Oil Overfill on SC - What you might not see.

[Jdub]

Just a few pics on what happens on oil overfill and why it pays to keep it at halfway on the dipstick.

Plenum removed - I always unscrew the breather hose at the fill tube and snake it around the back of the engine along with the plenum since you cannot loosen/tighten the breather tube-to-plenum when in situ due to access restriction:



A peek into the oil-soaked CIS Air Flow chamber and sensor plate. The extra weight of oil throws off the balance of sensor plate-to-mixture control unit:



A look-see into the throttle body - not quite as bad:



A look into the plenum and now-removed breather/overfill tube which is being drained of overfilled oil:



We talk a lot about overfilling oil, and often those who overfill their CIS cars forget to remove and clean all related items. It is not difficult, and you are rewarded with both a cleaned-up breather assembly and tighter idle. As a data point, when we did this to a friend's SC we had to turn the idle down. It had been turned up to "overcome" the lumpy idle. A full plug/cap/rotor still had this guy scratching his head. I helped with the oil change and suggested we dig into this possibility. You can see the results, and his car starts and idles like a champ.

[Jdub]

...of the plenum and oil breather tube:

[Kraftwerk]

that is just gross. but noted...

[Howard M]

Many years ago I cut that breather hose on my '76 and placed a Mason jar in-line with the hose. I fab'd an airtight cover with an inlet and outlet.....a home-built air/oil separator before there were so many available from the aftermarket. There was room for the jar on the shelf of the firewall, secured with Velcro, near the breather hose. If I were to do it again I'd buy a proper separator from Jeg's with internal baffles and a drain valve. An easy, inexpensive home project to minimize the oil migration to the intake. I never overfill the oil (ten quarts). And since we're talking oil changes: a Fumoto valve on the oil tank.

[Jdub]

Meant to mention that, before you start this process, idle the car and ensure the idle drops when you remove the oil fill cap. This way, after reinstall, you can confirm the same behavior and know you have cinched everything up w/out an air leak.

[T77911S]

thats form moisture. some say its from short drives where the egine is not up to temp long enough to burn off the moisture or it does not get hot enough.
i went out in my garage the other day and EVERYTHING was covered with moisture. i opened my tool box and all my tools were wet, everything. i thought i wonder if the inside of my engine has this moisture. im sure it did.
also, the oil getting back into the intake like that can be from too much oil, BUT, it can also be from blow-by. thats compression that blows past the rings and out the case, into the oil tank and then blows oil back into the intake.
mine got so bad on my 77 that when i took off the throttle body, oil literally poured out, same with the decel valve. full of oil. (i think that is why it was holding the RPM's up too long).

i never fill my oil all the way up. min to half way is good. remember, there is 10+ qts of oil in there. actually, when i oil needle hits min, i drop a qt in.
when i did fill it up, i went thru more oil.

[Algernon]

Originally Posted by T77911S

i never fill my oil all the way up. min to half way is good.

I assume that is on dip-stick NOT gauge, and is after warm-up?

[jlynch1960]

Probably a stupid question, but why does the breather feed into the intake manifold? Assume it's for vacuum but what is the purpose of the vacuum? No flaming - just trying to learn something I don't know.

[Reiver]

Agree about the moisture as opposed to over fill. Water and oil give you that creamy yellow mix.
Drive them til fully warm.
I'd also agree that an overfill could cause some issues here and should be cleaned up afterward.
Good post.

[Ronnie's.930]

Originally Posted by jlynch1960

Probably a stupid question, but why does the breather feed into the intake manifold? Assume it's for vacuum but what is the purpose of the vacuum? No flaming - just trying to learn something I don't know.

It feeds into the intake in order to burn the oil vapor from the crankcase and oil tank - the vapor is supposedly less toxic once burned in the combustion process.

[SkunkWorks]

Thanks for the heads up. The shop overfilled my SC as well and I've been dealing with a high idle ever since... Any other places to take apart and clean up?

Here's what my airbox looked like for reference,

[safe]

I don't think the OPs pictures are alarming or unusual. You will always have a bit of oil in the intake. The crap in the breather hose is mostly moisture.

[T77911S]

Originally Posted by Algernon

I assume that is on dip-stick NOT gauge, and is after warm-up?

i new i would get someone to bite.

of course the gauge. if you verify the gauge with the dip stick, you never have to pull it again.

[JJ 911SC]

Originally Posted by aerharehying

thats form moisture.

Here we go, Mr. cut & paste, useless piece of caca...

[Jdub]

Great replies - the crankcase vent to oil tank is an excellent point. After reading the wisdom I have advised my buddy to have a comp. and leakdown done with an experienced ear to determine what might be going on.

He did mention a "bad" oil control ring on one cylinder according to the PO, and said it just needed an "Italian Tune-Up" (read: massive Techron/Seafoam injection and a very long spirited drive). I told him that was an old wive's tale.

Oil in the airbox on the SC is a definite indicator since the oil has to get there past the sensor plate and down the "bowl".

[T77911S]

i drove my 77 for quite a while with oil blowing back into the intake, and WAY worse than these pics.
lower oil level does help.