Carrera 996 oil Pressure

[e7lew]

I have a 1999 Porsche Carrera the oil pressure when the car is very hot drop in less than 1 Is it normal?

Note: I live in a very hot country

[e7lew]

Edited February 18, 2012 by Loren
Original image linked to (offensive) remote site - removed link and re-added image

[logray]

That is definately abnormal, especially if it's 21.5C outside and the engine coolant temp does not appear to be abnormally high.

What weight and brand oil are you running? Is the oil level sufficient?

It could be a broken oil pressure relief spring, as this has been documented here and elsewhere before.

[e7lew]

I Use Mobil 1, oil filter new

oil gauge is ok

oil pressure rise more when the engine temperature down to 80 or a little more

and less than 1 when the engine temperature increased as shown in the picture above

What should I do now Do I have to worry about this

I asked some Mechanical Engineers here and they said that it's normal, especially at high engine temperature and oil

[logray]

edit: it could also be the oil pressure sender, but how does the oil pressure behave when not at idle? For example what does it read on cold startup, and what does it read at 3000 rpm in 5th gear.

It is abnormal, especially if you are using a 0w40 weight oil, and especially with the engine operating temp indicating what it is on your picture, and especially if it's only 70F outside..

But the oil weight certainly does have a bearing on this, do you know what grade of oil you are using? Was it filled at a dealer? Is the oil level (amount of oil in the engine) proper?

Try some searching for oil pressure relief spring. When they break, the pressure can drop like that as you've observed. It's a very simple fix, basically a $10 spring and one bolt to remove under the engine to replace it. You can also replace the oil pressure piston at the same time, it is aslo very inexpensive. It's worth replacing to try and remedy that problem, because the other "fixes" for low oil pressure are not so easy or inexpensive.

Edited February 16, 2012 by logray

[pcvinsel]

...

Try some searching for oil pressure relief spring.

...

I did a search for exactly what you said, "oil pressure relief spring" and the only 2 post found are in this thread that says to do a search. I know it's off-topic but am I the only one who find the search facilities in this forum pretty close to useless?

Any links to related threads on this topic would be greatly appreciated since my oil pressure sensor went belly up & I need to replace it. I'd like to also replace anything else that makes sense while I'm in there...

Peter

[logray]

google "rennlist 996 oil pressure relief spring"

[e7lew]

it reads on cold startup around 4.8 4.9

it read at 3000 rpm in 5th gear 2.9

i use 0w40 ( my fisrt time )

oil level is ok

When at idle long time pressure drop under 1.0

[logray]

All normal except idle pressure.

I would start with the oil pressure relief spring and piston.

[e7lew]

does this mean oil pump is ok ?

[fbgh2o]

Has the oil pressure warning light ever come on?

This sounds a lot like my car at idle. When hot it will idle around 1.1 to 1.3 bars (with the AC off - turning on the AC will add about 150 to 200 rpm on the enginer and that's good for 0.2 bar of pressure). I have seen 1 bar and maybe just a bit under when the exteror temperature is 85F + and I have been pushing the car.

You say at "long idle" it drops below 1 bar. How long? The 1999 996 do not have the best cooling system around and prolonged idling when hot will likely heat the oil significantly resulting in lower pressure.

The pressure at 3000 rpm seems a bit low. Running 5w40 I am always at 3.8 to 4.2 bar when on the highway and always over 3 bar in city driving where the engine runs hotter.

In addition to Logray's suggestion, I would also check the function of the oil pressure sender. It may also be starting to fail reslting in readings that are slightly off. It's a relatively low cost part and easy to replace.

[logray]

Yes I did recomend the oil pressure sender as well above, but unless someone can explain why it only goes bad when the engine is idling and hot, I'm not sure that is where I would look first. It might be worth cleaning the sender contacts at least.

I think the manual states 3 bar at 5000 rpm engine fully warm is considered normal.

His cold start and crusing numbers sound normal.

I doubt his oil temp is much higher than the coolant temp, and it shouldn't be enough to warrant running less than 0.5 bar at idle, his pic looks like around 0.35 bar. It might be worth reading out the oil temperature from the DME at the same time the pressure reads this low.

If the oil pump was bad or if there was a blockage in the oil pickup tube.you prob wouldn't see 5 bar at cold start and 3 bar at 3000 rpm. There might be other symptoms too if those were the case.

I still advocate going after the simple things first before tackling the more difficult, example first try relief spring. Even just pull the spring out and inspect it. Literally once the oil is drained it is one bolt and about 30 seconds of time to inspect, dead simple to access right under the car.

Then I would go for cleaning the sender contacts and oil pressure sender.

Then if still not good, pull the sump check for picckup tube blockage, pull the oil pump cover inspect for wear in gears and surfaces.

There's always an oddball chance it's woring or a fault in the gauge, you could also hookup an external oil pressure gauge to the top of the 1-3 camshaft cover oil pressure test port.

[e7lew]

I did not see oil pressure warning ligh never so far

Yesterday, I left the car about 30 minutes temperature was 92c , 0.7 bar not less

tested while idling it reads at 5000 rpm 3.9 bar

Thanks for the tips i'll let you know soon

[e7lew]

i changed oil pressure sender and oil pressure relief spring with piston nothing changed

any advice ?

[logray]

When the pressure reads 0.7 bar (closer to normal) or 0.35-0.40 bar (as pictured in your second post), did you read what the oil temeperature was using an obd2 diagnostics computer? I'm not talking about what the temperature gauge says on the dash, because that gauge is not accurate. What does the ECU (DME) say it is reading from the oil temperature sensor? Other temperatures I would want to read out from the computer at the same time:

Oil temperature

ECTS (engine coolant temp)

IATS (intake temp)

Engine compartment temp

Outdoor air temp

Although Porsche did recommend 0w40 at one time, they now generally recommend 5w40 worldwide (although 0w40 and 5w50 are still approved). Mobil 1 5w50 would be an approved oil to use.

However, in warmer climates many people will run a higher viscosity oil, for example Mobil 1 15w50, even though it is not on the approved list. I have read of Porsche dealerships in warmer parts of the USA who dispense this oil during fill ups. Of course, you could also request 5w50 oil, which is an approved oil. I have tried this oil myself and observed higher oil pressures.

It might be worth an oil grade change to see if this resolves the pressure problem, however I would still take this in steps and want to see what the engine operating parameters are first (see above temperature sensors to monitor).

Still though, unless it is really very very hot, 0w40 should provide pressure higher than the 0.35 to 0.40 bar in your second post, which is indicative of a problem that oil grade change might not resolve (or is just covering up).

Edited February 18, 2012 by logray

[e7lew]

Was a long day with specialists

Everyone agreed that the oil pump good and proves this through the oil gauge when driving the car

I was at The official agent for Porsche told me under 1 normal

When the vehicle model 99 is normal to have a slight weakness

Oil pressure gauge now 7 to 6 bar not less When the temperature is about 90c

i Will try 5w50

am sure that the problem is not from oil pump there is another problem somewhere

[ledson]

Have you figured this out? I'm going through the exact same thing.

Thanks!

[e7lew]

Have you figured this out? I'm going through the exact same thing.

Thanks!

i changed oil pump

[ledson]

i changed oil pump

The whole oil pump? I changed the cover, but not the gears. I had some scoring on the cover.

[e7lew]

The specialist told me he changed the whole i trust him

I installed Used one in good condition not new

Edited June 23, 2012 by e7lew

[cayenne444]

I have the same problem but mine is 997 C4S 06 88k KM ,

@ Idel .75 when fully worm at hot day ,

After you change the oil pump what is the reading now?

Thanks,

Edited August 12, 2012 by cayenne444

[e7lew]

The car was sold before i solve the problem

[patrick hebert]

someone resolved issue?

I have same issue. 

cold 4,5 bar

and slowly, when going warm, on idle uniquely, little bit less than 1 bar on idle.

 

no noise or anything special 

oli level good 

 

so pretty same you describe.

it was the sender unit, oil pump, worst??

 

 

 

 

[JFP in PA]

Welcome to RennTech 

 

Porsche released an updated oil pump pressure regulating spring and pressure to address this for about $20, plus you can always check the accuracy of the dash display by temporarily connecting a known mechanical gauge; the dash display is not known for its accuracy.

[patrick hebert]

thank you a lot