Mr.Alex

Last two-three drives out I've noticed the oil pressure needle dipping a bit lower than usual than usual. Upon cold start the pressure is about 3.5-4 bars, and as it warms up my pressure was usually somewhere like 1.5bar or a tick above 1bar. But recently as it gets around 8-9oclock temp, the pressure started ticking a notch below 1bar as idle hunts a bit. I have no oil pressure warning light however, and via dip stick my oil level is around 3/4. Oil is BP 20/50. The only time I had the oil warning light come on was around a year ago when I was hooning on a particularly warm night, but never again.

Should I be concerned? Is there any way to test the sender without having to remove it? I see its behind the intake stacks, and I've never removed those before.

HalV

I would be concerned. I'm surprised that your oil light is not coming on with that low of oil pressure reading. When I had a flaky Oil Pressure sender and the car was hunting for idle the gauge would bounce around erratically near 1.5 bar. Sometimes the gauge would bounce under 1 bar the oil light would come on.

tfitch03

when mine went out a few months ago it pegged to full pressure. i think it is something you need to look into pretty soon.

Rocket Rob

What is your alternator voltage at idle? A weak alternator can alter the gauge readings.

mcreston

just had mine replaced on my 91 c4 after the car just randomly started dip in to sub 1 bar at idle after about 10 minutes of driving one day. I'd get the oil pressure light on and then when i'd start driving the light would go off but would always come back down to low pressure at a stop light.

when i started searching online i freaked out as i was finding people saying that it's either the oil pressure sender or some kind of tragic engine issue that requires a rebuild. the next day i took it to brian at the stable in San Francisco and they swapped out the oil pressure sender and all was right with the world.

just my experience. it's an easy swap so i'd start there.

keep us posted

B

Goughary

Ok hold on. My oil pressure gauge has always read low like that at idle. And then pegs itself on the high end as soon as I am no longer idling. I thought and was told this is totally normal.

Can someone tell me exactly how this is supposed to function? Maybe Alex's problem isn't a problem, or maybe mine, which seems similar to his, is a problem?

Olcha911

In my experience which includes 2 different senders (one went bad) on the same car, and two different senders on another car (both cars were 92 and 93 964s), they all operate ever so slightly different (provided they are not defective). As long as the oil light does not come on at hot idle, and the gauge pins at 5 bar when at 4k or higher RPM, you are fine.

Mr.Alex

This I didn't know. I recently had battery replaced and on start up I have been getting some howl from the engine bay, which sounds like it may be the alternator bearing. With car running a good alternator reading should be around 13-15V?

The car runs 100% though, will hit 5bar when getting on it.



How long has your gauge been giving this reading at idle? From past threads It seems 1bar is already the lower tier normal reading.


Is the pressure sender responsible for the warning light coming on as well, or is that a separate circuit sensor?

HalV

If I'm reading the wiring diagrams correctly, either a low pressure or high oil temp will trigger the same warning light.

Mr.Alex

Went through some logs of the service records, looks like the sender was replaced in 2011 with an FAE Brand Sender ~32$. I've read in a one or two other threads that a good sender will shoot to the top with the ignition on, and then lower itself once you fire up the engine. Can anyone confirm this for me with your cars? Currently mine just moves a tiny bit above zero with the ignition on.

porsche mania

Mine behaves like yours does, I've earthed mine today to check the gauge isn't sticking as I can't get higher than 4.5 bar, earring it out will cause the gauge to read full pressure. I then put a manual pressure gauge on the car and when my car says 3.5 it actually measures 6! The lesson here is don't trust the gauge as they're crap. My sender was brand new as well, should have left the old one on. My advice is take your car to a garage. If you read your manual it says your car is fine

FlyinTomato

I remember my needle is pointing at 3 oclock when idling. full when driving. is the idling part normal?
Will check iginition on, engine off when I get home.

Mr.Alex

Car feels good so I'm not too worried, but just not content with the gauge reading lower than it used too. Which brand did you get, Genuine Porsche, VDO, or FAE?

Sounds good. Idle will vary from car to car, even among rebuilds.

crg53

Your oil temp seems a bit high, that would account for the lower pressure at idle. Have you checked your oil cooler and fan for proper operation. You may just have a dirty oil cooler, if it's never been cleaned, I would start there first.
THIS will give you an idea, what a dirty oil cooler look like.

porsche mania

I fitted a genuine one, not sure what I'll get next. I've been told that no two senders will behave exactly the same so my advice is get it to your local shop and have them put a manual gauge on it, it only takes 10 mins with a cool motor and will give you the piece of mind you are looking for. Had my car back for a couple of months and haven't dared drive it properly as my gauge wouldn't read above 4 after a full rebuild. Just got back from its first thorough thrashing and can't stop grinning!