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The turbo scavenge oil return line does not go to the oil filter on an '87, it drains into the tank unfitered.
I checked that out with air pressure on mine around a year ago.

If it was going to the oil filter than when I put 120psi of air into the turbo oil return line fitting on the tank, air would have come out of the mulitple outer ring of holes where the oil filter screws on. Thats where oil goes into the filter.
Instead, air came from everywhere else but those holes which proves that oil from the turbo does not go through the oil filter screwed onto the tank.

When I had my oil tank out to clean and paint it, I looked inside as best I could and the only thing that surprised me is there is a large course screen like material in there towards the top half of the tank. I can only guess why it's there and my guess is to act as a partial baffle to try and keep the oil from sloshing around as much when driving hard and or to seperate out any bubbles in the oil.

Old 02-25-2009, 08:12 AM
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Now that it is confirmed that turbo oil is unfiltered in the tank 2 things really concern me:
1) The fact that Porsche designed the system knowing this from the beginning and did nothing over all these years to address this issue with coking
2) The pressure from the cam driven turbo sump pump is very low in my opinion at 1-1.5psi, makes me wonder if that is normal even though the flow rate seems adequate to pump out the turbo drain tank......is that enuff pressure to handle any restriction as the inline filter clogs with oil dinkleberries...seems barely enuff pressure to pump the oil up to the top of the engine oil tank.
So far this is an impressive fix making me wonder when to start doing it to my car.
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Old 02-25-2009, 08:55 AM
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If you follow the recommended shutdown process, there is no problem; and turbos last a long long time when treated right.
Old 02-25-2009, 09:07 AM
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The turbo scavenge pump is a small close tolerance dual gear type pump that having taken it apart and looked at it I believe it could make some oil pressure if it had to.
Thing is there is no orifice or bearing clearance it's pushing oil through. Instead it is pushing a low volume of very hot oil that is full of little bubbles through a piece of hose and tubing around 9mm inside diameter back to a tank.

The only restriction it would have to push against and maybe build some oil pressure would be the inline oil filter some of us have installed.
If you follow the owners manual directions to let the car idle a couple minutes after driving hard to cool off the turbo, and use good oil and change it often enough than there shouldn't be coking and alot of carbonized oil chunks flaking off the inside of the turbo and contaminating the oil... hopefully.

I installed the sysem one 75 micron filter in my turbo oil return line about 4 months ago when I installed a freshly rebuilt K27 HFS turbo and havn't opened it up to inspect and clean it yet.
I'll wait a couple thousand miles, then open it when I do an oil change.
Being under the engine tin where I located it, it will not make any mess from spilled oil when opening it with an oil change bucket on the ground under it.
Old 02-25-2009, 10:01 AM
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Quote:
Originally Posted by sand_man View Post
Yes I caught that he can disconnect the line without losing oil from the tank. I truly don't know the inner-workings of the 930 oil tank, so I don't know for sure if there is a pipe inside that runs up to the oil filter from the tank scavenge pump fitting. Even Porsche has been known to do things that don't make sense. I would indeed feel better if what you say is true.
Keep in mind, that on a cold engine, the dip stick usually reads nothing...granted it doesn't reach the bottom of the tank either. So perhaps the level just wasn't high enough for oil to leak out of that opening
You do have a point.
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Old 02-25-2009, 11:24 AM
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Quote:
Originally Posted by JFairman View Post
The turbo scavenge oil return line does not go to the oil filter on an '87, it drains into the tank unfitered.
I checked that out with air pressure on mine around a year ago.
Correct. I actually had granules of carbon in the bottom of my main oil tank.

Quote:
Originally Posted by fredmeister View Post
Now that it is confirmed that turbo oil is unfiltered in the tank 2 things really concern me:
1) The fact that Porsche designed the system knowing this from the beginning and did nothing over all these years to address this issue with coking
2) The pressure from the cam driven turbo sump pump is very low in my opinion at 1-1.5psi, makes me wonder if that is normal even though the flow rate seems adequate to pump out the turbo drain tank......is that enuff pressure to handle any restriction as the inline filter clogs with oil dinkleberries...seems barely enuff pressure to pump the oil up to the top of the engine oil tank.
So far this is an impressive fix making me wonder when to start doing it to my car.
The pressure is only low because there is no restriction to the flow. I am sure that if the "oil dinkleberries" start to clog the filter, the gauge would show a pressure increase. Also, in this application there would be no point in putting a second gauge after the filter as some have suggested because it would always read very close to zero.

Quote:
Originally Posted by Miguel Antonett View Post
If you follow the recommended shutdown process, there is no problem; and turbos last a long long time when treated right.
Agreed. I am sure this is more critical than many of us realise. I am beginning to think that my problem may have originated with only a handful of "incorrect" shut-downs.

Quote:
Originally Posted by JFairman View Post
The turbo scavenge pump is a small close tolerance dual gear type pump that having taken it apart and looked at it I believe it could make some oil pressure if it had to.
Thing is there is no orifice or bearing clearance it's pushing oil through. Instead it is pushing a low volume of very hot oil that is full of little bubbles through a piece of hose and tubing around 9mm inside diameter back to a tank.

The only restriction it would have to push against and maybe build some oil pressure would be the inline oil filter some of us have installed.
If you follow the owners manual directions to let the car idle a couple minutes after driving hard to cool off the turbo, and use good oil and change it often enough than there shouldn't be coking and alot of carbonized oil chunks flaking off the inside of the turbo and contaminating the oil... hopefully.

I installed the sysem one 75 micron filter in my turbo oil return line about 4 months ago when I installed a freshly rebuilt K27 HFS turbo and havn't opened it up to inspect and clean it yet.
I'll wait a couple thousand miles, then open it when I do an oil change.
Being under the engine tin where I located it, it will not make any mess from spilled oil when opening it with an oil change bucket on the ground under it.
Yes, correct. There's no rocket science involved here. It is just a simple gear pump moving oil from A to B with little restriction.
Having now pulled my filter apart a couple of times this week, I have been surprised at how easy it is to do without spilling oil. I just loosen the two mounting hose clamps, hold the filter vertical, disconnect the outlet hose and unscrew the top end complete with filter element. It's only hand tight (sealed by o-rings) and the oil stays in the housing without spilling.
After all this, I'm almost disappointed that there hasn't been anything to clean out of the filter - but great insurance!

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Old 02-25-2009, 03:20 PM
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