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Discussion summary
YOUR RESEARCHlow oil pressure at idle
Reported or suspected cause
variocam solenoid/actuator was acting up
Reported cause
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Reported cause
The only time I had any problem with a variable idle was with my Boxster when what proved to be a VarioCam solenoid/actuator was acting up.
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Performed · outcome unconfirmed · Original poster
Have a new one in there right now that is OEM installed by Porsche when they did the AOS.
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Performed · outcome unconfirmed
Installed a manual fan switch for the front radiators to turn on high speed circuit (Helps, again by lowering temps)
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Suggestion
It all boils down to ensuring the idle speed is in spec and then checking the oil pressure to verify the oil pressure sensor in the engine is working properly.
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We have a 1999 996 C4 tiptronic. AOS has been replaced last year.
Just noticed a few days ago while driving in congested traffic, the temp gauge reading was reaching to 90 Celsius. At idle, the
oil pressure
guage was as low as 0.5 Bar. Oil in the car is 0-W-40 and the oil change was done by Porsche, and the temperature outside was 20 Celsius. Wife reported that she felt at idle there was a moment the car felt like it wanted to stall, but was idling at 500 ish.
I checked it out today. Temp is 15 Celsius. Idle was 850 ish rpm. Pressure started at 5 Bar as usual. Drove around and all seemed fine, as the pressure settled to 2 - 3 and 1 Bar at idle. As car got hotter and it climbed to 90 Celsius, oil pressure dipped to below 1 Bar, even to half. Oil light flashed for a split second, but did not hear any knock or anything. Turned on the A/C to get the fans going, in case it was that. and temp dropped and oil pressure went back to 1 Bar. Concerned, as it is not hot out right now.
Before I get the comment "do a search" I have. This is what I have found:
get the actual pressure tested to make sure the gauge is accurate. I will, but wonder as at low idle and low oil pressure, there was knock, although momentary?
Could be the sensor is out - cheap to replace
The pressure relief spring that broke in half for the sending unit
If the fans, get the low temp thermostat. Have a new one in there right now that is OEM installed by Porsche when they did the AOS.
Go to a heavier oil.
or finally, engine is about to blow up and run away...
The threads I was looking at wereod, so any new ideas would be nice. Car is parked until we get it looked at or we solve it ourselves.
Thinking of installing a manual
switch
to turn on the fans front and back, if that is the issue. But 90 Celsius still seems withing normal ...
My car pegs 5 or above 5 when cold, so if you are already just below 5 at cold start, you are going to be down 1/2-point tI begins with. The gauge could be off, or the sender could be off.
If you are idling at 500, that�s the cause of the problem. Idle should be a minim or 650 or 675, I cannot remember which. With the AC button depressed, I think it will run at 750-800 RPM.
You need to have the oil pressure tested by a real gauge. You may need to replace the filter bypass and oil pump bypass springs and valves. Inspect and make sure you have the proper filter. You may need to drop the sump plate and inspect the oil pickup screen to see if it�s clogged. Heavier oil will not fix any issue, but would be good as a last resort. You�ll only gain 1/4 point, but could make a blockage worse with heavier oil.
Do some direct observation rather than listening to the customer (wife) "facts" and observations. My customers (wife and kids) are not the greatest at reporing useful diagnostic information. Also, I find it worthwhile to systematically troubleshoot issues rather than guessing and throwing parts at problems. Personally, I'd start with diagnostics on the guage/sender side, verify that that is good, then move on to the pumping and pressure regulation side.
As much of a car nut as I am (and I consider myself pretty mechanically inclined) I thought my oil pressure guage was wacky too, and I even went as far as buying a new sender before going back to basics and doing more observation to see that the needle did fluctuate properly. It just spends a lot of its life north of 4 bar in normal rpm range usage.
I read that one, yes. I included the spring as a possible culprit. Haven't checked the actual pressure yet, but will on Tuesday. Seems most likely to me as well.
After that, I am thinking of going to 5 W 40 and replacing the spring. Beyond that, it will have to be Porsche .
I haven't experienced the 'feels like stalling' at idle for myself, but i have seen the low oil pressure briefly flash at 0.5 Bar and idle around 500 woth temperature around 90 Celsius.
If the idle is too low so will be the oil pressure. They go hand in hand. I would look into why the idle is so low that the engine is almost stalling before concentrating on the oil pressure.
Jim,
I started a thread 2 years ago detailing the same symptoms you have. I also have a 99 with tiptronic located in Edmonton and I've experienced the same less than 1 bar of pressure. Worse at idle in spring/summer traffic. In winter, in stop and go traffic my idle is 0.8 or 0.9 Bar and my car idles consistently at 700rpm which I believe is what the engine hood sticker states for a tiptronic
Things I checked/did:
Changed Relief Spring/Piston (Twice) (No change)
Dropped sump plate looking for clogged pickup tubes, found nothing
Took off swirl pots checking for debris, found nothing
Changed Waterpump, Thermostat, new Coolant (This helped, but only really through lowering temps)
Visual Inspection of the oil pump gears and housing while doing the water pump job, I didn't notice any damage
Installed a manual fan switch for the front radiators to turn on high speed circuit (Helps, again by lowering temps)
Basically I've found nothing wrong that is correctable, I sort of resigned myself to either it wasn't a problem or its a problem related to the main bearings or something else involving a complete teardown to find out. I've since driven 15,000 km over 2 years and nothing has changed. Hasn't gotten better or worse.
I do switch to Mobil 1 5/50 in the summer and that brings up the pressure somewhat, but it still does not idle above 1 bar when warmed up in moderate stop and go traffic. Somewhere in a Porsche manual it's stated that if you have 3.5 bar at 5k rpm that is acceptable. My car produces 4bar at 5k RPM even after sitting in 30C stop and go traffic and is idling somewhere around 0.6 or 0.7bar.
and now for something completely different.
1. Clean rads and condensers.
2. Install 160F low temp thermo(I can't tell from your statement if you have, or don't have it already)
3. Use correct oil viscosity for your car(5-40)
It appears your issue is thermal related.
YMMV, objects in mirrors, contents have settled, and may cause **** leakage
Rads I cleaned last month. No debris in there anymore. I fully intend to change to 5 W 40 asap. As for the low temp thermostat, I may, but am thinking of installing a switch to turn them on when I want.
Before you install a manual switch..........is there really a problem that you need to fix or you just think there is a problem? To me, it sounds like you are looking for a solution for a problem that doesn't exists. Is you idle too low?
Today idle was at just over 600 when fully warm. Couple times when at a stop light, it dipped to below 600 momentarily. Did read below 1 Bar and as low as 0.5 Bar. Turned on air conditioning to turn on fans. Seemed to increase pressure and idle slightly.
Got some oil and will change it out this week.
Maybe the fans is a solution to a problem that is not there, as you say. Still, I thought of doing it anyway even before this. Be really simple.
Fail to see how switching from 0w-40 to 5w-40 will make any difference in hot idle oil pressure since both oils have "40" as the high temperature/high sheer viscosity index which is measured at 212F.
0w-40 is fine. That is not the problem. (BTW, in my Dodge Hellcat in which I run a 0w-40 oil (Pennzoil) even at 230F the hot idle oil pressure only drops by around 2 or 3 psi from what it is at 212F. Roughly at 212F it is 40/41psi and at 230F it drops to 37/38psi. A bar is a bit over 14psi so a 3psi drop is just 1/4 a bar.
(When I switched from 0w-40 to 5w-50 my 996 Turbo hot idle oil pressure didn't change. The "50" is not really a thicker/heavier oil it just has a better high temperature/high sheer number.)
Low oil pressure at low idle speed -- idle speed below the norm -- is not a low oil pressure problem but a low idle speed problem. Do not know what the idle speed is for a 996 engine but you need to know. For my Boxster it was I believe 740 +/- 40 range IIRC. It is 740 +/- 40 for my 996 Turbo and this is the same for both the manual and automatic equipped cars.
You need to be sure the engine idles at the correct RPMs. Not sure why it is not idling at the right RPMs. The only time I had any problem with a variable idle was with my Boxster when what proved to be a VarioCam solenoid/actuator was acting up. I noted the idle speed would fall to around 500 and to me it felt like the engine was going to die. Had the low oil pressure warning light flashed at around 500 RPMs I would not have been surprised. Gear driven oil pumps are not very efficient at low speeds. There's a reason why the idle speed is 740 and not 700 or 660, 620, 580, etc.
Next, unless you have already done this you need to be sure of the hot idle oil pressure with a reliable/trustworthy gauge.
Also consider if you think the car is running hotter than normal , this will make the oil thinner than normal and will reduce oil pressure at idle, also as has been mentioned might be worth changing the oil pressure relief spring and piston in the oil pump when you do the oil change !
Stop throwing parts at it!
Identify the problem, be 100% sure that it IS the problem and ONLY then buy the part/s that are needed for the repair. You are going in 10 different direction all at ones, this will not end well.
Step 1: Check idle speed and go from there.
One has to be aware of what is "normal". I didn't know the oil temperature for my Boxster or Turbo engines, but in one case the Boxster coolant temperature got up to 226F. This when being driven -- in town -- in 116F ambient temperature. I expect the oil was at least that hot probably hotter.
For a loaner Macan when just being used normally as my commuter vehicle -- and certainly not in 116F ambient temperature -- the oil temperature got quite a bit hotter than 230F. While I can't recall the oil temperature now it was "way" above what I expected to see so much so I spoke with the SA and senior tech at the dealership and both told me the oil temperature I was seeing was "normal" for this vehicle.
For my Hellcat the oil temperature can reach -- this in town driving -- 230F (and I've never seen it go higher). But even with the oil temperature this high the coolant temperature is around 210F.
As I mentioned in another post, even with the oil at 230F the oil pressure drops just a few PSI from what it is at 212F. I use 212F temperature as a base line as this is the temperature at which the "40" in "0w-40" is obtained. IOWs, oil at 212F is not hot it is at its working temperature.
My point is unless the engine is running very very hot oil pressure shouldn't fall off but just a few PSI.
There is a problem replacing the oil pressure relief spring and piston. The spring may be the wrong one, it may be bad, the piston may not fit properly or may have a burr/nick and may bind.
It all boils down to ensuring the idle speed is in spec and then checking the oil pressure to verify the oil pressure sensor in the engine is working properly. If the idle speed is ok and an independent verification of the oil pressure find the pressure low at idle -- though in all the factory documentation I've seen regarding oil pressure it is called out at some elevated RPM and at some elevated temperature so I do not know what constitutes low oil pressure at hot idle (other than I guess the low oil pressure warning light flashing maybe...) -- then one can possibly consider a new oil pressure relief spring and piston.
But the problem -- if there is a problem -- can be due (for example) the pressure relief valve that controls oil supply to the piston oil jets. If this is not working properly it can fail to close when oil pressure drops below some low threshold. Normally if oil pressure drops below some threshold the valve should close thus helping to ensure sufficient oil pressure and supply to the main/rod bearings and the camshafts/lifters.
Update for those that have the same issue as me.
We replaced the oil pressure relief spring and piston. with the updated 997 piston and new spring and new crush washer. The old parts looked fine, though, and it already had the updated piston. Only lost a cup of oil. Oil looked good, and no surprises in it. Maybe the spring was weak, idk, but I doubt this will solve the problem. Was cheap to do this, so not a biggie. For others that had this problem, what did you do?
I would still take the advice already given in this thread:
1.) Make sure your engine idles at last 625RPM. Hitting the AC button should bring idle to 800. The oil pressure is directly related to engine RPM, as the oil pump is driven off the engine.
2.) Attache a certified oil pressure gauge and measure the oil pressure. Your sender or gauge might be off by only 1/4-point, which is enough to make a big enough difference.
3.) Drop the sump plate if you haven't already and inspect the oil pickup; remove any and all debris from the pickup
4.) If all else fails, and you know your engine is healthy, it just might have loose tolerance. In that case, increase your oil viscosity by switching to a 50w oil. Only do this if the cold start temps are above freezing. If you drive is freezing cold temp, I'd stick with 0-40 or 5-40 in the winter.
Also if your running a standard filter housing, check that the filter hasn't been over tightened, this can cause the paper insert to twist , collapsing the pleats in the filter reducing flow!
Well I ordered a new oil filler cap so we can make an adapter for the mechanical oil pressure gauge. So that is my next step. Its a neat idea that I came across on here.
We don't drive in winter so if all else fails we will up the oil viscosity. When we changed the oil last, the filter was fine. Not crushed or anything, and no glitter or debris. Oil was good. Sent a sample off to Blackstone.
I'll update when when get the adapter made and tested the pressure.
Well I ordered a new oil filler cap so we can make an adapter for the mechanical oil pressure gauge. So that is my next step?
Don't understand this one, did you mean to make a adapter fitting for the oil pressure sensor to run mechanical gauge ?
I got the idea from here:
https://rennlist.com/forums/996-turb...-pressure.html
I like that it would be quick and easy to do this, rather than mess around with the oil sender unit. There a reason it would be bad? An extra cap is nothing to get.
You need to be connected to the main oil gallery for oil pressure, there is a removable plug on bank one head , this oil filler cap thing, I think you are confusing oil pressure with measuring the crankcase breather efficiency like if you had a bad AOS and was using a manometer, that's something completely different !
Just to reiterate - you
cannot
measure the engine oil pressure with the oil filler cap. The thread you quoted says that they put a fitting on the engine filter
canister
and measured the engine oil pressure there.
Huh??? Well, whatever.....one cannot measure engine oil pressure at the oil filler cap.
This is the quote from the other thread:
Alright, so- we ran through the basic mechanical stuff because it was ~quick. Then we gave up and decided to check the oil pressure. To do this, I ordered a spare oil filter cap/lid, and drilled and tapped a 1/8" NPT hole in the old one. Not a bad trick if anyone else out there needs to check their pressure without tearing everything apart. - That'll be saved in my bin of "special tools".
Interesting. Worth a discussion. I wonder if Peter got it to work then. Pressure is force exerted in all directions equally in a fluid in a closed system, so you'd think that pressure could be measured anywhere in the system? I'm just brainstorming here.
Lol, now I want to try it just to see if it works.
Hmm ... I can see that with a gas, as a gas can be compressed, but a liquid is not compressible regardless of movement? I am not trolling, just brainstorming, by the way.
Don't worry, I am measuring form the spot you all say. But I want to try this out just for giggles.
Yeah but pressure is just resistance to flow, so in a narrow oil galley pressure will be different than when it floods into lets say the oil pan or even in the large pick up tube
But resistance to flow is viscosity and not related. Pressure is force over surface area and does not change within a closed system. But if the fluid is separated into different closed systems, then pressure can be different in each system.
Gas or liquid, same thing. It�s the difference between static pressure and dynamic pressure.
Dynamic pressure is used to calculate forces when a fluid is moving.
Think of a garden hose that�s 10� long versus one that�s 100� long attached to the same valve. The 100� hose will flow slower than the 10� hose, even if both have the same 50 lbs or pressure coming from the valve because the overall resistance in the 100� hose will slow the water down. That resistance is force that counteracts pressure forces.
If the hose is long enough, there will be no water coming out the other end of the hose. If that�s hard to believe, try to image a hose that long and the weight of the water in that hose, and tell me if you think you can push it, pick it up, or even move it. The weight is one problem, but the friction is really the major component.
