Hard Braking = Drop Oil Pressure

I am new to 996 ownership. I search the forum and did not see anything that addressed this situation. I had an unexpected experience related to hard braking and zero oil pressure and am looking for advice. Last night I was in 3rd gear at about 4k RPMs. A person pulled in front of me and stopped. I did not have an alternative lane option and did a very hard stop and depressed the clutch at the same time. The engine dropped to idle ~ 500rpm. The oil pressure dropped to zero and the oil light indicator came on. Within a couple of seconds, it went back up to about 1.1 bar. Is this normal behavior for the M96 engine or suggestions on how not to see this in the future. Car Details: 99 C2 Coupe 90K miles Oil Pressure at cold start: 5 bars Oil Pressure at warm idle: 1.1 bars Oil Pressure at 4K rpms 3.5 to 4bars Engine is stock Oil is Mobil One (5w-30) Is this normal under hard braking with the engine going to a low RPM situation? Or am I joined to another object, by an inclined plane, wrapped helically around an axis? (screwed?) Thanks in advance.

the oil pressure sending unit is prone to failure. It's very scary to see the warning light come on suddenly and the gauge drop to zero but once it starts happening it will happen again, randomly. Sharp turn, sudden braking, etc. Cheap to replace.

It could be that the 500 RPM caused the oil pressure drop. If my engine ran that slowly, I�d possibly also get an oil pressure warning light. In the old days, a carburetted engine could stall with hard braking due to the gas level being too high (in the float chamber) and spilling over due to deceleration forces. On this car, I�d be checking for fuel pressure, a clogged fuel filter, a kinked or loose fuel line, etc. Also, you might want to run a 5w-40 or 5w-50, as 30 weight oil could be a tad light and have lower oil pressure, exacerbating the issue.

If you are really using 5w-30 (and not a typo) that will also contribute to low pressure.

The low oil pressure reading is most likely the result of the oil in the engines sump sloshing forward sufficiently to starve the oil pickup momentarily. Even though the M96 engine's sump pan is baffled, I've read several accounts of 996's experiencing oil starvation on the track due to long sweeping turns which would have a similar effect on the oil as hard braking. That's primary reason people install seep sump kits, to avoid oil starvation.

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Below is at 4K RPM - with an LN deep sump, baffle and XP9 oil... 2 Bar at 4K RPM, WOT. Do not assume that a deep sump will resolve the issue, it did not for me.

Thank you everyone for your comments. Over the holidays, my work plan to solve this is: Installing the spin-on oil filter mod Switching over to the DT40 oil I have added to the inspect and repair list Oil pressure sending unit Fuel filter/Line inspection We will report back on results by effort.

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At the risk of over simplfing why do you wear a seat belt?

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Depends on the situation: On the track - to maintain position in the seat for better control of the car. On the street - it is the law, to avoid points that should be saved for ignoring maximum speed limits Also - to keep the damn light on the dash from going off.

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Forget about the spin-on and DT40, will do nothing for you. I personally think this is inferior to M1 and original oil filter for many reasons. Braking hard is the worst case scenario for the oiling system since there is high G forces. The X51 have an extra oil scavenge pump to cater for hard braking specifically. What you could do: -Check the oil sender connections. They sometimes need to be pressed together with a plier to make better contact. -Is the oil topped up? It should be checked when the engine is warm and the car is parked on a level surface. Check the manual how to do it correctly. Keep it full. The reason why you would see such a sharp pressure dop could be the same problem as me: The sump is running dry beacuse oil is pooling inside the engine. The solution to this was replacing the oil scavenge pumps. Before you go down the route of ordering new pumps you can easily take off the passenger side pump and check if it's worn, then you know what to do.

If your car is a manual 99 model it could have a cable operated throttle which has an idle control valve , this as it's called controls idle , it's like a mini throttle body and opens at set times to let air in to raise rpm and control the idle , of the valve is sticking as they do when they get funked up the idle can be low , 500 rpm is too low it should be more like 800 , if your idle is low check out the ICV ok

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The spin-on filter and DT40 is a personal preference. I am going up to a heavier weight as the current 30W is too low. The oil is just below the max line on the dipstick and one bar down on the electronic monitor. I will inspect/repair the oil sender. The first step is to check the connectors and do some testing. If that does not solve the issue, we will replace the sensor. I have not researched ways to check for a worn-out scavenge pump. Do you have any quick suggestions?

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Yes, it is cable operated. We will add the ICV to the Inspect and repair list.

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Try cleaning it first. remove it from the throttle body and clean the carbon buildup then use a 9V battery to trigger it a few times while spraying brake cleaner into the port. This worked for me.

Are you guys all sure about oil starvation due to hard braking? I�m only asking because anyone tracking their cars would probably have seen this, right? The brakes on this car pull the highest G-forces during braking, compared to cornering and acceleration, and I don�t recall anyone reporting oil pressure drops from extreme braking. In the turns, sure. Remember, his RPMs were 500, surely the main cause of low oil pressure.

My two-cents. The oil pressure sender going bad or having loose wires is a well documented issue. There are threads on her about replacing it. Mine did that for a while. It would come back up almost right away, or I could turn the car off and back on, and the pressure reading would come right back to normal. I replaced the sender, made sure the wires were secure, and it's never done that again. As far as I've seen, oil pressure drop while braking hard would be a brand new, never before seen, issue. There are well documented issues of oil pressure drop while cornering at high g's on a track, and lots of discussion of potential solutions, commercial products, etc., but this would be the first ever mentioned of it happening while braking. And even then, it's typically low oil pressure, not an instant drop to 0, which then instantly returns to normal. And people brake on a track, alot, and hard. Seems like it would have come up. That's not to say that you shouldn't check other basic things to make sure your engine is alright and running well. Oil level, etc. And maybe make sure it idles correctly at about 750-800 rpm (otherwise you should search vacuum leaks, idle throttle control, or other topics for a new search/thread) But definitely check the oil pressure sender before going down a rabbit hole of speculation and expensive engine modifications.

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+1. I didn�t know about the loose wire condition, that�s good to know.

Check your oil cold...on a level surface. Not warm. Check it before your first trip of the day. 5W-40 is the suggested weight.

Sure. There are several threads. First seems to be the largest, but the other two have good advice on tools to get to it. https://rennlist.com/forums/996-foru...-pressure.html https://rennlist.com/forums/996-foru...sensor-ez.html https://rennlist.com/forums/996-foru...ement-diy.html

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Bad advice. If you check it cold you don't take into account the oil which is in circulation in the engine. The manual states the correct way of checking the oil level, it's done hot for a reason. 0w-40 is the recommended oil. The actual hot weight is recommended by Porsche to be between 30-50(this is also in the manual). The manual also state that the oil pressure should be 3.5bar at 5k rpm when warm, if you got more than that you could use thinner oil. If you have less you should go thicker. I've studied oil selection in detail, this is not something I made up just right now. Honestly, read the manual, it's better than anything you read on the internet.

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If my memory is correct the manual says to replace oil & filter every 2 years or 15,000 miles. I'll take Jake and Charles' "internet" recommendation of 6 months or 5,000 miles, whichever comes first. Just my $.02, everyone is entitled to their own opinion.

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Nick, I've read the manual, too....but the manual is no longer "up to date" and Porsche has changed their recommendations. If you check it warm it will usually read lower than cold and you risk overfilling....which, as you know if you do know so much, is bad for the motor. Lemme ask you something...how on earth does measuring it warm "take into account oil that is in circulation in the engine"? When the engine is hot...ie at a gas station stop....there is more oil out in the engine...so what is this secret mechanism that "accounts for this"? Bad advice, plain and simple, check it cold like the overwhelming majority of users (and engine builders).....and just like the CAR automatically does when you start it. And, as Optionman said, I'll take Jake's recommendation on this one, too...but you are free to argue that as you did with Baz in another thread.

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Dude, really Next you'll say that 15K mile oil changes are recommended because that's what's in the manual? Careful who's advice you take people!

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Ranks right up there with his sage advise on bearings.

Oil level check :::: consistency is key, and the only way you will ever get a consistent reading on an m96 is after it has sat for 8-12hrs... It's not about the Hot Vs Cold, it's about the "drip time"...

Ask yourself if you should follow the engine constructor/builders advice or the internet. That should not be too hard to answer I guess. If you check the oil according to the manual you check it close to it's running condition. You will gauge how much oil is actually in the sump while driving. If you let it sit until cold, the oil inside the engine(which the scavenge pumps are supposed to pump back) drains slowly back to the sump. Hot oil also have larger volume. Checking according to the manual will give you a consistent reading. 99.9% of it is still valid. For example how to check the oil level. Memory serves you partly correct. The 2y/15k miles is the MAX. It also says to change more frequent during hard use. And, what do you think is the viscosity of the oil when run that long? If you change too often your essentially running thicker oil than is recommended. The IMS shaft(bearing) drives three oil pumps, running thicker oil puts more force on it. Put shortly, if you change oil too frequently you will shorten the life of the IMS bearing. Sending oil to Blackstone seams popular on this site, have you ever seen a report from a 996 stating the oil was not fit for use? I've worked as an engineer at one of the worlds biggest bearing manufacturer, if that matters? What makes you think Jake knows this better than the mechanics and engineers at Porsche who constructed and built this engine? From everything I know about this engine, the manual should be followed otherwise you run into problems. Hands up anyone who have a rebuilt engine.....

"What makes you think Jake knows this better than the mechanics and engineers at Porsche who constructed and built this engine?" If those same mechanics/engineers truly knew everything, Jake & LN wouldn't have the water-cooled Porsche business they have, correct? I mean the Porsche internal team clearly designed a perfect IMSB and cylinders that never score, so i agree that we should never question anything they suggest regarding M96 engines.

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You might want to ask yourself how many % of owners think they know better than Porsche and ignores the advice/directions in the manual. I'm surprised there aren't more engine failures.

Let me ask you...when you do an oil and filter change....do you start up and run your car to check the level? Do you run it and let it heat up between stages of topping it up after the change? I doubt you do. You wait for the cold new oil to drip down into the sump...and after several steps of topping and waiting for the drip, you accept the level on your dipstick and move on. Checking cold (or after sufficient drip time) will give you the greater consistency, indicating the amount that is in the sump...which, at that point would be the most oil you would see in the sump....which is what the oil capacity and measurement is based upon. The oil capacity in the manual doesn't have an asterisk that note "*oil capacity in sump when driving so we can take account all the oil spread about the motor". Now you are telling us that if we change oil toooo often, we will damage our cars. Please stop. BTW...as an engineer (especially if you are in product design and development), if you haven't learned something new about your own products and your own preconceptions from data generated in the field by the customer and skilled technicians who use your product and think you are all knowing, then you are willfully ignorant. We are experts in the products we make at my place, but we still learn things about real world performance that we never considered before by listening to voice of the customer. If you discount the feedback of skilled users (ie, Jake and Baz) out of hand because it didn't come from Porsche, you are committing an error. Further, considering a static document of 20 yrs ago as the "final word" on everything is also a bit out of touch with real world product evolution. Dunno about your company, but we've changed specs on products we've been making for 30 years over time. Regardless, I'm done with this one....those of us who check cold and run 5w-40 will continue to do so.

I refill the same amount of oil as I drain. Pour the old oil in old canisters and just check how much come out. Then I go for a gentle drive to heat everything up and when arriving home I check the oil and top up until it's full. Then after every drive (this is my enthusiast car, not my daily) I check oil (and all the other fluids) when coming back home to the garage. Before next drive I only have to check that there are no leaks and I'm good to go.

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Well you started this thread so you can go off topic if you want to confuse the topic. You wear a seat belt to prevent injuring yourself in case you have to stop suddenly, and throw your self forward into the steering wheel or worse. The oil in the pan is doing the same thing unless it has baffles to minimize sloshing to the front of the pan.

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Agree with this. I�ve measured my car�s oil at various times and temps and it�s very consistent with respect to each scenario: Hot after sitting for 5 mins: 1/2-way mark Cold after sitting for 12 hours: 7/8 full Hot after restarting for 5 seconds: 1/8 bar from the bottom

Back to the original post, my 2000 996 suffered from this after engine was rebuilt by a reputable Indy. Hard brake (ABS not activated), clutch in, oil light comes on, engine dies. Water temp below 200. I’ve not had a chance to look at the oil pressure light when this happens. Now that it’s winter, I haven’t seen this, obviously. Running 10w40 in summer.

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Interesting. But if the engine dies, I would expect zero oil pressure.

Hopefully the hot vs cold and the manual vs experience wars are over and we can get back on topic. Oil is at 3/4 or higher both manually and digitally checked. It is checked weekly when cold. It is then checked when the engine is warm a couple of hours after being driven (ample drip time). Based on the feedback, I am working on two separate but interconnected issues. One is the low oil pressure and the other is the low idle speed. My next two steps are: 1. Move to a 40W oil 2. Check for loose connections at the oil pressure sending unit. 3. Inspect and clean the ICV to deal with the low idle speeds. If that does not solve the issues, the next steps are: 1. Replace the oil pressure sender unit 2. Replace the fuel filter, check fuel lines for flow challenges. We will report back on the outcome, for other readers in the future.

It's the oil pressure sender unit. I had a similar experience. Was approaching a toll booth and got cut off, hit brakes hard and needle dropped to zero, got the center dash warning message, etc. Luckily this happened after i had already experienced the same event under normal driving conditions and knew it was the sending unit on the way out. The first time it happened i had a "WTF!" moment, but everything immediately returned to normal and the engine never cut out. Happened 2 or 3 more times before i got the car in to replace the sending unit. Never had a repeat since.

Quick Status Update: Idle Issue: Solved I did the following: new fuel filter new air filter cleaned the idle control valve cleaned the throttle body cleaned the MAF Result: The car is idling at 650ish with no AC and moves up to 800 with AC on. It is like driving a new car. Throttle response is so much nicer and crisper. The resulting driver's grin to the work effort was well worth it. Oil Pressure: Still Pending I have done the following: Changed to 40W oil Replaced the oil pressure sender unit Replaced the oil pressure relief valve and spring So the oil pressure at idle is sitting at 0.8. At 4,000RPM, the pressure is at 3.5. I am still getting zero oil pressure under heavy braking while the engine is at idle (not in gear). My next step is to have the oil pressure measured by a manual gauge to validate the readings. Any other thoughts on possible reasons for low oil pressure?

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OMG... I wonder if Nick L is related to Krazy K ?

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As i do disagree with a lot of Nicks conclusions, he was able to bring his oil pressure up un his car by replacing the oil pumps. It may be worth investigating in the op's car if the gauge is verified as accurate.

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By the very nature of what a oil pump does, It should never wear out unless it has way over 100,000 miles.

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Assuming you mean a primary oil pump, one that is always submerged and likely never has any air in the chambers that wear out, I tend to agree. But an oil pump can go bad, at least on some engine designs. But the oil pumps in the discussion, are scavenging pumps. They draw in air all the time, so I�m more skeptical on those. Not to mention Nick did take measurements of those, clearly showing some wear.

Oil Pressure: Still Pending Original oil pressure readings: Oil Pressure at cold start: 5 bars Oil Pressure at warm idle: 1.1 bars Oil Pressure at 4K rpms 3.5 to 4bars I have done the following: Changed to 40W oil Replaced the oil pressure sender unit Replaced the oil pressure relief valve and spring New Oil pressure readings: Oil Pressure at cold start: 4 bars Oil Pressure at warm idle: 0.7 bars Oil Pressure at 4K rpms 3.5 bars Tested the oil pressure with a manual gauge and are seeing 1.5 at idle and 4 bars at 4K rpm. The oil pressure at the engine is good. So, is it reasonable to have two bad oil pressure sender units? Faulty gauge? Bad wire connectors(extra resistance?) thoughts?

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100% typical with our cars and nothing is wrong per porsche. This is why the guys that track put aftermarket guages and sensors in.

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+1.

I have had my oil light come on on steep hills.I found the oil pressure sender connector to be oxydized ,cleaned it and it's been four years and works well. It did generate a oil temp code in memory. Before replacing anything take a look at the connector first..

Finally solved the problem, but what a shock to find the root cause of the issue. When I drove the car, I was not happy with the oil pressure. The oil pressure would fluctuate oddly. So I pulled the oil plan. Sitting on the bottom of the oil pan was one swirl pot with a loose bolt. The other swirl pot was loose. The real culprit was the oil pick up was hanging by one bolt with an air gap. The other bolt was sitting on the bottom of the pan. The pick up could swing. So, I replaced all the bolts, o-rings, and tightened everything up. Since then, no problems. Oil pressure is behaving just the way it should. This falls under the weird Dread Previous Owner syndrome. I am glad I found it, as this was a grenade waiting to explode. Thank you everyone for your assistance and feedback.

Glad you found the issue and fixed it, but what I really want to know is how long has this problem been effecting the oil pressure ie, when were the oil pick-up and swirl pots last bolted up??? I suppose his car has been driven gingerly since the last work done in the sump.

Awesome! File this one in the category 'Sins of Previous Owners'! I've fixed more than a few on mine.

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Yes, it has been driven gingerly with constant monitoring of unpredictable oil pressure. It has been this way since I purchased the car. The car came from an estate where the owner passed away. My PO conversations are at a dead end. With the oil pressure issue resolved, My 996 grin has increased as I dive into corners and focus on entry and exits and not the oil pressure gauge. Damn, these are fun cars to drive.