996 "hot" oil pressure mystery

This will be a long post. Please hang in there. I really need some good 996 people to brainstorm this with me. I got this 2000 996 in December of 2017 with 74,000 miles on it. Well taken care of and tight. I immediately changed all the fluids as well as the engine mounts. I used Driven 5w-40 because the previous owner offered it, as he was just getting ready to change the oil himself. The following June (2018), when the weather got hot, I started to hear lifter ticking. Now this was not "scary" ticking. I have quite a bit of experience with the 997, 996, 986, 987, 981 cars. The ticking was normal sounding but was relentless and obvious once hot. It got worse after a healthy flogging on the back roads every time. Additionally the oil pressure would drop almost a bar if the throttle was opened under load, at operating temperature. Combined with the ticking, I felt action was needed. I sent an oil sample off to Backstone Labs, flushed the engine with Risoline (properly), cleaned the sump (nothing abnormal found), replaced the oil pickup tube, updated the oil pressure relief valve + spring and filled her with Mobil 0W-40. The sump was clean and the oil filter element was normal. Blackstone came back with a good report. However all the same symptoms and conditions remained. I immediately replaced the oil with Mobil 5w-50. The symptoms subsided to a comfortable level. This June (2019), I performed the annual service and changed back to Mobil 0W-40. By July the ticking and pressure issues had returned. I worked through the FSM suggestions and began to doubt the oil pressure gauge and sender. I performed the same oil pressure tests with a proper pressure gauge tool in place of the sending unit. The results: 80^ oil temp at idle = 85 psi 160^ oil temp at idle = 23 psi (20 minutes of idling. Not driven.) 177^ oil temp at 5,000 rpm = 42-48psi (Not driven) (After a flogging on the back roads) 180^ oil temp at idle = 15 psi 180^ oil temp at 5,000 rpm = 37 psi Obviously not good! So, if you've hung in there and read all the way through this, I have but one question: WHAT THE F*** WOULD YOU DO NEXT? Thanks in advance! -Kerry

The lowest your oil pressure gets down to is 1 bar, correct? If that�s the case, I think 1 bar is fine for idle. However, you are not getting enough oil pressure at high RPM. Either your oil pump is failing, or you are losing pressure somewhere else along the line. Your bearings and engine tolerances could be the problem. I guess I would start with replacing the oil pump to see if that resolves the issue.

Those pressures are not an issue, that's just how oil works. Hot oil is less viscous ('less thick') than cold oil, so hot oil will always result in a lower oil pressure than cold. You're experiencing oil-overheating. When you go for a 'flogging', which I will interpret as very spirited driving, you're heating the oil even further, making it even less viscous and hence yet again lower oil pressure. You're running the oil out-of-spec, so to say. It was designed for <212F nominal operation. There's a good reason that racing oils are of a lot higher viscosity (up to Xw-60 or above), so they keep their film strength at elevated temperatures. Beyond 212F, properties of normal engine oil start to deteriorate. What you actually need is better cooling for your application. So an extra radiator, and maybe a lower temp thermostat along with that so it takes longer for the oil to run hot. n.b. Oil temp is always higher than coolant temp, and the temperature gauge on your dash is not an accurate measure of coolant temp by any means. In the summer, on public roads where your average velocity will be well below 50mph, our cars' cooling is horribly inadequate if you abuse it. Constant hard acceleration / deceleration without any chance for it to cool itself at high speeds (like it would on a straight on a track), is about the worst thing you could do to a car. I wouldn't be surprised if this is a main offender in initiating bore scoring. If a lifter has gone bad, I don't see it repairing itself with simple oil changes. You'd have to replace the offending lifter.

Lifters generally don't "tick" in these engines... There are several other things that do, but not the lifters (although it's "possible" the probability is extremely low). The Oil thing is a whole other can of worms, which I'm not going to venture into! Good luck with the diagnosis

Are you running the canister type filter? Over time the spring for the bypass valve can get weak allowing too much oil to bypass. Either get a new canister/filter or upgrade to the LN Engineering spin-on adapter with a filter with no bypass. That's what I have and no oil pressure problems.

At full throttle, your oil pressure should be well over 60 PSI (5 bar). And stop using Mobil 0W40. And stop mixing Mobil with Driven. These two brands don't like the cross pollination. Stick with the Driven or the Mobil 5W50.

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The bypass in the canister won't drop oil pressure, since it doesn't bypass to the sump. It just bypasses the filter element, but stays within the high-pressure tract. Upgrading to LN spin-on won't help. The pre-filter bypass cylinder+spring assembly is the only bypass channel that would affect oil pressure. That spring/cylinder sometimes fails too, but then OP should be seeing issues at cold idle as well.

I guess "flogging" sounds like "abuse". Not what I meant. I mean spirited driving on roads between 4,000 and 6,500 rpm. Every modern Porsche in good shape should be able to handle this. I have track experience, both DE and competition, so I'm aware of the differences. The oil temps I took are a direct reading of the oil itself and not the coolant, engine block, etc. At 180^ the oil is not overheated. I'm open to the oil filter suggestion, but even when a filter goes into "bypass" the internal oil pressure should not change unless the oil filter has disintegrated and blocked passages. Am I incorrect in my line of thinking? I fear there might be some validity to oil pump failure or wear. However I've read multiple times that this engine is not known for pump wear. Believe me, I have been reading post after post on multiple sights for about a year before I decided to start this thread. As you guys have stated the idle pressure is not scary regardless of temperature. The hot, high rpm pressure is. One thought I've been toying with is oil aeration. Apparently (per my reading) there are two plastic units inside the sump that help to reduce oil foaming. I payed no attention to these when I had the sump open as it was my first time in there and I already had a game plan. Any of you guys think this could be a possibility? I mean aeration definitely causes lower pressures in fluids.

What is the actual oil temperature then? Just ^180 or do you have precise measurements? How are you measuring it? Your pressure does look on the low side at 5000rpm 177F, should be straight 5 bar, though the temperature dependency of this pressure beyond that temp seems simply normal. However, 85PSI cold idle should also not be possible afaik. The bypass valve to the sump should bleed excess pressure beyond 5 bar (72 PSI), so you might want to look into that one still.

those pressures are low, period. My car has low pressure, and at 240 degrees of oil temp, I still see over 40psi at 5k rpm. At 180 or thereabouts, you are not overheating the oil. You can try a 5w50 but you may simply be masking an issue. Also, keep in mind that flow and pressure are inversely correlated.

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You can easily tell if aeration is a problem by driving your car at a normal level and get your engine up to full temp by driving it for 20 mins. Not spirited driving. Then perform high RPM pressure test. If you have good pressure in this case, then aeration could be the problem. If aeration is the problem, it can take quite some time for the oil to settle but pressure drops after aeration usually result in pressure going back up after the engine settles down. It�s hard to tell because there is often a temperature difference, too. But as you said, you are measuring oil temp properly and not extrapolating or guessing. 180F oil temp is nowhere near hot and your oil viscosity at that temp, even with a �low� 40w oil should be pretty thick - enough for good oil pressure. I believe the manual calls for a minimum of 3.5 bar at 5,000 RPM. 3.5 bar is about 50psi. Most folks are showing 70 on the dash gauge at this speed.

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They are low indeed. I just don't trust his temp numbers. He states 180'ish F oil temp, which is 82 degrees C, after spirited driving. It is simply not possible with the standard thermostat, the coolant will already be way hotter than that, let alone the oil. Even with the low temp stat, which I have, I only see 80c in the winter while cruising on the highway, and that is coolant temperature. There's simply no way his oil is at 180F after 'spirited driving' in the summer. Either way, his oil pressure is low compared to mine as well, I agree.

OP, do you know if your engine has a DOF style IMSB installed? Some have external oil line from bank 1 can cover to the IMSB flange (external visual inspection) and some requir punching a small hole at the IMS oil pump end (will require removing the oil pump to inspect). I would also remove and chexk the scavenge pumps.

I would revisit your main oil pump by-pass again. The main by-pass is your oil flow control. It allows less oil flow when cold (by-passes more), and more oil flow when hot (by-passes less) . Your symptoms are directly opposite, too much flow/pressure cold (85psi) , not enough oil flow/pressure hot (37psi) . Make sure the bore is smooth, no scoring, and no debris in the oil pump housing.

Okay, we are getting somewhere! Maybe my temp probe IS faulty. It's a through the drain plug type with adapters for different cars. It's a tool that I've had for a while. Could be..... I was pondering the bypass valve on my drive home from work last night. I agree that the results are opposite. I am unaware of a DOF style IMSB. This is the first I've heard of it. I will check. That's a good idea to test for aeration. Will do! For the record, Mobil 5W-50 really didn't perform any miracles. Better, yes, but not a solid solution. So I have some things to do. It will take me a little time to complete these. I really appreciate all of you hanging with me on this. It's very helpful to bounce ideas around. Stay tuned, I'll report back!

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It rarely is. Truth is, the difference between 40w and 50w viscosity Numbers when hot is a much smaller number than the differences between them while cold. I only gained about 0.3-0.5 bar switching from 40w to 50w hot idle pressure, which sounds good in theory, but when pressure goes up, volume goes down and heat retention goes up. So there are trade offs.

Is this all happening at normal coolant temps ?? As they can be directly related to oil pressure, I'm sure that you could have some sort of engine cooling deficiency which could translate as low oil pressure when hot as the oil is getting thinner than normal ?? Also using heavier weight oil would improve this as the thicker oil at the same temp would improve pressure , tell me I'm wrong ??

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You are not wrong, but heavier oil won�t help enough to make enough of a difference. Correct, oil temps are often lower than water temps during warmup (the first 20 mins), but then they flip flop after that. The oil cooler in this engine is cooled by the water but is an oil heater during the warmup phase.

Same thing happened to me as well. I also have a 2000 996 and just had the engine re-built. I was using a 15w40 full synthetic oil and notice when coolant temps reached over 180 my oil pressure went down. I now use a synthetic blend of 20W50 which seems to help especially during the summer months. I also deploy my rear spoiler if I'm driving on the back roads for a long period of time to help cool the engine. If I keep the engine temps to around 180 to 200, my oil pressure is around 2.5 to 3 at 2500 rpms. I get very little to no tapping at all by doing this. I'm not an expert but this worked for me.

Okay, I'm back with more results. I hope you guys didn't wander too far away. The IMSB was replaced 10,000 miles ago with a LN unit. I replaced the oil bypass spring and plunger (again) with new OEM parts (again). I also replaced the oil filter and cut the old one open. Nothing was found. Not one single piece of plastic, rubber or metal. The oil that came from the bypass was caught in a clean beaker and left 24 hours to settle out anything. Still not a speck of material. The used bypass plunger and spring were a year old with only 2,200 miles on them. This plunger showed a small area of scrape or wear at the very top. The bore looked good but you obviously cannot see or feel all the way up in there. Even a bore camera doesn't really help. Because of the "spot", I chose to polish the new plunger gently with 600 grit soaked in oil. It's amazing how rough they are from the factory! I also discovered that I can read the oil temperature through Durametric. Christ on a bike! I should have known that to begin with. So now I have new data, but I'm still not out of the woods. Here goes: The oil is still Mobil1 0w-40 with 350 miles on it. The level is correct. Ambient temperature was in the lower 80's. Coolant - 87.4F Oil - 77.9F Pressure - 65 to 75 psi at idle (bouncing needle) Coolant - 195.4F Oil - 187.3F Pressure - 20 psi at idle (20 minutes later, needle steady) Drove the car for 45 minutes like Grandma. Never over 3,000rpm. Never over 65. Light on the throttle. Coolant - 211.6F Oil - 206.24F Pressure - 15psi at idle (needle steady) Engine at 5,000rpm, per FSM Coolant - 215.6F Oil - 217F Pressure - 30-35psi (needle bouncing a lot) Additionally the "tick" I mentioned earlier comes and goes. It is on the left bank and sounds exactly like a single lifter. Temperature and pressure has nothing to do with it's comings and goings. However this engine rattles really bad for about 10-15 seconds after sitting for 3-4 days. Maybe a clue...IDK.... Can you guys work with my data? Suggestions before I start pulling the engine apart? I love these cars but I don't enjoy pulling engines down anymore. Thanks in advance! -Kerry

Have you replaced your oil pressure sender? None of my needles have ever "bounced".

I'm referring to an oil gauge tool directly connected to the engine at the sender location.

Try to turn the key on but don't start the car. If the oil pressure gauge is not pointing at 0, then it suggest the oil pressure sender isn't right.

Using engine oil cleaners tends to deposit the gunk in the lifters which have the tiniest orifice in the engine. The only fix is to replace the lifter.

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Your cold oil pressure is better now than before, it was too high before indicating a sticking main by-pass. It is correct now, so maybe you are in the vicinity of your problem.I'm not sure if revisiting your by-pass valve and spring + bore has partially fixed some of your issue, or the data is not reliable enough. The hot idle pressure of 1 bar is ok. There is no real spec on the hot idle pressure, but we all know 1 bar is normal. 30-35 psi at 5k is very low, you should have a min of 60psi at 4k, this indicates low "flow". What brand oil filter are you using? Possibly a worn oil pump gears( easy to pop the cover off and inspect), another possibility is a stopped up oil cooler (although I have never seen one). If it's a 996.1 you could disconnect the vario-cam solinoilds to see if there is a loss of oil pressure when they are energized (like a blow out plug)..It might also be helpful if you graph pressure at every 1k rpm (ie 1k 2k 3k 4k 5k).. One more suggestion, pull the green rubber caps from the valve cover and inspect the ends of the cams, there is a plug in the end of the cams that I have seen come out !!!

So interesting. Question: How is the main oil pump driven - gear off the crank? Seems like the readings suggest the pump vanes are turning normally at idle but intermittently at high RPM.

Pump is driven by a keyed shaft coming out of the intermediate shaft.

If the sender has never been replaced, I�d replace that and see. Of you could tap the oil line and measure it that way. Idle pressure at 1bar is fine. It doesn�t make sense that you have 2 bar at 5000 RPM.

Mike: All of these measurements are being taken from a tap directly from the engine. I'm not using the dash gauge or factory sending unit. I'm using a very accurate oil pressure gauge tool. This is why I'm so concerned! Poschetech3: Good suggestions! I'll follow up as soon as I can spend some "quality time" with her. BTW, I read one article by a 996 owner who had similar problems, including lifter tick.The solution had to do with the "swirl pots" in the sump. One was clogged. Does this make sense to you guys?

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What does the bouncing needle look like? Can you post a video or describe it? Does the hot pressure voice between 30-35 or does it swing wildly up to 50/60 for a brief moment? I wonder what the time response of the needle is? For example, on my car, the gauge has maybe 1-1.5-second delay and is dampened. So let�s say my oil pickup sucks air on the racetrack for a couple seconds where pressure was 60psi, but the needle drops to 30psi for a couple of seconds. Real (effective) oil pressure was 5, 10, or 20 for a couple of seconds, but because it was previously at 60, the average of 30 is displayed. Have you pulled the sump plate yet? Could the oil pickup be sucking air? If the pump is good and not sucking air, and the bypass valves are not resonating back and forth (rapidly opening and closing), then something in the engine could be opening and closing an oil passage - maybe a failed bearing, tensioner, or another item...

Mike, the bouncing needle looks like a bypass valve vibrating off of it's seat or air bubbles passing through oil galleries. At cold start-up the bounce is mild and short-lived, maybe 15 to 30 seconds before stabilizing. When hot, at 5,000rpm, it sweeps wildly between 30 and 50ish before settling to a 30-35psi range. The gauge is not dampened. It's an instant reading type. The hose is only 20" long and it is a high quality tool. I trust it. I pulled the sump plate in June of 2018 because of the ticking lifter(s). I replaced the oil pickup tube, bypass plunger and spring. All OEM Porsche parts. There were a few tiny pieces (5 to 10 Grape-Nuts sized) of Nylon-type plastic in there. The chain guides had been replaced 10,000 miles earlier and I have seen this stuff in a couple of other Porsche engines so I was not concerned. I did not pull, check or inspect the "swirl pots" at all. Otherwise the sump was very, very clean. Re-read my starting post as to the results. I'm going to perform the suggestions that you and Porschetech3 have given first, then pull the sump plate and double check everything. The oil filters I have used so far are MAHLE, K&N and STP. No difference in results.... For what it's worth, when that lifter quits ticking you can hear nothing but injectors firing and exhaust. It runs very smooth and quiet. Drivability and power is seamless. Quite a conundrum indeed!

I'm curious to know if to much gasket sealer may have been used on the valve covers? Do you see any oozing on the edges?

Almost none. They good grey stuff where I can see it.

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I was told by the Porsche rep to use anaerobic (sp?) gasket sealer for the valve covers. I have a 996 with similar issues. Only difference is my oil pressure is dropping to 1.5 at idle after the engine warms up. My engine was serviced with cam pos sensors and vario pos sensors before it came to me. I was told that the scavenging oil pump in the cyl head could cause a disaster if not reinstalled how they were removed. How could I tell that they are in the right place?

Well, 3 weeks later, I have removed the sump plate and found no problems. The pickup tube and it's o-ring were fine. The mating flanges are flat and square. The "swirl pots" are clean. Ugh! Porschetech3: I forgot all about removing the cam plugs for inspection. I'll order 4 new ones and get right on that. A couple of questions: 1: Are those new cam plugs a PITA to get back in? Not much free space in there you know. 2: Are there any pitfalls when removing the oil pump plate? I only plan to remove the exhaust and mount crossmember to do so. I do not plan to drop the engine at this point. Is there more to do that I am not seeing?

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The cam caps/seals are easy to remove and reinstall, just poke a hole in the center with an ice-pick and lever them out, then to reinstall just push them in untill seated. You are exactly correct in removing the oil pump plate. No need to drop then engine..

Excellent my friend! Thanks!

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#1 - Be careful not to push too hard when reinstalling the cam plugs - you can push it into the cavity (ask how I know) - and it's not easy to get it back out...but it can be done without removing the cam cover (ask me how I know)... #2 - Rear Bumper? Might make things a little easier...

Well....The cam plugs are intact and the oil pump internals are damn near perfect. Hell, the pump gears, housing and face plate don't even have a distinctive wear pattern in them yet! I'm stumped and have gone as far as I can reasonably go. The only two things I can think of (and this is speculation) are leaking chain tensioners or excessive bearing clearances. This engine does have a single-mass lightweight flywheel on it. Maybe the crankshaft has hammered the main bearings from flexing. I don't know....I'm just frustrated and throwing darts at ideas now. I think that the oil analysis would have shown evidence of excessive bearing material or even journal wear. I've witnessed two leaking chain tensioners in my time but it is a rare thing. Neither were on well maintained engines and not on Porsches. Sadness has set in... Time to reassemble, fill with 5w-50 or 15w-50 and hope for the best. I appreciate everyone's input!

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Kerry, I can't tell you how many horror stories I've read when these cars are married up to lightweight flywheels. Most of the trustworthy experts here on the forums strongly recommend sticking with the OEM LuK dual mass flywheel. Aside from that, I would be more concerned about the ticking sound. Have you watched Jake Raby's Bore Scoring series on YouTube? That would be a good first start. Also, why not post some videos for us to evaluate?

If they used the right parts, the lightweight flywheel should be paired with a SPRING center disk, If they used the standard solid disk it can make stuff pretty noisy.. And very hard to identify the source. A tired injector can also make a loud ticking noise.. (Rarer but worth looking at. ) Tired tensioner pulley. Exhaust leak Cracked cat Alternator bearing Just tossing stuff out there..

Anything else ever come to light on this issue? I'm seeing very similar behavior and curious to know if you ever found a root cause?

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My car also has the same issues as the OP. I have 51k miles on mine. Once the lifter tick starts, If I hold 2,000rpm for about 20 seconds at a stop, the ticking goes away. With the hotter days here in Socal, the lifter tick is more common. I was really hoping to find some sort of resolution in this thread. I might just start throwing all my money at a cooling system upgrade.