Smoking below 50 degrees (Engine)

[M80]

2014 Viano 639.
OM651, 2.1
165K miles.

I've read a couple with similar issue but not read a definitive diagnosis as yet, so in hope.
I noticed yesterday at about ambient -4 on start up after about 3 seconds there is smoke, with a fuel smell.
It starts easily and runs very well.
I drive and when stationary (lights /junctions) there is smoke evident until approx 50 degrees engine temp, then it runs cleanly.

I'm aware that these over fuel when cold, but this seems like excessive overfuel and I wouldn't expect same at such engine temps.



2nd issue possibly related but don't think so.
With a new stat from MB Newcastle.
Still slow to warm up (common for the 651 apparently). It was fast enough to get to the 50 degrees but after 16 miles (6 miles of cruising at 70+) the temp was at 72, by 18 miles (more gentle driving) had dropped to 67 again.
I' m aware that the ECU now controls the stat and design temp is said to be 70 - 100 degrees, but this still seems like a faulty stat, any thoughts.

MB Newcastle say it has a 2year g'tee and to take it to a main dealer for diagnostic. I would expect a bill for £150 for that and a possible free unwanted update to the ECU, so I'm reluctant. Beside I don't see that Star can diagnose a faulty stat, that takes a drive, a flippin' long one in my experience.

Thoughts appreciated.

 

[M80]

I took it for a test drive earlier.
Smokes when cold, when that stops there is evidence a black puff of smoke when pressing the throttle when stationary . When driving there is a whine under power, possible air leak??

Could this be a leaking intake manifold, as these are plastic?

 

[LostKiwi]

How's the turbo? Any movement on the turbine shaft if you take off the boost hose and move the spindle axially and laterally?

 

[bladecrazy]

Have you done a leak off test? i think the inlet manifolds are plastic so thats a possiblity, what colour is the smoke from cold?

 

[M80]

I haven't started intrusive diagnosis yet. I'm hoping to have some reasonable direction before digging in and possibly upsetting things w/o good reason.

I'm not seeing anything untoward on Torque, such as strange temperature readings. The inlet temp (taken from the MAF methinks) follows ambient. Although I would expect it to rise above ambient it hasn't today.
I use that much as it is on my 9" Android HU, so easy to monitor. But it maybe I'm not looking where I should.

I've so far failed to find drawings of the engine sensors on my WIS DVD's. That could allow me to work through eliminating and then concentrating on those appropriate.

 

[ajlsl600]

Get some card block of part of rad .see if car warms up quicker and white smoke stops quicker ,(,fuelling )? If improvement statt ? Sticking open .think benz have turned that into a £100 bit now.!! Does my head in..good luck..

 

[M80]

I agree about the stat. Having the ECU opening the stat as it sees extra power being used seems so unnecessary and an extra complication.
For enough years and models a stat that opens due to temperature of the coolant has been good enough. Even if that has some delay it hasn't caused issue for so many mega mileage cars.
Now we have an ECU that might cause issue to that, and an additional component in the stat to open as the signal tells it to.
It's likely designed to improve emission's, but as the lower temperature consumes more fuel it must fail in the long run.

Anyway turbo seems healthy, then it rained.
Now to remove the PCV.

 

[ajlsl600]

Hope u get sorted.thing is,dont think I have changed more than 2,3 ,statts in.my career yet it seems quite common now ,another step back,for consumer .how does it work ,a step forward just brings another headache and complication.

 

[M80]

Considering the newly developed whine, and black smoke on acceleration I'm thinking boost leak somewhere??

Finding the source of the whine is difficult stationary as I expect that is under turbo boost.

So a bit of reading and a pressure test might serve purpose, but a smoke test might be needed if I can't identify with soapy water??

Does this sound right?

Rigging up a pressure test device may be feasible, but a smoke test isn't something I can think of how to create.
So I'm thinking Indie to diagnose at least, better they just do the job cos I'm out of enthusiasm to be crawling around in the cold and wet. But the ex long isn't something many can get on the ramps, if they would need to.
Ah the joys