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billjam billjam is offline
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Join Date: Aug 2007
Location: Perth, Western Australia
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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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Bill
1988 Carrera - 3.6 engine (with ITBs, COPs, MS3X) and a whole set of turbo body panels waiting in the attic.
Day job ... www.sspowdercoat.com.au
Memories: '68 912, '72 911T, '80 911SC, '84 911, '85 930, '86 930, '87 911
Old 02-25-2009, 03:20 PM
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