Oily plugs from overfilling engine with oil?

[psjoe]

I am looking at a 78 SC that had an engine rebuild 30K miles ago. The owner disclosed that the car is using 1qt of oil every 5-600miles. Based on the oil usage the owner took it to a local p-car shop to be evaluated. The evaluation showed good leak down numbers (all less then 6%), compression numbers from 120-125, and that a few spark plugs were oily. The evaluation also stated that the engine had been overfilled with oil. After speaking with the owner he used the dash gauge to determine oil level not the dipstick which lead to the engine oil overfill.

The one thing that bothers me are the oily plugs. I searched on oily plugs and found that failing oil control rings are suspect. The rebuild invoice on this engine shows new rings but no new P/C set.

In addition, the owner claims that car starts right up, idles well, and does not smoke.

My question is : Can consistently overfilling the engine cause oily plugs? .

Thanks -Joe

[2.7RACER]

The numbers quoted to you by the owner do not add up. Compression numbers at 120/125 are low. At least 20 lbs low.
A leak down test would show higher than 6%. More like over 10/15%.
Consistently over filling the oil will cause oil smoke at start up and there will be a sign of oil in the intake.
Did the owner produce paper work supporting his claim of a rebuild 30K miles ago?
The owners story simply does not pass the smell test.
Get your own compression test.
If the compression test is 120/125 lbs. it is likely the motor was not rebuilt 30k miles ago.
Sounds more like a tired SC motor, due for a rebuild.

[redcoupe86]

If it was me my gut would be screaming pass.

But if you're really interested and you can drive and see the car, ask to start the car after it has set the night and make sure you start if from cold jump out the car and take a look at what going on. If it smokes a bunch then you don't have to go any further (unless you're a glutten for punishment.) If you OK with engine work then negotiate well.

At the very least if you're still interested you should get another opinion.

[Loaded]

my 86 had 145psi and less then 10% leak down.

as for your qustion and reading others here and at ****list its common for oily residue.

Plus be sure to drive it and look at the plugs after driving it to temp for a good while.

[Early_S_Man]

Joe,

It sounds like that engine must have had a 'hard' 30K miles! The compression numbers are very low for a rebuild that fresh! I concur that another compression test is needed, with a new or fresh compression test gauge that has been calibrated or compared against a reference gauge at 100 psi and 150 psi.

But, to answer your question ... YES, consistant, continuous overfilling of the oil tank can lead to the extra oil being ingested through the airbox, smoking due to the oil burning in the combustion chamber, and oil fouling of the spark plugs!

The reported oil 'consumption' may not actually be that great if the oil level is maintained at the correct midway point on the dipstick.

[psjoe]

Thanks for confirming that oily plugs can result from consistant overfilling. The rebuild on this car was 30K miles ago but back in 1992. I pasted the invoice detail below FYI.

I agree something is fishy here. I may have brought the price down to $9K from $14K based on this info. But even at $9K I am not sure I want to get into this.

On the other hand I could buy for $9K and just drive it and see how it goes.

As you can tell I am a bit indecisive.

Thanks again - Joe

Date 03/01/1992
Parts List
Quantity Part Number Part Description Cost Total Cost

1 93010090104 GASKET SET, ENGINE LOWER 911 133.95 133.95
12 93010432101 GUIDE, STANDARD 911 13.75 165.00
1 93010113803 BEARING, NOSE STD 911 81.70 81.70
1 93010190100 BRG MAIN STD CRNK STD, 911 343.60 343.60
1 93010314800 BEARING SET ROD STD 181.20 181.20
1 916101135 BEARING SET, COUNTERS 911 39.00 39.00
1 93010398600 RING SET, 911 3.OL (6) 315.60 315.60
2 91110552950 TIMING CHAIN (W/LINK) 911 53.40 106.80
1 93010723302 HOSE, OIL TANK 911 28.05 28.05
1 93010090703 GASKET SET, ENGINE UPPER 911SC^3.0L 365.99 365.99
1 91110522205 SLIDE RAIL, BROWN (1 REQ.) 5.40 5.40
5 91110522206 SLIDE RAIL, BLACK (5 REQ.) 5.40 27.00
1 93010190200 SUMP PLATE (NEW STYLE) 911 18.55 18.55
12 93010117002 STUD CASE - HD DILAVAR 911 39.85 478.20
12 91110117200 STUD 7.30 87.60
12 91410317100 BOLT, CON ROD 11.75 141.00
12 90110317300 NUT, CON ROD 1.80 21.60
3 NS893431 PORSCHE GASKET MAKER-ORANGE #574 27.90 83.70
1 93010591201 TENSIONER UPDATE KIT LT^&^RT 911 512.00 512.00
2 90142325300 BUSHING, THROTTLE SHAFT 2.15 4.30
1 93060290701 CABLE, DISTRIBUTOR 26.99 26.99
1 91111015400 BUFFER, AIR CLEANER '77 911SC 5.35 5.35
1 91121127400 AIR PIPE '77 911SC 15.90 15.90
1 91121152200 AIR PIPE '77 911 SC 23.60 23.60
1 91121155300 AIR PIPE '77 911SC 5.40 5.40
1 90121119600 AIR HOSE 11.40 11.40
1 91121127300 AIR HOSE 7.55 7.55
6 99908500102 NUT, EXHAUST 1.05 6.30
6 91160931100 CONNECTOR, SPARK PLUG 20.85 125.10
1 91162415103 BLOWER MOTOR, HEATER 226.95 226.95
1 91121127202 BLOWER HOSE 4.20 4.20
1 91110700805 PUMP, ENGINE OIL 911 651.05 651.05
6 91110313200 BUSHING, CONN ROD (WRIST PIN) 6.30 37.80
1 9.5*725 V-BELT 6.35 6.35
1 91111018502 AIR FILTER 911 73-83 (LX261/AG147) 16.59 16.59
1 LM2003 FUEL INJECTION PURGE 22.89 22.89
1 91160623000 SWITCH, OIL PRESSURE WARNING 11.35 11.35
12 BRAKE CLEAN SOLVENT 5.12 61.44
50 110-08 8MM NI-LOK NUT 0.28 14.00
84 146-08 8MM FLAT WASHERS 0.04 3.36
26 110-06 6MM NI-LOK NUT 0.25 6.50
22 128-06016 6X16X1.0 BOLT 0.20 4.40
20 146-06 6MM FLAT WASHER 0.04 0.80
1 ELECTRICAL SHRINK TUBE, ELECTRICAL CONNECTORS 4.75 4.75
1 S04060 HOSE CLAMP - 40-60 1.32 1.32
6 S05070 HOSE CLAMP - 50-70 1.38 8.28
1 NPN PAINT AND PAINT MATERIALS 25.00 25.00
1 NPN ALUMINUM CLEANER, ONE GALLON 16.00 16.00
4 90110735101 OIL RETURN TUBE 13.70 54.80
6 W7DC SPARK PLUG COPPER OEM. 2.20 13.20
1 91111119101 GASKET, EXHAUST 1.90 1.90
1 91155623906 SOUND ABSORBER 66.72 66.72
1 G000602 GREASE, CONSTANT VELOCITY JOINTS 6.50 6.50
1 93010776400 OIL FILTER 911, 72 ON (PC260/0C54) 12.31 12.31
1 91151233102 DECK LID SHOCKS, REAR 28.25 28.25
1 12.5*1125 V-BELT, AIR CONDITIONING 11.64 11.64
14 20W50 MOTOR OIL RACING 2.28 31.92
1 NPN GASOLINE 10.00 10.00
1 SHOP SUPPLY WHEEL WEIGHTS (STICK ON) 1.90 1.90

Total parts: 4730.00

Labor
Hours Description Total

50 REPAIR WORK (SEE NOTES) 2550.00
0.4 WHEEL BALANCE (TWO FRONT TIRES) 20.40

Total labor: 2570.40

Sublet
Description Total

SHIPPING/HANDLING CHARGES 30.92
MACHINE WORK 442.80

Total sublet: 473.72

Notes
REMOVED ENGINE AND TRANSMISSION. DISMANTLED ENGINE. DISMANTLEDì HEADS. CLEANED ALL RELATED PARTS. REPLACED ALL GUIDES. REPLACED ALLì CASE STUDS (INTAKE SIDE - REGULAR STUDS, EXHAUST SIDE - DELIVAR STUDS) CUT VALVE SEATS. FACED VALVES. SET SPRING TENSIONS. POLISHEDì CRANKSHAFT. INSTALLED NEW ROD BEARINGS. INSTALLED NEW MAIN BEARINGS.ì INSTALLED NEW RING SET. INSTALLED NEW NOSE BEARING. INSTALLED NEWì AUXILIARY SHAFT SHAFT BEARINGS. INSTALLED NEW OIL PUMP. INSTALLEDì NEW TIMING CHAINS. INSTALLED CHAIN TENSIONER UPDATE KITS. REPLACEDì OIL RETURN TUBES. REPLACED SUMP PLATE. REPLACED OIL TANK HOSE.ì REPLACED THROTTLE SHAFT BUSHING. REPLACED DISTRIBUTOR CABLE. REPLACEDì ALL ENGINE HARDWARE. REPLACED ALL AIR HOSES. REPLACED BLOWER HOSE.ì REPLACED REAR ENGINE BLOWER FAN. REASSEMBLED CASE. REASSEMBLED ALLì CYLINDER HEADS. BEAD BLASTED ALL OUTSIDE SHEET METAL AND REFINISHED.ì REPLACED OIL PRESSURE SWITCH. REASSEMBLED ENGINE. REPLACED OILì FILTER. REFILLED ENGINE WITH CASTROL 20W50 RACING MOTOR OIL. SET CAMì TIMINGS. ADJUSTED VALVE LASHES TO SPECIFICATIONS. REPLACED SOUNDì PROOFING PAD. REPLACED AIR CLEANER BUFFER. REPLACED AIR FILTERì HOUSING. REPLACED SPARK PLUG CONNECTORS. REPLACED SPARK PLUGS. SETì SPARK PLUG GAPS TO SPECIFICATIONS. FLUSHED FUEL INJECTION SYSTEM. SETì CO CONTENT TO SPECIFICATIONS. SET IGNITION TIMING TO SPECIFICATIONS. ì REPLACED AIR CONDITIONING BELT. REPLACED ALTERNATOR BELT. SETì TENSION OF BELTS TO SPECIFICATIONS. REMOVED AND REPLACED REAR DECK LID SHOCK. BALANCED TWO FRONT TIRES. THE FOLLOWING WARRANTY APPLIES ON THE ABOVE DESCRIBED ENGINE WORK:ì WARRANTIED FOR ONE YEAR OR TWELVE THOUSAND (12,000) MILES, WHICH EVERì COMES FIRST, TO THE CURRENT OWNER OF THE CAR, PROVIDED THAT THEì FOLLOWING INSTRUCTIONS ARE FOLLOWED THROUGH WITH, BY THE OWNER. NOTE: PLEASE RETURN CAR WITHIN 1,000 MILES FOR OIL AND FILTER CHANGEì AND VALVE ADJUSTMENT. ALL LABOR WILL BE WARRANTIED AND CUSTOMER WILLì ONLY BE RESPONSIBLE FOR THE PRICE OF THE OIL FILTER, MOTOR OIL, ANDì CAM COVER GASKET KIT AT THAT TIME. THANK YOU!


Thank You!

You are entitled to the return of any replaced parts except those that must be returned to
the manufacture under warranty agreement. If you do not want the parts, sign below:
-----------------------------------
I certify that this vehicle has been tested or test driven when needed and that the mechanic's
work was performed satisfactorily. ------------------------------------


Total Parts: 4730.00
Total Labor: 2570.40
Total Sublet: 473.72
Total Tax: 236.50

Total: 8010.62

[Nostril Cheese]

"installed new ring set"

seems to me, if it had Alusils, that this would be the culprit...

[azasadny]

It bothers me that the owner didn't know the proper way to check the oil level. What else didn't he know how to do properly?

[Gunter]

Looks like a regular rebuild with a big question mark on what type P/C's are in there.
If they are Alusil, it's a big gamble for the future.
Get an independant PPI including compression/Leak-down.
New chains with link? Normally, with the case split, solid chains are used.
Doesn't look like new chain sprockets were used on the I-shaft and that would really bother me because of a bad and costly personal experience.
New chains on worn sprockets will destroy the tips of the teeth.

If a PPI comes back with reasonable numbers for compression etc, AND it can be confirmed absolutely that the P/C's are Mahle (Nikasil) it might be o.k.

Without confirmation on the P/C's, you are facing a possible $8K repair bill in the future.
If you don't do a PPI, you'll have yourself to blame.

[psjoe]

More info-

Another leakdown was done on this car and came back with kooky numbers, prompting the test I mentioned above by another shop. The first set of numbers were 1-15%, 2-3%,
3-30%, 4&5- 4%, 6- 27%.

Here is some additional info on the car:

1978 Porsche 911SC

Current Mileage: 138,123
Sunroof
Air Conditioning (needs charge?)
Complete engine rebuild at 109K miles, March 1992,(have 3 page invoice, $8000)

Complete paint and body restoration at 127K miles:
Porsche Baltic Blue metallic with clear coat (special order code 37B from 84-89 Carrera)
Hood and hatch clear coat appear not to need wet sanding
Original color was Cashmere Beige (code 502)
NO sign of original color anywhere on car!
All body seals and rubber replaced
Euro style headlights
New front and rear glass
New headliner and visors
New interior rear deck/speaker enclosure
New dashboard
993 power seats:
Driver seat needs new fore/aft switch
Original seats available
930 style steering wheel:
Original wheel available
Blaupunkt AM/FM, CD/MP3-CD player and speakers
Yokohama AVID V4 tires (P205/55R 16 front, P215/50R 16 rear)
Original correct black center Fuchs wheels

Complete transmission overhaul at 127K miles, November 2002

Various invoices dating back to 1980s showing maintenance and repairs

I have owned the car since August 2005, always garage kept, never driven in rain or wet.

[Gunter]

Originally posted by psjoe
More info-

Another leakdown was done on this car and came back with kooky numbers, prompting the test I mentioned above by another shop. The first set of numbers were 1-15%, 2-3%,
3-30%, 4&5- 4%, 6- 27%.

So, which test to believe?
I think you'll need another one done by a shop with Porsche experience.
Oil consumption of a quart in 5-600 miles is slightly high for a rebuild.
Oily plugs could be from overfill but also failing rings on Alusil P/C's
Is there any smoke at all after the engine is hot?
With an OX tester in the exhaust, the mixture can be set and if it burns oil, it should show up.

Overall, the car sounds nice and was looked after but the issue of what P/C's are in there is not resolved.

[petrolblue83911]

If the owner was chronicly over filling the car with oil, the 500-600 mi/qt may not be accurate,-the car may be burning less, the owner may have been improperly checking the oil, putting too much in etc...

-could be a better motor than the owner thinks.

-or not.

[psjoe]

Petrol-

That is the the crux of the issue.

The last shop that got the okay numbers was a reputable p-car shop.

The engine may be okay. I wish I had a crystal ball. It's enough doubt to kill the deal for me.

Thanks -Joe

[Gunter]

Any chance the owner could find out from the shop that rebuild the engine what type P/C's?
All around, the car sounds clean but you need to have an independant, thorough PPI done.
I would make a serious offer with subject to inspection and go for it.
If nothing major shows up, it's worth it.
For $9-10k, your'e getting a good paint job, rebuild motor, rebuild transmission and the owner sounds honest.
A clean SC is worth $10K.

[Early_S_Man]

Joe,

These days, most $9K 911s are going to need attention to some expensive issues in the near future ... it sounds like the seller knows he has a car with engine issues, and has adjusted the price accordingly.

Find out if the latest leakdown numbers were done with a cold or warmed-up engine ... numbers from a cold engine are not very useful, either compression or leakdown! You also need to know where the leak could be heard in the bad cylinders ... intake snorkle, exhaust, or breather hose at the oil tank filler spout???

This may seem like beating a dead horse, but if you are truly interested in this car ... I suggest another compression and leakdown test after a minimum of a 30-minute drive to warm the engine up. Be certain that the leakage source is listened for and noted during the test on all cylinders!

[sjf911]

930-103-963-00 rings are Mahle replacements. 930-103-967-00 would be the KS replacement.

[BK911]

Maybe the compression test was done without opening the throttle. That could explain the low numbers.

[psjoe]

Thanks for all the replies

sjf911-
RE: the ring set. Could this be the issue??? Educate me. Car is a 1978.

The invoice shows this set:
930-103-986-00-M42
Piston Ring Set, sold per each cylinder, (95mm-1.5 X 1.75 X 3.5mm), 911 3.0 (1980-83), 911 3.2 (1984-89)

Should have been this set:
930-103-963-00-M42
Piston Ring Set, sold per each cylinder, (95mm-1.5 X 1.75 X 4.0mm), 911 3.0 (1978-79)

Thanks -Joe

[sjf911]

It looks like they used the rings for the later Mahle P/C setup (80-89 3.0-3.2). I assume this means the oil rings are the wrong size and may effect oiling and durability. The earlier piston would have an oil ring land for a 4mm thick ring. It appears that a 3.5mm oil ring was used instead.

[psjoe]

related post about the oil control rings over on the engine rebuilding forum:

3.5mm Oil ring in 78 SC should have been a 4.0mm?