RCinXS

Another thought.

I've seen some guys toss the oil separator screen into the garbage because it looked "rusty".

Suddenly, they are using more oil than they used to. They take the plenum off and it's full of oil.

If the separator screen is not there, oil separation isn't happening and the result could be the exact condition that you have.

RCinXS

Sound like a can of pop being opened slowly?

Hkp7

separator screen is there, hissing is actually constant. One thing I did notice is the cork seal for the oil filler cap is missing. I have had a couple times the oil dipstick pushed out about an inch after test driving. Flooring it several times. Also if this makes sense, when I floor it, it seems to run fine, sort of getting its power back. I know I said earlier I had 150 pounds compression on all cylinders but I am wondering if it is possible to be leaking compression to an oil passage. I am pretty sure the head gaskets were never done looking at the PO's stack of repair bills from the last 26 years. I havent heard more than two 928's run been so long since I heard the last one, but really I wouldnt think a Porsche would even sound like mine. Other than the latest running rough under load, it always seemed to sound like its fighting something. Hard to explain.

RCinXS

Do you hear a mysterious sound when the car has been idling for a few minutes? Almost like a bearing or water pump going bad?

I've seen and heard this. When the oil seperator cap is loosened the sound goes away after the hissing pop can opening noise is over.

The bad bearing sound is from air being forced through the oil separator gasket acting like a reed in a musical instrument. (Could explain the selaer oozing from the separator gasket)
This sound means the crankcase is under a lot of pressure at idle.

I'm not saying that this your problem, but it was the problem on other cars that had the hose routing wrong after doing a top end clean up. You should get a diagram and make sure everything is hooked up right.

RCinXS

I would think that the Oil dipstick popping out would definately count as a sign that you have pressure in the crankcase.

Pressure in the crankcase is a VERY BAD THING! Also explains lack of power. Pistons going down against crankcase pressure don't move very well.

I would count youself lucky that the dipstick popped out and released SOME of the pressure. Buy a lotto ticket. Get a diagram. Route the hoses properly or clear whatever blockage is happening.

Hkp7

Not sure about the bearing sound. Doesent quite sound like that.

Hkp7

Makes a lot of sense about the crankcase pressure, maybe that is why it runs smooth at idle and rough under load. I wonder what could be blocked because it seems I have everything routed correctly according to book.

RCinXS

Check your hose routing with a diagram. I beleive that is most likely what is wrong.

Your engine is / was "fighting" crankcase pressure.

Older American cars overcome positive crankcase pressure using a PVC valve. Your 828S does not.

Proper hose routing will evacuate pressure from the crankcase. Your car will run great again.

RCinXS

You checked it against a book?

Are you sure you had the correct diagram? Hose routing is different, depending on the year AND what country the car was originally intended for. There might even be a diference for a US car in California.

Hkp7

there is a check valve t with a 928 part number on it going from the oil filler cap hose to the throttle body that the other end goes to the air box. the valve is in the hose to the air box the hose to throttle body from the oil filler lid is a straight shot.

RCinXS

Routing 84

RCinXS

And this

RCinXS

Gotta go rake leaves. Maybe somebody else has thoughts?

Landseer

Some related information.

Pictures didn't turn out well at all, but I set this car up using the attached info.


Kind of a shot in the dark to help you.

Hkp7

Thanks for everyones help. It seems everything is routed correctly on my end. I must be dealing with some type of blockage. I will keep digging.