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LOSS OF OIL PRESSURE

 
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Gatornapper  



Joined: 23 Oct 2021
Posts: 294
Location: VA

PostPosted: Tue Apr 26, 2022 10:54 am    Post subject: LOSS OF OIL PRESSURE Reply with quote

My 931 runs like new, not one complaint. Handles like new as well with new Koni Sport Shocks and tower bushings up front.

For first time coming home from car show in Williamsburg Sat. on interstate I noticed my normal hot oil pressure of 4.5 Bar at 3,000 rpm was now about 3 Bar.

Up until this weekend, idle hot pressure was 3 Bar - now it is just over 2 Bar.

I revved to 5500 rpm and still at a hair over 3 Bar. It used to be 6. Yes, oil is on full mark.

Haynes says 5 to 7 Bar.

Oil & filter are Valvoline VR-1 20W50 with about 2,000 miles on them.

What happened?

Very concerned about blowing engine, turbo, or both with such low oil pressure.

Would greatly appreciate feedback on what you experts think is going on.

Is this an indicator of main bearing issues?

Car has about 60,000 original miles on it.

TIA,

GN
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'87 944 S, looks & runs like new - sold my sweet 931; '76 914 2.0 mostly restored; 2011 Porsche Cayman S in Meteor Grey, 3.4L, Softronics ECU tune 355+hp , PDK w/Sport Chrono. Got this thing for Porsche's.......
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Gatornapper  



Joined: 23 Oct 2021
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PostPosted: Tue Apr 26, 2022 11:48 am    Post subject: Reply with quote

Shoulda read this before my post - pretty much answers my questions:

From near bottom of this page:

http://www.924.org/techsection/GarageFAQ.htm

Oil pressure - acceptable levels, common problems

What is acceptable oil pressure for the 924? According to Porsche, as written in the owners' manual (MY '77.5), "At 80 to 100 deg C oil temperature and 5500RPM, the pressure should be not less than 7kp/cm^2. A slight drop in oil pressure is normal under certain operating conditions such as prolonged highway driving in hot weather. At idle speed, with the engine oil hot, it is permissible for the red warning light to light up - this does not indicate any loss of engine reliability."

So, don't be alarmed if you see the red oil light come on at idle after pulling off the highway and sitting at a stoplight. Just blip the throttle, the light should go out and pressure come up. Just as long as it doesn't come on while you are actually driving the car with the revs up. By the way, the above pressure corresponds to about 5 bar; some early cars have oil pressure gauges that read in kp/cm^2 rather than the more common bar.

However, running with low oil pressure is not a particularly nice thing to be aware of. So, what can be done to help the oil pressure when hot? First and easiest thing to do is to change to synthetic oil and OEM filter, which will tolerate the heat much better without as much reduction in viscosity (and corresponding drop in pressure). Synthetic is even more desirable for turbos, as the heat tolerance is even more important for oil passing through the turbocharger. More about that later. The high-quality filter is a better design and higher quality than most aftermarket filters found on the shelf, and will help more in the area of reliability, not to mention preventing bursting on cold-starts when oil pressure is its highest. OEM filters also incorporate the factory-intended anti-drainback valve, while not all aftermarket filters do. This prevents oil from draining back into the block when the engine is shut off, reducing the chance of the engine running without oil pressure immediately after starting (before the oil pump has had a chance to catch up).

Next big thing, but a major investment and amount of work, is to install an oil cooler. This will help tremendously with keeping oil temps down. When used with synthetic oil and on an engine with a properly-functioning cooling system, the red oil light will never go on, even at the end of a race on a hot day. Method of installation is up to the owner, but here's one installation on a full-race 924 with a remote filter mounting. One more note on installing oil coolers; if a sandwich plate is used under the filter to add oil lines, a shorter filter must be used; the stock size filter will not clear the exhaust manifold. See the Parts page for details on which filter to use. 931's come with an oil cooler installation, to handle the additional heat produced by the turbo, so any changes here would be upgrading to a larger cooler. However, heat-soak oil pressure problems tend to be an issue on the 924, not the 931.

There are a few more things that can be done to help with oil pressure, and they will be explained in increasing order of cost. The first thing to do is to check the wiring for the oil pressure gauge; this can sometimes have problems which can result in a bad reading. The gauge panel in which the oil pressure gauge is mounted doesn't usually have the best ground, and adding an additional ground wire (from the existing ground at the gauges straight up to the stud in the firewall, behind the center speaker/grille, which holds the dash on) can often help, not only with oil pressure but also other gauge readings and with the bulb brightness (which is usually a problem). Secondly, visually inspect the wire going to the oil pressure sender to ensure no breaks or weakpoints in the wire or insulation. These can often throw off the reading.

Next item is the cam oiler tube and elbow. This applies to both the 924 and 931 (not the 924S). This is under the camshaft cover, and only requires that the cam cover be removed for access. This is well within the realm of the amateur mechanic. There is a hollow metal tube with holes along its length, which runs just over the camshaft, and provides oil to the cam lobes and lifters. It is essential that this be delivering oil properly, or the cam and lifters can end up being destroyed. Unfortunately, at the supply end of the tube, there is a plastic elbow which connects the tube to the first cam bearing cap which often breaks. When it does, it reduces the oil available to the cam oiler tube, and also results in a loss of oil pressure as seen at the oil pressure gauge. This part, #052 115 707, is readily available from the dealer, and should only cost a few dollars (same part # for 924 and 931). To install, remove the cam oiler tube by removing the two cam bearing cap nuts by which it is held, then remove the plastic elbow from the oiler tube (and any remains from the first cam bearing cap). Simply slide on the new elbow, carefully but firmly press the elbow back into the cam bearing cap, and reattach the oiler tube with the nuts. Make sure to press the elbow all the way in to the bearing cap for a good seal, but make sure it's straight or it'll break while pressing it in.

Then the oil pressure relief valve piston and spring should be replaced. These are part numbers 068 115 421 (spring) 056 115 411A (piston) and N 043 815 2 (sealing ring 20x24mm) (same part #'s for 924 (non -S) and 931). Only one of each is required for each car. Parts cost should be around $6USD - still pretty cheap. These parts are also easy to access, no more difficult than the above job with the cam oiler tube elbow. Locate the oil pump on the front of the engine. This is the aluminum casting behind the crank pulley. On the left side of the oil pump (looking at the front of the engine) will be a large bolt, with a 17mm hex head on it. Remove the bolt, catching the small amount of oil that drains out (less than 1/4qt.). You will see that it is a hollow bolt with a piston and spring inside it. Replace the piston and spring with the new ones, making sure the piston moves freely in the bore of the hollow bolt, without binding. Reinstall the hollow bolt with a new sealing ring. The piston you've replaced often sticks when old, and this can cause low oil pressure or unusual fluctuations in oil pressure reading.

Finally, if and only if the above measures have not helped, you may consider replacing the oil pressure sender. This is much more expensive, around $80USD, and hard to get to, as it is located at the back of the cylinder head. The part number is 047 919 561, for both the 924 and 931 (not 924S). R+R is straightforward though physically challenging, just remove the electrical connectors, unscrew the sender, screw in the new one, and reconnect the connectors. More expensive than the previous steps, but still less than a rebuild.
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'87 944 S, looks & runs like new - sold my sweet 931; '76 914 2.0 mostly restored; 2011 Porsche Cayman S in Meteor Grey, 3.4L, Softronics ECU tune 355+hp , PDK w/Sport Chrono. Got this thing for Porsche's.......
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Cedric  



Joined: 27 Aug 2004
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PostPosted: Tue Apr 26, 2022 4:02 pm    Post subject: Reply with quote

Be sure to double check the wiring to the guage, it can sometimes be a bit troublesome and cause false readings.

The oil pressure relief valve spring is the same as VW uses, costs almost nothing. I just changed mine because the engine is apart, and the old one had settled a bit compared to new.
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924RACR  



Joined: 29 Jul 2001
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PostPosted: Tue Apr 26, 2022 8:56 pm    Post subject: Reply with quote

Good point on wiring; in many old Porsches including the 924, it's common for the oil pressure and fuel gauges to read a tick lower, and the water temp to read a tick higher, when the headlights are on.

Despite their reputation (vs. British cars), Porsche wasn't the greatest at designing the electrical systems. There's even a story about the race team chasing a small but persistent oil pressure drop all night at LeMans in a 917... only to have it mysteriously disappear when the sun came up...
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Gatornapper  



Joined: 23 Oct 2021
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Location: VA

PostPosted: Tue Apr 26, 2022 9:50 pm    Post subject: Reply with quote

Thanks Cedric and Vaughan -

An electrical connection makes sense as it seemed to come on suddenly - will pursue that first after changing oil and filter....and going with OEM filter.

But before this weekend, it's always been 4 to 6 Bar, maybe 7 when cold.

Is that acceptable?

Thanks!
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'87 944 S, looks & runs like new - sold my sweet 931; '76 914 2.0 mostly restored; 2011 Porsche Cayman S in Meteor Grey, 3.4L, Softronics ECU tune 355+hp , PDK w/Sport Chrono. Got this thing for Porsche's.......
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Cedric  



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PostPosted: Tue Apr 26, 2022 10:34 pm    Post subject: Reply with quote

With hot oil it should have 6bar above 5000rpm according to the book.

I have had lots of issues with the multi connector behind the guage cluster, which made my oil pressure have its own life. And the classic mentioned above that the oil pressure and coolant needle moves when the lights are put on
The car has uncovered spade connectors everywhere, its bound to work like crap after 40 years, and the connectors arent exactly great with modern standards. I still cant trust my oil pressure guage, even though the sender is new and i tried fixing the cables and connectors, also tried two different guages.
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Gatornapper  



Joined: 23 Oct 2021
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Location: VA

PostPosted: Wed Apr 27, 2022 8:12 am    Post subject: Reply with quote

I used to have 6 Bar at below 5 grand - and the drop was so sudden, I'm wondering what happened.

Hoping it's just a connection.....and one I can easily get to.

GN

Cedric wrote:
With hot oil it should have 6bar above 5000rpm according to the book.

I have had lots of issues with the multi connector behind the guage cluster, which made my oil pressure have its own life. And the classic mentioned above that the oil pressure and coolant needle moves when the lights are put on
The car has uncovered spade connectors everywhere, its bound to work like crap after 40 years, and the connectors arent exactly great with modern standards. I still cant trust my oil pressure guage, even though the sender is new and i tried fixing the cables and connectors, also tried two different guages.

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'87 944 S, looks & runs like new - sold my sweet 931; '76 914 2.0 mostly restored; 2011 Porsche Cayman S in Meteor Grey, 3.4L, Softronics ECU tune 355+hp , PDK w/Sport Chrono. Got this thing for Porsche's.......
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Gatornapper  



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PostPosted: Wed Apr 27, 2022 10:40 am    Post subject: Reply with quote

There was resistance in the ground wire, so ran new #14 stranded wire from frame ground to ground wire to oil pressure gauge (big enough? ).

And of course, pressure increased some, but not as much as I hoped. Cold idle is now 4.5 Bar, and barely warm engine at 5,000 rpm is just over 5.5 Bar.

New fully synthetic 20W50 and OEM filter going in tomorrow or Thur. Will then check pressures with hot engine.

I'd still like to see 7 Bar at 5,500 rpm...........

GN
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'87 944 S, looks & runs like new - sold my sweet 931; '76 914 2.0 mostly restored; 2011 Porsche Cayman S in Meteor Grey, 3.4L, Softronics ECU tune 355+hp , PDK w/Sport Chrono. Got this thing for Porsche's.......
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924RACR  



Joined: 29 Jul 2001
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PostPosted: Wed Apr 27, 2022 9:50 pm    Post subject: Reply with quote

I actually wouldn't even want 7 bar except when cold.

5.5 bar up high, on a not-new motor, sounds perfectly fine to me.

14ga wire is indeed overkill for the sender, though not massively so - for sure, I'd leave it in there if I were you - just make sure it's sealed against water!
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Gatornapper  



Joined: 23 Oct 2021
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PostPosted: Thu Apr 28, 2022 11:49 am    Post subject: Reply with quote

Vaughan -

Thank you - making me feel much better. From the time I got the engine running I noticed how great the oil pressure was - and that's why I became very concerned when it recently dropped significantly. I'm especially concerned knowing how that turbo needs tons of oil.

Good reason for #14: I had spool of green laying around and only other green (don't have brown) I have is 22 ga. I needed to fish the wire a good 2' in a very narrow passage so a stiff wire made that easy. Being oversized will ensure very low resistance - at terminations. Will be essentially none over wire itself.

Wire also "re-grounds" all other devices on same brown ground wire in area of center gauges & lights.....multi-purpose.

Didn't get to the oil & filter change today so looking forward to see what that does tomorrow.

BTW - another factor on engine that is a good indicator: it runs very cool. If car is moving, almost always in 1/3 mark on gauge. On hot day never gets over half-way mark. I did new water pump, thermostat, belts, coolant, etc. so cool temps are not unexpected. And cool engine means cool oil. My oil cooler is nice and clean too.

Only time engine temp goes above half-way mark is when engine is hot, outside is hot and car is stopped and idling.

GN

924RACR wrote:
I actually wouldn't even want 7 bar except when cold.

5.5 bar up high, on a not-new motor, sounds perfectly fine to me.

14ga wire is indeed overkill for the sender, though not massively so - for sure, I'd leave it in there if I were you - just make sure it's sealed against water!

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'87 944 S, looks & runs like new - sold my sweet 931; '76 914 2.0 mostly restored; 2011 Porsche Cayman S in Meteor Grey, 3.4L, Softronics ECU tune 355+hp , PDK w/Sport Chrono. Got this thing for Porsche's.......
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Gatornapper  



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PostPosted: Fri Apr 29, 2022 10:55 pm    Post subject: Good News! Reply with quote

5 qts. of synthetic VR-1 20W50 yesterday did the trick.

Hot engine = 4 Bar at idle, 5 Bar at 3,000 rpm, 6 Bar at 5,000 rpm.

So relieved my sweet 931 has an engine that is internally tight.

A few small oil drops I have yet to locate and fix, but very minor. One driping onto starter seems like origin is rear main seal......fortunately is just a drip or two a day.

GN
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'87 944 S, looks & runs like new - sold my sweet 931; '76 914 2.0 mostly restored; 2011 Porsche Cayman S in Meteor Grey, 3.4L, Softronics ECU tune 355+hp , PDK w/Sport Chrono. Got this thing for Porsche's.......
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924RACR  



Joined: 29 Jul 2001
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PostPosted: Sat Apr 30, 2022 8:48 pm    Post subject: Re: Good News! Reply with quote

Gatornapper wrote:

A few small oil drops I have yet to locate and fix, but very minor. One driping onto starter seems like origin is rear main seal......fortunately is just a drip or two a day.

GN


That's possible, but look first for leaks up top at the back of the head, like the distributor - entirely possible and not uncommon.
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MikeJinCO  



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PostPosted: Sun May 01, 2022 12:55 am    Post subject: Reply with quote

Vaughan

Do you have a PN or more info for that VW oil pressure spring?
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Gatornapper  



Joined: 23 Oct 2021
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PostPosted: Sun May 01, 2022 3:23 am    Post subject: Re: Good News! Reply with quote

Vaughan -

As always, thanks for the tip. Will do.

While I'm on top, a tiny bit of oil is found on top of intake manifold. Where would that be coming from?

GN


924RACR wrote:
Gatornapper wrote:

A few small oil drops I have yet to locate and fix, but very minor. One driping onto starter seems like origin is rear main seal......fortunately is just a drip or two a day.

GN


That's possible, but look first for leaks up top at the back of the head, like the distributor - entirely possible and not uncommon.

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'87 944 S, looks & runs like new - sold my sweet 931; '76 914 2.0 mostly restored; 2011 Porsche Cayman S in Meteor Grey, 3.4L, Softronics ECU tune 355+hp , PDK w/Sport Chrono. Got this thing for Porsche's.......
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Cedric  



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PostPosted: Sun May 01, 2022 3:29 am    Post subject: Reply with quote

MikeJinCO wrote:
Vaughan

Do you have a PN or more info for that VW oil pressure spring?


https://www.ebay.com/itm/194896649716

This is the one i bought, came in a vw orignal parts bag. I did some interesting measurements of spring rate and seat pressure with the new spring vs 2 different old ones. When im through my ferocious man cold i will do a post with the numbers.
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