The Stovebolt Site Forums The Shop Area Engine Shop crankcase ventilation tube

I have a 54 3100 I notice the ventilator tube on the right of the engine there is a canister attached to it. I figure that cannister may need some service. The tube has a clamp attached to it and that's attached to the engine block.. Is the cannister just forced into the block i don't see any type of fastener on it... anyone have the answer out there....Thanks Peter

Crankcase breather.
There is probably just some steel wool looking stuff in the can.

I don't know if there is anything inside of it since a common way to clean them out is to throw them in a fire.

But that is interesting... I'd like to know if there's anything in there myself. Don't gasses just go OUT through that tube?

To go a little further with this, has anyone ever had a road draft tube that they know was clogged up? My 1954 235 engine blows some smoke out the exhaust, so I'm sure its pretty loose inside, but the oil filler cap on the valve cover bounces around visibly when the engine is running, emitting little puffs of blue smoke.

I'm hoping that the road draft tube is clogged rather than this being a case of severely worn piston rings. The engine runs fairly well and does have poser.

underdog is right. There is a wad on "metal stuff" inside the breather, much like a coarse scouring pad. I took a junked one apart one time. As Czechman says, the old timers used to burn the oil residue out in a fire. Breathers would get stopped up and you'd get leaks at all kinds of places.

As an engine runs, the crankcase changes internal volume as pistons move in the cylinders. Hold your hand under the breather tube with the engine at idle and you can feel an in and out puffing.

Roadmarks, while you are correct that the internal volume changes, it doesnt change by a noticeable amount, because for every piston going up, one is coming down. The minute variances are due to piston slap, etc.

The main culprit is blow-by, and on older engines it is more than new engines due to ring and valve seal wear. The crank case vent is meant to expel the gases. The metal mesh inside gives the oil vapor a place to condense and turn back into oil dropplets. For todays engines, the PVC (Positive Crankcase Ventilation) valve is used to draw engine vapors into the intake to run them through the combustion process.

Burning the tar-like oil out of the canisters was common. So was soaking in gasoline or other solvents.

For diesels, a passive system is still used today, now with a small drain tube back to the oil pan to catch the oil.

Turbocharged engines expel more blow-by as BMEP's are higher.

Hope this helps.

To remove it unbolt the bracket and pull it out. You may need to twist and pull at the same time to get it started.
Cleon

Well lots of info I will take it out and soak and clean it out it may be full of guk... thanks again Peter

This was discussed a couple of months ago and I don’t think there was ever a definitive answer that came of it. The subject was excessive oil consumption.
What Scott says only makes sense i.e., that there is a course Steel mesh inside to keep the oil mist from simply blowing out the vent tube. I do not have one to sacrifice to find out if it did have a mesh or simply had a baffle. I would like to hear from anyone that has cut one apart, maybe a picture or two???
It seems to me that with out the mesh you would loose a lot of oil at hiway speeds.
Denny Graham
Sandwich, IL

FYI - Steel Brillo pads can be used as the mesh

It's a simple enough procedure to carefully grind the top off a road draft tube, clean it thoroughly, repack it with coarse steel wool, and weld the top back on. In case the original top is damaged, just replace it with a proper-sized freeze plug and weld or braze it in place.

The road draft tube develops a vacuum at the tapered end of the pipe when the road speed is above 30 MPH. This draws air in through the slots in the valve cover, and ventilates the crankcase by pulling air down past the pushrods, and out through the road draft tube. It definitely needs to be free-flowing.
Jerry