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996 Low Oil Pressure problem (not sending unit)


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Hi all

 

I have a low oil pressure problem on my 2003 996 C4S RHD / ROW, Tiptronic.  Owned since 2012, oil change at least annually first with Mobil 0W40, more recently Fuchs or Liqui Moly (green) 5W/40.  Looking for help from anyone who has seen something similar - I've looked at various threads on this topic but couldn't find the exact symptoms.  

 

Last oil change was done in Sept 2018 with the Liqui Moly green.  About two months later, the "oil pressure too low" red light started to come on intermittently.  Either on start-up, or sometimes when slowing down or waiting at the lights.  It doesn't stay on forever, just flashes and goes.  Had the oil pressure sending unit replaced (its been faulty for a while and yes I know I should've replaced that way earlier.. now not sure if this has been masking the problem at hand)..  After replacing the unit, I assume the gauge is accurate and it shows:

 

- On cold start-up: gauge stays at zero for first 5-7 sec.  The red low oil pressure light flashes on, then the needle moves up to 3 bar max

- On warming up, the needle will drop and eventually settle on 0.8 bar (i.e. after 10 mins and water temp rises to normal operating temp)

- Oil pressure does NOT rise on acceleration - i.e. when rev to 3-4K, the needle doesn't move at all.  It used to move with the revs

 

I've also had the oil pressure relief spring / piston / gasket changed (and oil topped back up of course) with no difference.  I'm thinking of the following next steps (in order of complexity and $$):

 

1. oil change / filter change, check filter for metal and ensure it isn't collapsed / crushed

2. mechanical gauge to confirm that oil pressure is indeed low, and it isn't an electrical misreading

3. inspect oil sump - check for blockages in the oil pickup tube

4. drop engine - check oil pump for failure

5. rebuild engine - have reached out to a few builders who have said it could be crankshaft bearings worn, engine no longer to hold pressure.  I guess this would be worst case.

 

I hope it ain't 4 or 5, but something has worried me about this problem..  Why I say above this oil pressure problem might have been masked by the faulty sending unit?  My gauge used to rise to 1.5 bar even before the engine fired up but with ignition on.  My indy looked at that and laughed "how could there be oil pressure when the engine isn't on!"...  So when the engine did start the gauge showed 4.5 on cold start, and it would drop to about 2.x when at operating temp.  So..  if my sending unit was faulty and was adding an additional1.5 bar of pressure to the gauge..

 

Anyone experience similar?  Thanks.

 

Henry

 

 

 

 

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1 hour ago, henryhkl said:

Hi all

 

I have a low oil pressure problem on my 2003 996 C4S RHD / ROW, Tiptronic.  Owned since 2012, oil change at least annually first with Mobil 0W40, more recently Fuchs or Liqui Moly (green) 5W/40.  Looking for help from anyone who has seen something similar - I've looked at various threads on this topic but couldn't find the exact symptoms.  

 

Last oil change was done in Sept 2018 with the Liqui Moly green.  About two months later, the "oil pressure too low" red light started to come on intermittently.  Either on start-up, or sometimes when slowing down or waiting at the lights.  It doesn't stay on forever, just flashes and goes.  Had the oil pressure sending unit replaced (its been faulty for a while and yes I know I should've replaced that way earlier.. now not sure if this has been masking the problem at hand)..  After replacing the unit, I assume the gauge is accurate and it shows:

 

- On cold start-up: gauge stays at zero for first 5-7 sec.  The red low oil pressure light flashes on, then the needle moves up to 3 bar max

- On warming up, the needle will drop and eventually settle on 0.8 bar (i.e. after 10 mins and water temp rises to normal operating temp)

- Oil pressure does NOT rise on acceleration - i.e. when rev to 3-4K, the needle doesn't move at all.  It used to move with the revs

 

I've also had the oil pressure relief spring / piston / gasket changed (and oil topped back up of course) with no difference.  I'm thinking of the following next steps (in order of complexity and $$):

 

1. oil change / filter change, check filter for metal and ensure it isn't collapsed / crushed

2. mechanical gauge to confirm that oil pressure is indeed low, and it isn't an electrical misreading

3. inspect oil sump - check for blockages in the oil pickup tube

4. drop engine - check oil pump for failure

5. rebuild engine - have reached out to a few builders who have said it could be crankshaft bearings worn, engine no longer to hold pressure.  I guess this would be worst case.

 

I hope it ain't 4 or 5, but something has worried me about this problem..  Why I say above this oil pressure problem might have been masked by the faulty sending unit?  My gauge used to rise to 1.5 bar even before the engine fired up but with ignition on.  My indy looked at that and laughed "how could there be oil pressure when the engine isn't on!"...  So when the engine did start the gauge showed 4.5 on cold start, and it would drop to about 2.x when at operating temp.  So..  if my sending unit was faulty and was adding an additional1.5 bar of pressure to the gauge..

 

Anyone experience similar?  Thanks.

 

Henry

 

 

 

 

 

Welcome to RennTech:welcomeani:

 

THere is an inexpensive factory’s update (pressure relief piston, spring, and plug seal) that sells for about $20 US that addresses this exact issue.

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Thanks for the welcome and comments!

 

Oil Pressure Relief Valve - unfortunately I've had this replaced already.  It didn't make any difference.  This was the most recent thing I had done to the car.  I put in the new spring, plug seal and the updated 997. piston.  My indy said my old spring was slightly shorter than the new one, but otherwise it wasn't damaged.  I was really hoping this would solve it but it didn't.  

 

I'm not really losing coolant.  I can smell a little whiff of coolant when I put my nose near the rear wheel / engine bay area after a drive.  But it hasn't led to the level dropping significantly.  I had the radiators, expansion tank and cap replaced about three years ago.  In any case, the coolant smell has been there for years.  My AOS and water pump was replaced 3-4 years ago.

 

Agree that I should get my oil sump pan dropped first - see if anything is going on in there.  Hope I don't find some foil blocking the pickup mesh i.e. from the last oil change!

 

Regards

Henry

 

P.S. attaching a pic of the old OPRV and piston that was swapped out.  

  

IMG_20190203_162741.jpg

Edited by henryhkl
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Your approach seems like a good one.  I would do this:

Drain oil and remove oil sump pan.  Check oil pickup tube for debris.  Change oil filter, inspect, and replace with new oil filter and get a new canister (bypass valve in the canister may be stuck open or malfunctioning).  Reinstall oil sump pan then refill with new oil.  Remove oil sender unit and hook up a mechanical gauge to the fitting.  Check oil pressure at startup.  If it is good, might be a good idea to swap out the oil pressure sender unit again.  They have been known to be bad right out of the box.

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Thanks DBJoe. Good that you point out the potential problem with the sending units. Another thing that I can hope the problem to be!

 

I was wondering also if the two sending unit wires were reversed, what would happen? I understand the smaller terminal should be connected to the low pressure warning light, and the big terminal to the gauge. Just thinking......

 

One other thing, I read somewhere about the oil pump hex key drive wearing out on some 996s, although rare. This introduces play on the pump gears I think, and could cause the pump to fail. Well let's hope my problem doesn't get that far. 

 

BTW does anyone know if the Bentley's 996 manual cover this topic or have any additional troubleshooting tips? I'm considering to buy this book - having read the reviews on this forum. 

 

Thanks

Henry

 

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I don't think the sending unit wires can be swapped because they are of different sizes. I don't recall the Bentley manual has any troubleshooting steps about this problem. Even if it does, I don't think it will be more than what you can get out from this forum.

 

Once you inspect your oil filter and oil pick-up (both very simple to do), you will have a lot more info to decide on the next steps. I would add sending the oil for UOA to make sure it's not contaminated by oil and also verify metal wear. If indeed the internal bearing tolerance is getting so bad that it doesn't hold oil pressure, accelerated metal wear should also show up.

 

 

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  • 2 weeks later...

I have this problem too the difference is That I know I don't have low oil pressure (pressure was check with a manometer) right after installing the engine, old one blow up, the low pressure light will come on when hot with the old engine and before I had the chance to put the new oil sender unit the engine blow up, now with the new sender unit on the new engine I'm still having the same problem.

Should I buy a 2nd oil sender sensor? or could  my cluster instrument just be bad?

Edited by JDRZ
add words.
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Well!  I dodged a bullet.  

 

I couldn't bear watching my ride sitting sick like that in the carpark.  I didn't want to wait any longer for my indy , as I was getting the feeling he was losing interest in further  troubleshooting my problem.  So on Monday I had it towed back to the dealer.  Porsche HK charged $200 (USD) for diagnosis, i.e. to find out the cause of the red "engine oil pressure too low" warning light.  I didn't want to risk driving it further.  

 

1st fix - oil pressure sensor / sending unit.  Dealer test drove the car and couldn't hear any tapping or knocking noise.  Hence they suggested to replace this first.  I didn't disagree, considering DBJoe's advice that the sending units could be bad out of the box.  $250 parts and labour.  Unfortunately this didn't fix it and by that time the dealer was already draining my oil.  Apparently the oil filter was "twisted" and had collapsed..  They said it wasn't an OEM filter.   Refilled with Porsche oil-on-tap, they started her up and oil pressure all back to normal!  5 bar on cold start, dropping to 2.5 warmed.  Needle rising with revs.   Oil / filter change - $600.  

 

Dealer said my oil was a bit sludgey and asked whether its been many years since I last changed.  Hell no! I replied.  I change oil at least once a year.  The last two changes were done at Oct 2018, and Nov 2017.  I was quite surprised to hear this.  The oil is only 3 months old, how could it be sludgey?  

 

All up including the towing fee, my wallet is $1,200 lighter..  Could I have done it cheaper?  Probably.  But considering I was fearing the worst, i.e. full engine rebuild, this wasn't the worst of outcomes.  I had not seriously thought it could be as simple as a twisted filter.  The dealer said they didn't know what could have caused it.  Was it install error?  Not sure, but I wouldn't have thought you could get an oil change wrong, right..

 

Anyway, all good now!  My engine appears to be holding good pressure.  I'm still a bit concerned about their "sludgey" comment and hence I might change the oil in six months instead of a year, just to see if all is still well.  

 

Interestingly, the dealer used "Porsche Classic" 10w60 Mobil1 for the fill..  They said given the 996 is now a classic car, it should be getting 10w60.  Not wanting to start an oil thread here, but is anyone else out there using 10w60 in their 996s?

 

 

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25 minutes ago, henryhkl said:

Well!  I dodged a bullet.  

 

I couldn't bear watching my ride sitting sick like that in the carpark.  I didn't want to wait any longer for my indy , as I was getting the feeling he was losing interest in further  troubleshooting my problem.  So on Monday I had it towed back to the dealer.  Porsche HK charged $200 (USD) for diagnosis, i.e. to find out the cause of the red "engine oil pressure too low" warning light.  I didn't want to risk driving it further.  

 

1st fix - oil pressure sensor / sending unit.  Dealer test drove the car and couldn't hear any tapping or knocking noise.  Hence they suggested to replace this first.  I didn't disagree, considering DBJoe's advice that the sending units could be bad out of the box.  $250 parts and labour.  Unfortunately this didn't fix it and by that time the dealer was already draining my oil.  Apparently the oil filter was "twisted" and had collapsed..  They said it wasn't an OEM filter.   Refilled with Porsche oil-on-tap, they started her up and oil pressure all back to normal!  5 bar on cold start, dropping to 2.5 warmed.  Needle rising with revs.   Oil / filter change - $600.  

 

Dealer said my oil was a bit sludgey and asked whether its been many years since I last changed.  Hell no! I replied.  I change oil at least once a year.  The last two changes were done at Oct 2018, and Nov 2017.  I was quite surprised to hear this.  The oil is only 3 months old, how could it be sludgey?  

 

All up including the towing fee, my wallet is $1,200 lighter..  Could I have done it cheaper?  Probably.  But considering I was fearing the worst, i.e. full engine rebuild, this wasn't the worst of outcomes.  I had not seriously thought it could be as simple as a twisted filter.  The dealer said they didn't know what could have caused it.  Was it install error?  Not sure, but I wouldn't have thought you could get an oil change wrong, right..

 

Anyway, all good now!  My engine appears to be holding good pressure.  I'm still a bit concerned about their "sludgey" comment and hence I might change the oil in six months instead of a year, just to see if all is still well.  

 

Interestingly, the dealer used "Porsche Classic" 10w60 Mobil1 for the fill..  They said given the 996 is now a classic car, it should be getting 10w60.  Not wanting to start an oil thread here, but is anyone else out there using 10w60 in their 996s?

 

 

 

The condition of the oil could be the result of the oil itself, who's oil did you have in it?

10W-60 is way too heavy for the water cooled engines, you should be using a quality full synthetic 5W-40 with high ZDDP levels.

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Agree with John about using 5w-40 oil. To get peace of mind, it would be good to send the oil for used oil analysis once you have 3~4k miles on the oil.

The UOA will tell you if you have any coolant in the oil (which could create the sludge you mentioned).

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Thanks all.  Car appears to be running fine right now.  Think I will keep driving it gently and monitor how things go, then change back out to some 5W 40 after 2k KMs.  I will do a UOA - just hope that blackstone will send their kits overseas.  

 

 

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