AOS on 944s2
08-20-2018, 12:51 AM
#1
1st Gear
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AOS on 944s2
Here is an interesting problem. We have the option to buy a 1989 Porsche 944s2 at a good price. Paint and interior are all immaculate and mileage is 90,000. It belongs to an older collector we know and an honest person. The reason the car is being sold is that it burns oil. So here are the facts:
- Under acceleration and deceleration it does not blow any smoke.
- Around town and at low speeds it does not use a noticeable amount of oil
- But at highway speeds and at higher RPM's above 2500 is DOES use oil at the rate of about a quart every 250 miles.
- Compression check gave 190 in first cylinder (which I heard burns hotter) and 195 in all other cylinders
- There is oil contamination only in the first cylinder as seen on the spark plug.
- It did have a valve job at 70,000 miles with new valve guide seals and the upper chain serviced. And it does have a good service history with timing belts done.
I am guessing that the reason that it is burning oil at higher speeds in the number one cylinder is because the Air Oil Separator is faulty. My worry is that it could be an oil control ring on the piston which would be an expensive fix or possibly another problem that that I have not thought of. For the price we are paying fixing the AOS would make it a great deal, fixing piston rings or something more serious would make it a headache. Does the AOS sound like the problem and is there a way to confirm this?
From the symptoms described what are your opinions? Thank you
- Under acceleration and deceleration it does not blow any smoke.
- Around town and at low speeds it does not use a noticeable amount of oil
- But at highway speeds and at higher RPM's above 2500 is DOES use oil at the rate of about a quart every 250 miles.
- Compression check gave 190 in first cylinder (which I heard burns hotter) and 195 in all other cylinders
- There is oil contamination only in the first cylinder as seen on the spark plug.
- It did have a valve job at 70,000 miles with new valve guide seals and the upper chain serviced. And it does have a good service history with timing belts done.
I am guessing that the reason that it is burning oil at higher speeds in the number one cylinder is because the Air Oil Separator is faulty. My worry is that it could be an oil control ring on the piston which would be an expensive fix or possibly another problem that that I have not thought of. For the price we are paying fixing the AOS would make it a great deal, fixing piston rings or something more serious would make it a headache. Does the AOS sound like the problem and is there a way to confirm this?
From the symptoms described what are your opinions? Thank you
08-25-2018, 03:00 AM
#2
Rennlist Member
My 87 944 auto burns oil at highway speeds (4000+ rpm @70 mph) as well and you do smell it.
I'm personally trying to add a proven 200 somewhere in the engine bay to combat this as it drinks a quart every 2 fill ups or 500 miles.
At around town speeds it won't drink a drop. I just think the factory AOS just gets overwhelmed and needs some help down the line.
I'm personally trying to add a proven 200 somewhere in the engine bay to combat this as it drinks a quart every 2 fill ups or 500 miles.
At around town speeds it won't drink a drop. I just think the factory AOS just gets overwhelmed and needs some help down the line.
08-28-2018, 12:04 PM
#3
Rainman
Rennlist Member
Rennlist Member
Blake,
burning oil is NOT a normal feature of a 944.
the AOS does not get overwhelmed on an NA model...
make sure all the orings (2 into the block, and one big one under the black cap) are fresh.
burning oil is NOT a normal feature of a 944.
the AOS does not get overwhelmed on an NA model...
make sure all the orings (2 into the block, and one big one under the black cap) are fresh.
11-10-2018, 09:37 PM
#4
Not sure what an AOS is but will have to look it up now.
My 944 s2 doesnt burn or leak anything from oil change to oil change. Last change was Dec 2017, and I just checked dipstick is at full. Maybe 7000 miles on the oil over the last year and 132,000+ on the clock. All original so far. Time for another change soon but it doesnt look black yet either. I can tell you it is not “normal” for these cars to burn or leak ANY oil. I have always used 10w40 maxlife valvoline synth blend in my 924. 944na and now 944s2.
The 924 was redlined every single day for years driving to work cuz I was young and it was slow and needed to and was so much fun to. The S2 I dont think has ever seen over 4k before a shift so I do baby it a bit more. 924 still doesnt lose oil after 30 years of ownership.
My 944 s2 doesnt burn or leak anything from oil change to oil change. Last change was Dec 2017, and I just checked dipstick is at full. Maybe 7000 miles on the oil over the last year and 132,000+ on the clock. All original so far. Time for another change soon but it doesnt look black yet either. I can tell you it is not “normal” for these cars to burn or leak ANY oil. I have always used 10w40 maxlife valvoline synth blend in my 924. 944na and now 944s2.
The 924 was redlined every single day for years driving to work cuz I was young and it was slow and needed to and was so much fun to. The S2 I dont think has ever seen over 4k before a shift so I do baby it a bit more. 924 still doesnt lose oil after 30 years of ownership.
