930 low oil pressure problem

[28rusblue]

Hi,

I have a 1978 930 Turbo which was rebuilt in 1996 about 46,000km ago by a previous owner who ran the car low on oil due to oil leaks .... expensive mistake!

One advantage of living in Australia is original 930 cars are pretty rare, so it was easy to tracked down the mechanics who have worked on the car from 1992 -2005 to confirm the rebuild with at least a rebuilt crank, new bearings, oil pump, turbo rebuild, new pistons and barrels and rings.

The issue is, the darn oil pressure is very low when the car is warm! I have already tried replacing the oil return valve & spring.

The engine seems fine, no noises, good compression, good leak down test results, no bad oil leaks, use about a litre of oil every 1000km,

The leak down is 3% on all cylinders except one which is 6% And a compression test came up at a pretty even 150psi at less than 500ft above sea level.

The engine blows no smoke and only occasionally a puff of smoke on start-up.

Engine leaks no oil and engine PPM is normal. Co2 is always little higher than in the spec book. Not sure if that is relevant.

We have checked the oil pressure gauge and put a pressure meter on the car and the oil pressure is nearly as low as the car's dash gauge suggests.

Warm oil at idle Oil Pressure is 0.25 to 0.5 bar. The oil pressure idiot warning light has never come on and engine has no noises not even a rocker noise at either cold or hot.

Oil Pressure when driving

1bar at 2000RPM
2bar at 3000RPM
3 Bar at 4000RPM

after 4000rpm, the oil pressure never goes much beyond 3bar

My mechanics is very concerned about the low pressure and whether the piston squirters are working properly and thinks maybe we need to start considering pulling the engine down as maybe they forgot to put in the little rubber hose in the oil main gallery or something like that when it was rebuilt? Or maybe the pump is slowly failing...who knows..


Do I rebuild it or keep driving it? The Oil Pressure does not seem to be getting any worst... I worried about opening up a can of expensive worms.... I'm also a little concerned with the crank being rebuilt once, I might run into trouble finding a set of new bearings for it once we have it all pull it down.

Can I run heavier weight oil like a Penrite HPR 30 or even go the HPR 40? (I ever only run mineral oil) or could a heavy oil damage my engine even more?

I'm running out of ideas and options and would be interested in a few second opinions.

Thanks in advance,
Greg

[Flieger]

The pressure sounds alright to me. I use Brad Penn 20W50 in my 2.7RS spec motor. The pressure is usually a little over 10 pounds per square inch (psi) per 1000rpm. Since 1 Bar is 14.7 psi, your pressures fall into the generally accepted (in the US) "proper" range of 10-15 psi per 1000rpm. I do not think you really have much to worry about. What oil are you running now? What is your oil pressure like?

[bpu699]

Put in cam line restrictors, should boost pressure by 0.5 bar...cheap to do.

20/50 weight oil helps....

My oil pressure peaks at 4 bar or so, plateaus at 3500rpm or so...seems adequate. Fabulous leakdowns like your, lots of motor work by PO. Shimming the pressure releases did nothing... Consensus on this board was that its ok...

It seems that in a turbo a lot of the oil and pressure is diverted to cool/oil the turbo. I always wondered if variances in your turbo/modifications could lower pressure? The oil supply via the cam restrictors is TINY, wheras the oil supply line to the turbo is rather large...

Ripping open the motor is a huge financial feat... I hope you don't have to do it. Good luck!

Bo

[Steve@Rennsport]

Hi Greg,

As you can imagine, these issues can be tough to troubleshoot from afar,.....

The 1 bar/thousand RPM rule is the guideline for sufficient oil pressure. Variables such as oil viscosity and bearing clearances both play major roles in what each engine actually sees.

If I had an engine with 3 bar at 6K, I'd be inclined to take it apart far enough to pull a few rods and measure bearing clearances, especially when you don't have much detailed history. I think your mechanics are offering sound advice as its far better to be safe than sorry, given the consequences of a rod bearing failure.

JMHO, but switching to a heavier oil will not help in this situation.

[28rusblue]

Thanks Guys

bpu699- if I put in cam restrictors in won't that rob the top end of oil?

Thanks Steve,
That's sort of, what my mechanic is saying, but he hopes it is the oil pump rather than excessive bearing clearances and a crank that needs work. There are no noises in the engine. It does run a little hotter than other 930s he works on which is another reason he is concern with the low oil pressure on an oil cooled car.


If I do rebuild what are others doing with bearings and Cranks?

What’s the story with 930 main bearings availability?

My mechanic is a little worried if we rip her apart we might run into big trouble finding a full set of suitable bearings or a rebuild-able crank. The crank has already been rebuilt once.

The shop I take my car to had one 930 car in the shop for three months, had trouble finding a either a rebuild-able replacement crank or a full set of suitable undersize bearings. I think they had major issues finding the number 8 nose bearing.

Can't they machine the crank to suit bearings from a different car or a later model 964 or something? As I notice no 8 nose bearings and even .5 undersize bearings are available for a 964 3.3 turbo.

What is the difference in the cranks and or blocks between a 964 and a 930? I thought they are much the same

Thanks,
Greg

[turbobrat930]

Just for FYI..... I had spun # 2 and # 5 rod bearings in my car a few years back. I not only damaged my rods, but my crank was trashed as well. I brought my engine to JB Racing in Talavaras, FL and had them do a few mods.

One of the mods was to send my crank off to CCR ( Custom Crankshaft Repair) in CA. Since my crank needed to be fixed anyways, I had Armundo at CCR offset grind my crank. It is now stroked to 78.8mm and uses custom Pauter rods with the Nascar Chevy 2" bearings. I also had the center oil mods done to the crank... all this work was around $2000.00 ( the rods were not included in this price). The crank came back looking like jewelry!!! Coupled with 98mm P&C's I now have just under a 3.6L displacement!

Not saying this is the route you need or will take... just another option.... If you want further details, you can PM me and I will give you further info

[Steve@Rennsport]

Originally Posted by 28rusblue

Thanks Guys

bpu699- if I put in cam restrictors in won't that rob the top end of oil?

I'm not a fan of using those things as the top end of the engine is the hottest part and needs all the cooling and lubrication it can get. This is a complex subject,.....

Thanks Steve,
That's sort of, what my mechanic is saying, but he hopes it is the oil pump rather than excessive bearing clearances and a crank that needs work. There are no noises in the engine. It does run a little hotter than other 930s he works on which is another reason he is concern with the low oil pressure on an oil cooled car.

If the pump was subjected to swallowing some trash, such as after engine failure, its should be opened up and closely inspected.

If I do rebuild what are others doing with bearings and Cranks?

We use stock cranks after magnaflux, cleaning, balancing, and micropolish.

What’s the story with 930 main bearings availability?

No problem for standard mains. We never use Glyco rod bearings anymore in these, instead we use aftermarket ones.

My mechanic is a little worried if we rip her apart we might run into big trouble finding a full set of suitable bearings or a rebuild-able crank. The crank has already been rebuilt once.

If its been turned more than .025mm, bearing availability may be tough. I'd suspect it may have been turned slightly undersize which will cause your oil pressure problem. Time for another good used standard one. Personally, I wouldn't use it anymore.

The shop I take my car to had one 930 car in the shop for three months, had trouble finding a either a rebuild-able replacement crank or a full set of suitable undersize bearings. I think they had major issues finding the number 8 nose bearing.

Can't they machine the crank to suit bearings from a different car or a later model 964 or something? As I notice no 8 nose bearings and even .5 undersize bearings are available for a 964 3.3 turbo.

Undersize bearing availability has been a hit or miss affair for some time. JMHO, but you REALLY don't want to use such a crank and especially if it wasn't rehardened and straightened after machining.

What is the difference in the cranks and or blocks between a 964 and a 930? I thought they are much the same.

Big differences in 964 and 930 cases,.......3.3 Turbo cranks are all very close cand compatible.

[28rusblue]

Thanks Steve,

Any suggestions on what to pay and where to buy?

What sort of money is a used crank over there, can you negotiate getting them sent to a shop and checked X-rayed before parting with all my hard earned.

Otherwise I'm guessing it's pretty risky buying one, could be more stuffed than mine.

Greg

[Eagledriver]

Have you confirmed the low pressure, could be just a guage/sender problem. Cam restrictors are an easy fix and perfect for your situation. They have been used on many engines with no ill effects. Still plenty of oil for the cams and valves. Lots of threads on here to read about cam oil restrictors. I don't use them because I have too much pressure when they are installed, but I'd not hesitate to use them if I had low pressure.

-Andy

[28rusblue]

Hi Andy,

Yes, have already tested the oil pressure on the car and check the pressure at idle, 2000rpm, 3000rpm & 4000rpm and found the pressure gauge in the dash to be pretty accurate. The rebuild suggestion is the last resort as we have run out of ideas everything else is really good on the engine...... just the darn oil pressure is low...

[Steve@Rennsport]

Originally Posted by 28rusblue

Thanks Steve,

Any suggestions on what to pay and where to buy?

What sort of money is a used crank over there, can you negotiate getting them sent to a shop and checked X-rayed before parting with all my hard earned.

Otherwise I'm guessing it's pretty risky buying one, could be more stuffed than mine.

Greg

My pleasure, anytime.

Send me an e-mail and I'll do some digging to find a good used std crank and I can magnaflux that for you, if you wish.

[Flieger]

The oil line restrictors may raise the pressure reading on the gauge but they do not fix any of the real issues you may have- worn oil pump or a bad crank. I do not like the idea of restricting oil to the high-stress valvetrain area.

[28rusblue]

Yeah...... I think if I can find the money and a crank, I should rebuild and fix the problem before I do some real damage... rather than just do a cover-up with oil restrictors, a turbo needs all the cooling up top it can get...

Steve, I just sent you an email to the porsche@rennsportsystems.com address on your post

Thanks guys, I think I'll go find a six pack and go sit in my car...... depressing... just got her running nice, just fitted a set of Brian's headers too...now she will be off the road again for months... bloody frustrating things aren't they...

[calling911]

You should give the car to me.. it wouldnt be idling much.. cheap repair

[28rusblue]

Thanks Calling 911,

Not sure you would want it in the US as someone put the steering wheel on the wrong side, so Porsche thought they had better send it off 'downunder' to Australia....

[Flieger]

That would be great for Willow Springs Raceway- it is a proper, clockwise lap. It would also be great for the twisty canyon roads around here since there seems to be a predominance of right turns, or at least those are the only turns you can "apex" while still in your lane.

[calling911]

Originally Posted by 28rusblue

Thanks Calling 911,

Not sure you would want it in the US as someone put the steering wheel on the wrong side, so Porsche thought they had better send it off 'downunder' to Australia....

You let me worry about that nasty ole steering wheel...

Seriously, Im very sorry for your troubles.. Id recommend you check your gauge and make sure its correct.

[lindemans]

In my view one needs to be careful with measures re low oil pressure.

Key is that adequate flow of oil is obtained by a minimum required oil pressure to "fight" the flow-resistance of the oil circuit created by small oil passages and bearing clearences.

If engine parts are within spec, flow-resistance creates build up of oil pressure and associated oil flow as per the engine design. These factors cannot be looked at in isolation. If you restrict the oilflow in the system, the oil pressure will rise but the flow will be reduced at the same time, destroying the design balance.

In other words: low oil pressure is a sign of an issue in the engine; but artificial measures to increase the oil pressure are merely cosmetic to get the gauge readings to the desired level, not the solution to the root problem.

In the extreme case entirely blocking the oil flow will yield the highest oil pressure possible on the gauge, but no flow to lubricate and cool the engine ...