Crankcase Filling With Oil!

[mbrown]

Gentlemen...

The story:
1. The crankcase breather hose creased and blocked itself off without me noticing it. I went for a drive with no problems. I do remember hearing a bubbling noise inside the engine when I shut it off. Thought about it for 10 seconds and put it out of my mind.
2. The next time I start the engine I notice a few splashes of oil on the garage floor and open the engine lid. Since I have electronic ignition, I have removed the distributor and replaced it with a press-fit plastic plug with o-ring. This plug had popped out! This alerted me to the fact that I must have pressure in my crankcase so I check the breather hose. Doh! It's creased.
3. I removed the crankcase breather hose and replaced it with a small length of hose topped off with a very small air filter (no further blockage possible). Also pressed the distributor plug back into its hole.
4. I started the car and about 30 seconds after starting, oil began pouring out of the crankcase breather filter!!

Help! What have I done!
Did I just fill the entire engine with oil?
Please tell me that the engine oil pump is still working!

Any suggestions to fix this problem greatly appreciated.


Regards

Mike

[911pcars]

This was the same situation on a race motor last week, and it's the same solution.

Don't bypass PAG's crankcase vent routing. The crankcase breather hose first goes to the oil tank, then vents into the intake. Allow the oil tank to reduce oil velocity before venting it. Get a replacement hose and try again.

Another possible contributing scenario is that the crankcase blowby is exacerbating the situation. Perform a compression test to confirm the engine is in good condition.

Sherwood

[304065]

Sherwood, I heard the same thing: at high RPM oil fills up the crankcase breather hose over to the oil tank.

[mbrown]

Gentlemen...

Thank you for your comments.

I added the crankcase breather into the system. Oil was still being transferred into the oil tank, even at idle. There was quite a lot of airflow out of the oil filler. Guess I'll be tearing down the engine in the near future.


Regards

Mike

[911pcars]

Mike,
Just to clarify, the crankcase breather hose connects to the oil tank. From there, a hose on the filler pipe connects to an add-on breather tank. From there, it can vent to atmosphere or be routed to the air intake system.

If you still get copious amounts of oil into the breather tank at idle, I'd suspect worn rings. Perform that compression test and let us know.

Sherwood

[mbrown]

G'day Sherwood...

I performed a compression test and got 120 to 130 psi for all of them. This could be low, but the engine has the turbo 97 mm pistons and cylinders, thus low compression.

What do you think?

Is there any other reason you can think of that would cause the oil to pump out the crankcase breather?

Should I split the crankcase to check everything inside when I swap out the pistons & cylinders? Would rather not of course.


Regards

Mike

[911pcars]

Mike,
Oil will blow out of the crankcase hose regardless of the compression. That's normal. That's why that hose routes to the oil tank to reduce the oil velocity and help separate oil from vapor. By the time vapor reaches the end of the hose attached to the filler tube, the storm should be over. That's normal. A race engine at WOT (wide open throttle) will produce more than normal blowby, but that's fairly normal under high-rpm conditions.

Have you tried venting the crankcase via the above path?

An engine with a lot of blowby will have excessive crankcase pressure which usually shows up as excessive oil in the air cleaner (factory path) or in an aftermarket breather tank.

Did you perform the compression test wth the engine at normal operating temperature? Just to be sure, conduct a leak down test. If disassembling the engine were easier and faster, I'd suggest you do that, but of course it isn't. Do the easier-to-do-stuff first. Is your engine naturally aspirated or boosted? When boosted, the effective compression ratio is dramatically higher (depending on boost pressure) than a normally aspirated engine. More pressure will increase combustion temperatures and place more stress on the piston rings.

Sherwood

[mbrown]

G'day Sherwood...

I am venting the crankcase into the oil tank and at idle I can see oil flowing into the oil tank through the oil filler mouth. I also have another crankcase vent coming from the where the distributor was, going into the oil tank. The oil tank cap is off to allow the system to vent to atmosphere until I set up an add-on breather tank.

I performed the compression test on a cold engine. The engine configuration is 3.3L turbo pistons, cylinders, rods & crank. Everything else is 1980 3.0L SC engine components. I have turbocharged it with a 1 bar wastegate spring. I have a Megasquirt II V 3.0 engine computer and FORD EDIS ignition system.

I also have a turbo oil scavenge pump extracting oil from the turbo oil drain and pumping it to the sump plate. I operated the turbo oil scavenge pump without the engine running to determine if this pump was causing extra crankcase pressure. It was minimal, only after about 30 seconds of my hand over the oil tank filler could I detect a flow of air when I slowly lifted my hand off to break the seal.

I am resigned to the fact that I will have to replace the pistons and cylinders. At least I will have a 'good as new' engine.


Regards

Mike

[911pcars]

Mike,
The hose shown. Does that connect the crankcase to the filler tube? The proper crankcase hose routing should go directly to the tank, not the filler tube. There should be a second hose from the filler tube to a catch can. That routing path helps separate the oil.

1 bar (approx. 14 psi) on a stock SC engine is pretty high. Have you confirmed the real boost pressure? Because of this, I would suspect something is amiss (i.e. broken rings).

I would repeat a compression and leakdown test on a hot engine. Once you confirm the diagnosis, proceed with the repair.

Sherwood

[mbrown]

G'day Sherwood...

That hose shown comes from the crankcase breather and goes to the filler tube. I'll check the plumbing this weekend (if not beforehand) and correct it to route into the oil tank.

I'll repeat the compression test on the warm engine. I don't have the equipment for a leakdown test. Perhaps it is worth purchasing myself.

Thank you very much for you help so far.


Regards

Mike

[mbrown]

G'day Sherwood...

I've removed the engine and started the teardown. I should have the task finished by the weekend. I'm in the process of tracking down cylinders and pistons.

As part of the rebuild I'll re-route that oil breather hose to its correct location.

Thank you for your input.


Regards

Mike