90 740T smokes

Hi all,

My 90 740 turbo intercooler has begun showing Blue/white smoke when
engine is warm. (the needle is in the middle of temp gauge)
I looked at the dip stick, after a while, and the level didn't
decrease, so the car doesn't consume extra oil, that's my problem.
ALso, I Replaced Turbo 1000 km ago . ( 285 000 km total) Have been
faithful about changing
oil. Compression is excellent all four cylinders ( around 130 psi
each).
Engine never overheated. Impeller turns freely. No unusual noises
when
running. Slight amount of oil or prestone in intlet side of piping.
There is also some oil that is leaking in my intercooler, i removed the

screw under and it gave me around 2-3 ml of black oil. (old oil because
a made a oil change)
Also, my fuel tank decrease rapidly.

So, if someone can help me or have any idea of the source of the
problem


Any help, ideas anyone could offer would be appreciated. Reply here or



email me at . Thanks

 

My first thought is for the crankcase pressure building up. Most often that
shows up first at idle, causing billows of blue smoke when idling and for
about 30 seconds after taking off. When the crankcase pressure builds up the
oil backs up into the turbo and dribbles into the exhaust.

Remove the oil filler cap, then unfasten the hose that crosses over the top
of the engine from where it attaches to the side of the turbo intake duct
and try blowing through it. The resistance should be a bit more than you
would expect of the hose itself but not as much as if you were trying to
blow through a soda straw. You should be able to exhale in three seconds or
so. If it does not flow freely, check the hose pieces (no fooling!) and the
oil/air separator box it attaches to under the intake manifold. That box is
held by two bolts and the friction of the two o-rings beneath it. If the box
is plugged it can be cleaned, but not well and not easily. Replacement is a
better alternative if available.

Mike

 

I forgot to mention - that oil pervading the intake system is normal for the
740/760/940 turbos. The crankcase ventilation system sucks the mist out of
the crankcase and reintroduces it ahead of the turbo. It collects in the
intercooler and coats all the ducts.

Mike

 

Interesting, this raises a question for me (please be forgiving I am green)

So if a person switches to synthetic oil is there anything ahead here in the
intercooler which might not be synthetic friendly?

 

I hadn't thought about that when I switched to synthetic <8^P

AFAIK the synthetic oil hasn't been a problem (it's been maybe two years). I
also haven't had to clean the throttle body or idle air control valve since
the change, but maybe that's going to catch up with me.

Mike

 

i looked at the crankcase hose, and they appear to be pretty good, no
oil residue or else.
I blew some air in it as well and it didn't seem to have much
restriction.

Also, I have a small prestone leak, I don't know if it matters.
Else, after my engine runs for a while. once stopped I remove the oil
filler cap, and some little white smoke out of it. I can't say if it's
normal or not.

DO you have any other idea, or should i change oil to synthetic???

Thx
Louis