Oil smoke 78, 911 3.0CIS

[911oslo]

Hi guys

I tried to search about this but did not find the answer to my problem.
I bought a 3.0 cis engine which i rebuilt and mounted in the car summer of 2008. New walve guides were mounted in the original walveguides as that was what the machine shop recommended. The pistons and cylinders were re used but with new rings. Summer of 08 the engine was perfect, no leaks, normal run-in oil consumption

The car is not used or started in the winter.

After driving it for a while in 08 i notest som blue smok fra exhaust when the engine was revving down i gear. This was reduced during the summer, but never disappeared.

This spring it was exactly the same as the previous spring. A little blue smoke when decelerating in gear but not to much.

Yesterday when i was driving i notested a little cloud of blue smoke every time i was revving the engine above 4000 rpm.

Does anybody have some tip as to were or what to check?

Thanks - Arnfinn, Norway

[Sigurd]

What is the oil level with a warm engine? Overfilling could be a cause.

[E Sully]

Do you have any idea how much mileage was on the engine you purchased?
Have you done a compression check? It is possible that the new rings did not seat well. Do you know what type of cylinders, nikasil or alusil?
You installed new valve guides, but did you reuse the old valves? Exhaust valves should usualy be replaced, they have a tougher life than the intakes. If the stems of the valves were worn you would get oil smoke on decelaration.

[911oslo]

The oil level is at max on the dipstick, on the other side of the marking on the stick the oil is above... I use 10W40 semi synt oil.

All of the walves was changed during the rebuild.

If it is the rings that not have seated well, what need to be done to cerrect it?

thanks for helping me!

[Flieger]

Most people like to keep oil midway between "MIN" and "MAX" markings. Try that and your oil smoke should get better, unless it has already collected on the heat exchangers.

[longhornchris04]

How hot is summer in Norway? I ask because Bruce Anderson's book recommends 15W-40 or 20W-50 for 'higher' temperatures. The thinner oil may be pulling through the rings and valve guides.

[911oslo]

The summer temperature here is 50 - 87 degrees Fahrenheit.

To night a was working on the car to try to solve the problem.
I noticed that there was little or no pressure coming out of the hose in the oil tank which comes from the crank ventilation. There was also little or no pressure in the hose from the tank to the inlet.

I took out the whole inlet system and checked the crank hose. The hose was a little bent, so i bent it out and mounted it again. I also took out the red part on the photo below and cleaned it. When i was done reassembling the suction was highly improved.

I also changed the oil. I took out approx 9 liters. 1,8 of them was in the engine sump. I filled it up with 8 liters and drove home. The oil level is now between min and max.



could blockage of this "filter" explain the blue smoke?

Thanks - Arnfinn

[911oslo]

could blockage of this "filter" explain the blue smoke?

[911oslo]

AHA! I found the problem!

On Friday i took out the engine. On Saturday I took the engine apart. The problem causing the oil smoke was loose valve stem seals on cylinder 1, 2 and 3.

I have ordered the part so now I just have to wait, than lots of work awaits.