Oil out of crankcase vent tube

[scooterdup]

1959 Chevy Apache with original inline 6.

Have oil coming out of crankcase vent tube. Have seen other posts on this subject that recommended removing and cleaning vent tube. Have also seen recommendations to clean oil cap to make sure it is venting properly.

What is best to use to soak / clean these parts?

[whitedog76]

Do you have slits in your valve cover or a vented breather cap?

[Jesse Z]

Isn't that a result of excessive piston ring blow-by pressurizing the crankcase? I've heard of dipsticks blowing out of engines.

[scooterdup]

Originally Posted by whitedog76

Do you have slits in your valve cover or a vented breather cap?

Vented cap.
Will clean it and vent tube...and also check compression.

[whitedog76]

It’s been awhile since I pulled apart a 235. If I remember correctly, there’s a baffle plate and steel wool like material inside the crankcase. It could be possible that something is missing there.

Since you have a vented cap, maybe try and see what happens if you block off the draft tube.

Of course, a compression check will tell you a lot too.

The guys over at Stovebolt.com have the 235 down to a science, if you haven’t already been there.

[dsraven]

assuming your crankcase breather system is functioning properly and free flowing in all areas
-valve adjustment
-pull all the spark plugs and check their condition (oil soaked, dry, brown, black etc)
-cylinder leak down test
-compression test, dry
-compression test, wet


compression tests can be a bit misleading if the engine has an oil consumption problem because they can mimick a wet compression test, sort of sealing the rings with oil getting past the oil control rings. best do do the leak down test dry first while everything is still dry inside there like normal. then the dry comp test, then the wet (with oil squirted into the cylinder prior to compression test). the comp test is done with all spark plugs out, the throttle tied wide open and the coil power wire off. have an extra battery of some booster cables ready so the cranking speed stays the same for all the comp tests, otherwise the results are skewed. of course it is always best to start with a valve adjustment so you also don't get skewed results and each cylinder has it's best chance.

[mr48chev]

That is the best set of instructions on running a compression test I have seen on the net and the exact way it should be done.

I would expect worn rings and excess blowby that builds pressure in the crankcase but you normally see signs of that with the engine running with the breather cap off and sending smoke signals out the breather cap hole. These engines didn't get huge mileage numbers before needing a rebuild and going much past 60/70 K without a rebuild or valve job was a cause for bragging rights at the coffee club. 100K without a rebuild might have gotten mention in the home town weekly paper back then. You can't expect the miles before needing work that you do now.

The leak down test would be a good thing to perform or have performed if the compression test doesn't show an obvious issue. You don't need a huge compressor to do that. You do want it relatively quiet around the work area so you can hear any leak along with seeing it on the gauge.

[vintovka]

Near the end of the life of one 235 i had the blow by got so bad would push a quart out the tube in less than 100 miles. It later seized.

While you're at it always make sure the tube is fully seated and locked down tightly. Had one come loose and leak oil all over sunset strip in Hollywood.(circa 1968) Got so low it developed a rod knock and the Hari-Krishna types were pissed after slipping on the oil slick.

[OrrieG]

Originally Posted by mr48chev

These engines didn't get huge mileage numbers before needing a rebuild and going much past 60/70 K without a rebuild or valve job was a cause for bragging rights at the coffee club. 100K without a rebuild might have gotten mention in the home town weekly paper back then. You can't expect the miles before needing work that you do now.

That is why people traded in cars for new after about 50-60K miles back then. In 68 I bought a second owner Impala with 55K for $495.

[mr48chev]

True there, I knew "older" guys who traded before 40K in the early 60's Most guys didn't rack up the miles then that we do as a norm now though. In the 50's I had a friend of mine have to change schools because his dad wouldn't drive the extra 8 miles a day to work that his new job took. They moved to a house within a mile of where his dad's new job was.