory.
The owner of the vehicle got in touch with the service specialist, who performed the repair works. As it usually happens in such situations, a typical “circle dance” started. The repair specialist did not admit his failure. He mentioned several possible causes of the problem – starting with the mechanical damages of the VANOS hub itself and coming to “the chain of the engine is stretched.” Exactly this co-called “circle dance” is the unifying element of many unprofessional repairs!
Let’s see the possible causes of the problem.
a. Stretched chain of the engine. No, this will not be the real cause. To shift the position of the camshafts so significantly, the chain has to be stretched for at least 2 .. 3cm. It is NOT possible.
b. The defect of VANOS mechanisms. For both camshafts? In addition, a logical question arises – what could break for BOTH mechanisms at the same time? They repaired it a short time ago! Gather information regarding several thousands of these engines; none of them has identified mechanical problems of VANOS. But for this current engine – was (additional, for both hubs!), then it was repaired, and now they appeared again? Illogical!
c. Leaking valves. In theory, leaking valves can change the reference positions of the camshafts, but in this case, the defect would not be stable. To check the leaking of the valve as the cause of the problem, I suggested the car owner perform the test described below.
Test for checking the VANOS reference positions.
a. connect INPA, open VANOS menu ../F5/F4
b. start the engine, observe reference positions of both camshafts;
c. stop the engine, repeat the test several times, compare the results.
If the positions of both camshafts are stable for the first seconds after the start and the differences of the test results are insignificant (tenths of the grade), we can dismiss the problem of leaking valves. Leaking injectors do not stand out with the stability of the leakage; in addition, the leaking is strongly impacted by the oil pressure (which also is not very stable at the moment of the start).
This time, the test results were the following:

As we see, the results are very similar. They are not completely identical, which means that the customer really has performed the test (not, for example, sent 5 copies of the same image). Unfortunately, the service specialist has failed this time.
My suggestions:
a. The VANOS hub of N series engines is a very safe and long-life hub. I haven’t seen any N series engine whose VANOS hub would fail mechanically. Even if there is strong wear and increased oil consumption in this hub, it does not give fundamental problems because the electrically manageable oil pumps have high flowrate and reserve of the pressure;
b. don’t trust the replacement of the chain tensioner and guide rail, who doesn’t have the OEM toolset for fixing of the camshafts and the crankshaft, and who is not familiar with INPA, at least in such a level when he could check the result of his own work;
c. keep away from a service specialist who does not start with the analysis of the live data (reference positions, PWM jittering of the valve management) when he sees the error messages regarding VANOS but is ready to screw something immediately. Good, if the service specialist offers to replace some valve, but it is completely inadequate if he is ready to dismantle the VANOS mechanisms, to “repair” them;
d. VANOS valves can not be cleaned. The valves of N43/N53 series engines are sealed; even cleaning with ultrasound + electrical + mechanical cycling (operation) does not give a stable result. If the service specialist offers to “clean” the valves, blowing them with air or, for example, dipping in the petrol – be sure that the knowledge of this “specialist” is at zero levels.
Unfortunately, the cases when the service specialists “repair” the VANOS valves (without any reason) but actually don’t even know how to fix the correct position of the camshafts are not rare. The customer pays for a “solving” of a nonexistent problem, then – fights the consequences. The name of this entry, “what to blame,” actually can be replaced with “who to blame”…