Is this 930 engine stuffed? Need guru input...

[iswinkels]

Hi All,

My expertise is in VW engnes(high performance and turbo), not porsches but ive been asked to provide some technical assistance with a 930 project.

Ive spotted an oil leak that concerns me. At idle the engine is fine, but if i rev the engine a few times while looking around the crankshaft pully area i see oil bubbling out from between the crankcase and some other round alloy part that is probably carrying the pully end crankshaft seal. See attached picture.



A little history... It was rebuilt not all that long ago and is only just run in. The engine has been over filled with oil once before, and the ignition was also too far advanced because the distributor was installed 1 tooth out.

Idling at 1000 rpm the oIl pressure is also a little low for my liking too. I have heard this is not abnormal for some 911 engines, and it does get pressure the moment the revs are above 1000 rpm so oil is circulating and its not knocking at idle. Is there much truth to this?

If I had to guess i'd suspect there may be damaged ring lands on the pistons. It doesnt seem to be burning oil though, and there is nearly no pressure of airflow from the crankcase breather when its reved.

Ive also just noticed the oil level is about 15mm above the full line as well, so could this explain it?

I am wondering if the oil leak and crank case pressurizing is due to the breather line from the crankcase to the catch being too small?

So... next step should be a compression test i guess?...

I appreciate hearing everyone's thoughts.

[euro911sc]

That might be the end of the crank bearing #8 you are seeing:



The Crank Bearing will stick out on that end. It may be that you have a failing o-ring (that orange thing ) or if it was recently built, a forgotten o-ring. I almost forgot mine...

Only solution would be a complete tear down/re-seal. I think there is a thread on this kind of leak and the many failed attempts to fix it w/o splitting the case... lots of gruesome RTV pictures

Best regards,

Michael

[euro911sc]

PS: take it back to the builder If that was your friend, well, not much to do there. I don't think you have a ring problem w/ no pressure coming out of the breather hose and the dia. of that hose is fine. It should go back to the oil tank from the breather cover... at least that is the path on my NA 3.0l w/ the same CIS system (my assumption is no EFI/Carb conversion).

If you over fill the oil you get oil in the air box and lots of smoke. So if you are not smoking like a dance floor then you are fine. You can always drain some out if you are worried

If you are still in break-in and the rings have not seated your compression test results may be suspect.

Best of luck!

-Michael

[ischmitz]

Well, the oil leak seems to be coming from the #8 nose bearing. While not perfect this alone is no reason to think the engine has permanent damage. It is an inconvenience. Mine on the 3.6 is leaking a bit and I get about one drop over a couple of days on the floor when the car sits for days. Oh well...

The advance is another concern. If the engine ran too long with too much advance this can lead to all sorts of damage (ring lands, rod bearings, etc.) It is hard to say without actually taking a look inside.

What makes me wonder is that when rev the engine the crank case pressure gets up leading to the bubbling at the #8 bearing. Since you are not making any boost when reving the engine there shouldn't be substantial pressure buildup in the crankcase pushing oil out of the seals.

Maybe the rings have not seated properly or there is in fact damage to the rings or ring lands. Any chance the breather is clogged. You say there is hardly any airfow when reving but you do get crankcase pressure. How do you determine that? With the breather hose disconnected at the catch it should vent the crankcase and the bubbling at #8 should stop.

Ingo

[euro911sc]

Originally Posted by ischmitz

Well, the oil leak seems to be coming from the #8 nose bearing. While not perfect this alone is no reason to think the engine has permanent damage. It is an inconvenience. Mine on the 3.6 is leaking a bit and I get about one drop over a couple of days on the floor when the car sits for days. Oh well...

+1 if it is not just spewing oil. would need to check it after a drive and try and determine just what the leak rate is. If it is just dripping no big deal, but if you can measure it over the course of a short time... well he has something to fix.

Originally Posted by ischmitz

What makes me wonder is that when rev the engine the crank case pressure gets up leading to the bubbling at the #8 bearing. Since you are not making any boost when reving the engine there shouldn't be substantial pressure buildup in the crankcase pushing oil out of the seals.

Maybe the rings have not seated properly or there is in fact damage to the rings or ring lands. Any chance the breather is clogged. You say there is hardly any airfow when reving but you do get crankcase pressure. How do you determine that? With the breather hose disconnected at the catch it should vent the crankcase and the bubbling at #8 should stop.

Ingo

I think it is an oil pressure related leak and not related to case pressure. If you rev w/ no load the pressure still goes up in line with the revs and the oil will be pushed out the nose bearing... but not necessarily where he may be seeing it so maybe I'm incorrect. *shrug* Do as Ingo instructs and pull the case breather hose and see if the bubbling stops.

Best regards,

Michael

[ischmitz]

Michael, good points. In my case the leak shows when the car sits for several days. I assume it's oil collecting in the sump. Once it reaches the lower edge of the nose bearing it starts seeping through the seam between the nose bearing and the case.

If his leak is through the bearing surfaces and gets worse when the oil pressure goes up that is another story...... Still, I wonder where the bubbles come from. That indicates air being pushed out there as well.

Ingo

[spuggy]

Originally Posted by iswinkels

and the ignition was also too far advanced because the distributor was installed 1 tooth out.

That can be really bad for a 930 because of detonation. Mind you, it'll run really, really, sharp off-boost...

As it's just been run-in, hopefully it won't have seen much prolonged boost and that may just have been a very good save on your part.

Idling at 1000 rpm the oIl pressure is also a little low for my liking too. I have heard this is not abnormal for some 911 engines, and it does get pressure the moment the revs are above 1000 rpm so oil is circulating and its not knocking at idle. Is there much truth to this?

Early 911's - like 60's or 70's 2.0's and 2.2's are noted for having low oil pressure at idle (to the point where the oil pressure warning light comes on).

All 76-89 N/A cars have the same oil pumps, and they aren't.

A 930 is not an N/A 911 and they have huge oil pumps.

930 oil pump flows 100 liters of oil per minute at full chat, according to this thread: Oil Pump Rating

My 930 motor reads 20-25 PSI at idle with the oil hot and hits full pressure (75 PSI, or 5 bar) long, long before the factory minimum spec of 5,000... I can pick up 5-10 PSI by raising idle ~200 RPM on the pedal.

If yours is reading 15 PSI (1 bar) or less at idle, I think it'd be cause for concern on a 3.2 (which has a much smaller oil pump), much less a 930.

If I had to guess i'd suspect there may be damaged ring lands on the pistons. It doesnt seem to be burning oil though, and there is nearly no pressure of airflow from the crankcase breather when its reved.

Ive also just noticed the oil level is about 15mm above the full line as well, so could this explain it?

Nope, that'd just make it smoke if the excess dumped to the airbox. I think my crankcase breather goes to the oil tank, but I won't swear to it..

So... next step should be a compression test i guess?...

One of the first evidence of detonation on a 930 (overboost, timing too advanced or too lean) can be the amazing 500-piece piston rings...

Often, owners have absolutely no idea as the car seemed to be running great...