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· Registered
10 Posts
Discussion Starter · #1 · (Edited)
Hi all,

Having some blue smoke and acceleration hesitation problems with my 550i N62TU. I expect the valve stem seals but am not 100% sure. I did some extensive diagnosis but need your help with this. Maybe things are interrelated or I have serveral issues. This is what I have done so far:

--- Vehicle ---
BMW E60 550i Euro
Model NW51
Engine N62TU
Gearbox ZF6HP26
Mileage: 175000km / 110000mls

--- Software state ---
GKE195 Gearbox ZUSB = 7592144 (latest?)
EK9286 DME ZUSB = 7593395

--- Symptoms ---
hesitation on low acceleration (1000-2000 rpm)
blue smoke when revving engine after 30+ seconds of idling with warm engine
oil in intake manifold
there are coming noticeably blow by gasses out of the valve covers when the CVV hoses are removed (as to be expected I guess)
sound (engine I guess) changes a bit after a long drive (2 hours+). Only noticeable when driving slow (<30 km/h). Vanos?
low engine torque at low RPM's (550-3000), but maybe that is just my perception
engine idling quite rough; cylinder 6 roughness value between 2.00 and 3.10
revving engine from idling not very smooth (also some minor hesitation)
drive train juddering during very low acceleration when the engine is cold (not sure if this is relevant)
slight drive train vibration during acceleration and coasting around 100-120 km/h
several small engine oil and coolant leaks
old coolant looks dark/greyish
no fault codes

-- Relevant checks/repairs ---
new crankcase ventilation valves (hoses are all clean, except some oil)
no vacuum leaks found with smoke test (exhaust not tested)
both engine oil dip stick tube and filler cap have suction
catalytic converters not clogged
fuel pressure during idling: 3.2 bar (nominal value is 3.5 bar)
compression on all cylinders ok
no DISA valve/sleeve movement when cycling ignition (according to the BMW documentation they should move. Can anyone confirm?)
intake manifold under pressure around 50 mbar (as it should be)
fuel trim see picture (+0.5 for additive is this percentage??? of ms?)
fuel system cleaner added (no influence noticed)
driving under high load (caravan in mountains) for two tanks (Shell V-power 100) also no influence noticed
new air intake filter
new engine oil+filter; Castrol Edge Titanium 0W-30 (BMW LL-04)
new spark plugs
coils swapped around cylinders
coolant changed
new battery


· Registered
10 Posts
Discussion Starter · #3 ·
Thanks for your reply Dolfan. I did read a lot the last couple of months. And was hoping I only had a CCV problem. After all the checks/repairs mentioned above I was/am suspecting the valve stem seals also. Strange thing is however that oil consumption is not abnormal (do not have an excessive oil leak either, only small ones) and that the fumes that are coming out of the valve covers (after removing the CCV hoses) do not contain oil, or at least not noticable when putting my hand with a white piece of paper in front of it. Can it be possible that the oil is coming from the intake valves and then straight to the intake manifold? I guess that would be quite unlikely.

Secondly could a valve stem leak leakage cause the hesitation during low acceleration, the rough ideling and the positive additive mixture values? Or are these symptoms totally unrelated? What would be the best way to check this?

This is a picture of the oil in the intake by the way:


· Registered
10 Posts
Discussion Starter · #5 · (Edited)
The additive mixture values are around 0.5-1.0. But I do not know in which units this is given. Is it percentage or milliseconds? According to the usual BMW way of representing mixture values additive should be in ms and multiplicative should be in percentages. But INPA gives percentages for additive. See the image in my first post... This is rather strange don't you think? I do not get any error code. I have read somewhere that the mixture values would need to get very large to trigger a fault code.

· Registered
10 Posts
Discussion Starter · #11 ·
Hello A B,

There is a lot suction on the filler cap and dip stick. Under pressure is around 40-50 mbar in the intake when idling or under low acceleration. Under pressure goes away completely when accelerating harder (all according to INPA readings, sensor could be faulty of course). This is normal I assume since the throttle valve should open more in that case and let the valvetronic do the 'throttling' work. Maybe this explains why the engine is blowing out more blue smoke during idling?

I have to say that the idling behaviour does not differ much when I pull the dip stick or filler cap. One would expect rougher idling due to the added unmetered air, but I do not notice much of a difference.

I have smoked the crankcase/intake system with a smoke tester and found no leaks. Although there can be a small/difficult one to spot.

CCV tubes are in good shape, as are the o-ring seals. No cracks.

Why would disconnecting the Vanos solenoids help is this? This is a simple check and definitely worth a try. But I want to know what and why I am doing. Can you elaborate more on this?

Read your threads on several forums about the Seafoam, unfortunately we do not have access to that in the Netherlands due to import restrictions of chemicals. At least no one took the effort to make it happen.


· Registered
10 Posts
Discussion Starter · #14 ·
Thanks for that info AB Able Truck. I have not tested disconnecting valvetronic because of the increased (and unintended) increase of intake manifold underpressure. First I try everyting I can before trying this.

I have set the minimal valvetronic lift to 0.8mm and increased the idling RPM to 600 (was 550). Idling is better (vibrations wise) and also the smoke seems to be less. Any clue why this is the case? Maybe it is just coincidence or related to enviromental conditions.

Any had some luck on this issue with flashing new DME software?

· Registered
10 Posts
Discussion Starter · #16 ·
Ok, but I meant the smoke. Why is the smoke less with increased valve lift? Only reason I can think of is that the movement of the intake valves is lager and therefore the seal works better somehow. Other than that I see no relation.
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