DaveK

I've mentioned a few times before that my oil pressure is fairly low at idle (just over 1 when warm). It didn't use to concern me - however, it does a little now.

Last year, my oil pressure light came on quite often when the engine was hot, as I pulled away and revs (and hence pressure) dropped. Although it has done it occasionally since I owned the car, it did it many times last year.

It's already started doing it this year - it did it a couple of times this week (when the car was at normal operating temp) and it did it a lot yesterday (stuck in stationary traffic on the M3).

Oil pressure is fine as the revs climb, but I don't feel comfortable with the warning light coming on all through the summer whenever the car is warm and stationary.

Any ideas?

Smokin

Dave,

A few ideas.. all or some of which may be lame... You are forwarned.

1. Could the oil pressure sending unit be bad? Might be worth swapping out.
2. Could you have a bad oil pump or at least a clogged screen somewhere?
3. Would it be possible for the thermostat to be stuck closed resulting in a low pressure? Are you sure your thermostat opens and closes? (Not sure if this would have anything to do with it... Just a thought.)
4. What weight oil are you running. Could it be too thin?

Like I said... Some or all may be dumb questions.

DaveK

Possible - although unlikely. I had it replaced a couple of years ago. It might be the cheapest first option though.

Maybe - but I guess that would mean rebuild time.

I'm pretty sure it opens - I checked it not that long ago (which suggests it was definitely opening last year) - but I will check the next time I use the car.

Think it's got Magnatec in it, although not 100% sure.

Jeremy Pinsly

Oil pressure sending unit could still be the problem, especially if the light goes on at idle. When you are running at higher RPMs with the pressure higher, the light probably stays off, and when you come to a stop, the light comes on?

Double check your oil level just to make sure you have enough there. If not, sending unit might be on the fritz.....

DaveK

It's not when I come to a stop - or at idle. Tends to be just after I pull away, when the revs dipped.

Jeremy Pinsly

Still could be the pressure sending unit. IIRC, my car had a similar problem but only when the revs dipped too.

springer3

Dave:

I have had two bad oil sending units in 911s. I found a worn oil pump during a rebuild, and wanted to replace it until I saw the price. The old pump is still doing fine.

I am running Mobile 1 10W-30 and don't get a low oil pressure light when the engine is running. I don't let the revs dip below idle when resuming from a stop. In any 911 previous to the 964 that would stall the engine. You had to get the revs up over 1000 before engaging the clutch. I still drive that way, even though I know the 3.6 has good low-end grunt.

If the car runs well, I would not even think about an engine rebuild. With a good synthetic, the engine has protection at low oil pressure. I don't believe thicker oil is the answer to low oil pressure at idle. Oil is also a coolant, and faster flow all the time is more important than higher pressure at idle.

Try a different oil, or change driving style just a little.

DaveK

Car runs fine. Service is next month, so will try a thicker oil and see how it behaves.

JET951

stay away from so called "synthetic oils" such as Mobil one,(which is category 3 oil) the minimum you should run in your 964(obviously depending on ambient temp) is a 20/50, but this is only my opinion in which case we have been working on porsches over 20 years. but hey what would i know.
sean

parsecnc4

Why would Mobil One be something to stay away from? Although it may not be the "best" in the world, should it still be better to conventional dino oil? And what is "category 3" oil as oppose to others?

I am curious to know if one should just stick with dino and change it out more often.

ppashley

Hey DaveK

I had similar issues with my 993 about a month ago, as did a chap from Sweden on the 964 Turbo board last week.

I feared the worst, but turned out to be a bad OP sensor.

Here is a video of the sender on my 993 showing these symptoms:
http://www.youtube.com/watch?v=HK4c9uJ8Dc8

I ended up changing the sensor out twice, but now its fine, and the issue was just the sensor, nothing more.

Decide for yourself, I don't want to suggest that its not a big problem, just that it might not be.

Search my posts on the 993 board, and you can see the whole story. Useful reading.

One point, if you do switch out the sensor, make sure you order the part from the dealer, and not from ebay/ aftermarket. I hear they're VDO factory seconds.

Also, I switched oil viscosities, as a first step, and it made bugger all difference...

Good luck - it's worth getting to the bottom of this in case you have got an issue...

Phil

'95 993 Coupe
(Stock)

warmfuzzies

Mobil 1 is on the Porsche recommended list of oils, staying away from synthetics is just a blind side, they offer better protection at start up, and for longer....they are designed to be more stable at a greater operating range......just using a dino oil because you may or may not have problems is like hiding your eyes as a child and pretending it'l all go away if you don't look.

Try the oil sensor, or if you can Dave, get a proper oil pressure gauge and plumb that in, so you can get a definitive reading.

kevin.

Reformed

Just Curious, what should the idle pressure be, Mine normally sits at around 2 bar when warm but if it gets really warm (Rarely the oil temp gets that high) it drops to around the 1 bar mark, Is that normal?

warmfuzzies

Reformed, that's pretty good. Mine is usually 1.5 bar-2bar when warm, and down to about 1.2 bar when red hot, i.e. thermostat open and stuck in traffic. temp gauge at 9:30-10...
There's been much debate in the past about stuck open oil squirter's, or worn bottom end causing low oil pressure, nothing conclusive though.

Kevin.

JET951

category 3 oil is 100% mineral oil, sure it has a few additives which have been "Hydrocracked" if you dont know alreasy its called marketing, and thats because porsche is now run by accountants not engineers.Mobil gives porsche FREE oil to fill up every car that leaves the printing factory(mass produced) and for this favour porsche approves Mobil oil. we have had way too much experience to see the effects of such oils in older cars, and it is naive to think just because the oil company has such a nice pretty advertisment that it is suited to your cars. these Synthetic(dino with a few additives) oils are suited to later model cars with smaller oil galleries and such the engine has been built to suit the oil. i will not go through our findings as i will be here all day and for no benifit of my own. i pass on advice in which we have seen the effects of using unsuitible oils in these cars, and for that matter cars from that era. we have worked close with track orientated 951s, 930s, 928s. not to mention two 962s, a twin turbo offshore V8 bridge to bridge racer(2500hp). the 962s will only use dino 50 oil. absolutly under no circumstance will so called "synthetic" touch these cars. the offshore boat went through 6 engines(all had extreme top end wear and thrust bearing wear) until the change to 25/60 valvoline racing mineral, so far it has outlasted 5 of those previous engines with out rebuild! so how did the "synthetic" work better? but hey as i said before this is only what we have seen for ourselves. its your decision, its your car.
sean(hiding my eyes hoping it will all go away) if only it was that easy