Wobbly oil pressure?

[Robertb]

Slight issue with the oil pressure in my newly aquired 2002 C4S;

The oil pressure gauge is fine for the most part, but occasionally starts flickering up and down between 3-5 on the gauge, before settling back at what might be a realistic level, or settling at 5 before falling back lower again.

Is this a sign of an engine about to die, or something less sinister like a sender or a dodgy connection?

Thanks,

 

[Richard_Hamilton]

It could well be a faulty oil pressure switch - my brother had exactly the same on his C4. I think it is a common problem. I don't remember the exact cost, but I have a feeling it was about £25 for the switch, and 1/2 hour to fit.

 

[toals]

My 2002 C2 oil pressure guage did exactly the same as you describe when I bought the car 2years ago. Brought it back to Porsche and they ran the diagnostics which gave NFF. Still does it from time to time at steady speed on motorway. Would not worry.

 

[Guest]

mine flickers too, always between 4.5 and 5.0 bar, but never lower for some reason.

 

[Guest]

I have also had this problem. It became apparent following a service at an OPC. The service manager said that it sometimes happens after an oil change, and is not an uncommon problem. Fortunately I have a Porsche warranty on my recently aquired 2003 C4 and the OPC changed the oil pressure switch sender under the warranty. Like you I was terrified when I first noticed the problem.

 

[Ian W]

This flickering up and down seems to be normal at low rpm - hold the revs steady at say, 2000, and the gauge will wobble up and down by up to 1 bar. As has been said in previous posts this seems to be due to the design of the oil pressure sender. My 3.4 did this and continued to do so after the sender was replaced. My current 3.6 does exactly the same.

There is a similar symptom that is more serious. If you see big changes in oil pressure at higher rpm (when the pressure has maxed-out) then there is a potentially serious problem. The Carrera engine has 2 oil scavenge pumps, one in each cylinder head, driven by the cam chains (the pumps engage in slots at the end of one of the cams) designed to quickly return oil from the heads to the sump. I've seen one of these fail with the result that oil pools in the head as it is only being returned slowly, by gravity, to the sump. (Or not being returned at all if you are cornering and the g-forces are directed towards that cylinder head). The level in the sump then falls to the point where oil isn't picked up by the main pump any more. The pressure then suddenly drops for a second or 2 until some oil has gone back in. Left unresolved, this will eventually total your engine as it is running dry when the pressure drops. Bear in mind you could get similar symptoms from nothing more than your oil level being very low, so check this first.

So, wobbles at part pressure (low rpm) = normal. Large pressure variation at high rpm = worry!!

Ian W

 

[Robertb]

OK, I will keep it under obs- I did some experimentation on the way home last night, and it does it most at about 2.5k rpm (i.e. trolling along at 50-60) It seemed to be doing it a bit less yesterday.

The car has just been serviced so I will assume a prob would have been picked up.

Edit to say, just spoke to OPC Solihull who said this was quite normal, and nothing to worry about.

 

[baptistsan]

Mine was doing the same after it was serviced. How long would this last for?

 

[rob.kellock]

Mine does this too. Has also just been serviced.

 

[baptistsan]

Took mine out today and noticed that at idle the oil pressure is sitting at 2, any ideas?

 

[delboy]

Out of interest, is the scavenge pump expensive?. I have a similar problem diagnosed to the pump..Very slight oil leak too

 

[Richard_Hamilton]

The pumps which scavenge the oil from the cylinder heads back to the sump are £102.01+VAT each. The main oil pressure pump is £322.10+.

 

[delboy]

Richard

Thank you. Was after a "ball park" figure but that's superb