Oil in the airbox

deserttoad · 12-04-2014, 11:33 AM

I am new to the Porsche world (other than a 914 in high school) We recently bought a '79 Euro. After a little work (Alternator, rotor, relays, misc electrical) it is running fantastic. I am getting ready to replace the fuel lines and found quite a bit of oil in the airbox. Seems to be pretty well distributed. Sounds like this is somewhat common, but I'm worried about the rings. PO didn't have any records of service, as they had recently gotten it from another person. Would a compression check help sort this out?

We didnt pay much, but hate to start putting money into it if it isn't worth it.

Thanks!

Linderpat · 12-04-2014, 01:36 PM

That does not look like the normal amount of oil -I haven't seen that much before. Definitely you should do a compression check. There is always some oil, and typically more than most people think, due to blowback from the combustion process. What you have seems far in excess of that however.
One item that helps the typical case is a baffle that is designed to placed under the oil filler neck,. Here is a source for it: New product - Oil baffle and gasket kit - 928 Classics

Danglerb · 12-04-2014, 02:00 PM

The only reason that oil would be in the filter box is from a backfire blowing oil that often accumulates in the U tube under the throttle, at least that I can think of.

BTW a 79 Euro isn't mechanically different from the US model, just stuff like marker lights on the fenders behind the front wheels.

harborman · harborman's Garage

You did not give the mileage on the car. A 79, getting pretty old. Blow by might be your problem. I do not have any oil in my air filter, none! What is the history on the car?

deserttoad · 12-04-2014, 10:57 PM

The odometer reads 130,000 km. but it only work occasionally - electrical problem in the dash, also on the list.

The car fires right up and has amazing power, feels like it would do 120 all day long. (Gotta love living in the country).

Perhaps I will learn more when I remove the plenum? Spider? Intake? Not sure how it comes apart, bought the service discs from roger at 928srus.

The amount of oil scared me, fingers crossed. This seems like a great forum, thank you all.

stepson · 12-04-2014, 11:21 PM

Isn't it possible that you are or were getting blow-by from the rings being gummed up? Did this car sit for an extended time? If so, you can search the forum for methods that others have used to clean and free up the rings. I don't think there was anything just real difficult about doing it. Maybe Seafoam or MMO or something like that into the cylinders?

It's also possible that you may have already freed up the rings just by driving it more.

Have you done a compression test yet? Please get one done and post the results here.

deserttoad · 12-05-2014, 12:03 AM

Stepson, great advice. I ran MMO in a half tank of fuel, car did seem to run better, certainly had more power.

What is the best way to get access to the plugs for a compression test? Certainly the next thing on the list.

Thanks again

You should I'm a farmer and an old car guy, 1930 Model A, 1951 International pickup, 1967 Jeepster, 1968 Triumph. This Porsche project has me a bit nervous, glad this forum exists.

riber.bentsen · riber.bentsen's Garage

Quote:

Originally Posted by harborman

You did not give the mileage on the car. A 79, getting pretty old. Blow by might be your problem. I do not have any oil in my air filter, none! What is the history on the car?

Your '86 has a completely redesigned oil return system, this '79 has a hose going straight to the air filter box (the one running alongside the spider intake plenum), so oil in the filter is very common.

This example is in excess though, the normal amount being a 'skidmark' on the filter and a thin film inside the airbox.

Many good replys already as to the reason. Clean it up, replace the filter and drive is some more. If it returns in the same quantities I would investigate further, but as it stands it could very well be gummed rings or other misc. stuff from sitting so long.

The oil-baffle from 928 Classics seems to be the most well-engineered on the market today. Certainly better than the flat one from 928 MS...

Linderpat · 12-05-2014, 03:41 AM

I just put that baffle on my 78, and I already notice a big difference. I used to get a fairly large amount of oil in the airbox, and now it is way down.

harborman · harborman's Garage

One way to free up stuck rings is to put a few Oz., of Marvel Mystery Oil into each cylinder through the plug holes. Let it sit a few days, then turn the motor over with plugs out to blow out any extra oil. Also put the Marvel into the crank case, maybe a quart in with the regular oil. I would first do a compression test before anything, write down your readings. After doing the Mystery Oil take another compression test to see if any readings changed.

Linderpat · 12-05-2014, 05:52 AM

^^ This.

Pete R · Pete R's Garage

That's pretty normal. They only routed the oil vent tube to the airbox for a couple years. It soon went to the throttle body. You motor is probably getting a little tired but it's not a big deal. You could install a catch can that would remove the problem or maybe try a different oil that is less prone to vaporizing. A leakdown test would be more informative if you were inclined to test anything. I wouldn't worry.