SecaBlue

I have surfed a few forums here and there and think that my oil pressure sender is on its way out. I have a '90 944S2 done 256000km, and after 5yrs of ownership over 7000km never had an issue with the oil pressure gauge, until yesterday.

Get in and drive with cold start. As soon as the engine fires, my oil gauge jumps straight to 5. After driving for approx 30mins at hwy speeds, it settled down to 4, and when I came to park letting the rpm down to idle, the gauge went straight down to just over 2. Blip the throttle, and it jumps up to 4 and back to 2, quite settled. I know the oil pressure is good, and has fresh oil from Porsche Centre in May this year.

4yrs ago I went over all the grounds on the car, removing, sanding, and reinstalling. The car ran better, lights better, etc etc. I also removed the instrument cluster, cleaning all the football contacts on the rear, new lightbulbs (non LED). Upon reinstall all the gauges worked perfectly. Battery is near new, and alternator is sending more than 14 volts.

I have read that I can try swapping the sender wires around - how easy is this to access? I don't have a workshop, but can potentially access a lift. Otherwise I know a new sender here in EU is approx 70 Euro, and the fitting is not so complex.

What are your thoughts?

931guru

You are describing normal operation on a 30 year old 944.

What you read is wrong. Swapping the wires will not fix anything.

walfreyydo

As 931guru mentioned, the description you gave is normal and matches almost exactly how my S2 behaves and also matches what is on Clarks: http://www.clarks-garage.com/shop-manual/lube-03.htm

SecaBlue

OK. Just that since I cleaned the footballs, the gauge was always just above 2 at idle, 3ish at lower rpm to 'cruise' rpm (100km/h), and 4 to 5 at higher rpm. Now it never sits on 3, and takes a long time to drop from 5 to 4 at highway rpm. Sometimes sitting between 4 and 5 until I let it idle. Maybe I am just being too pedantic?

931guru

Well, you could replace the oil pressure sender with a new one... come on, spend the money... what have you got to lose?

walfreyydo

When cold my oil gauge is almost always between 4-5 bar even at idle. Once the car fully warms up, its at 4-5 only at higher RPMs (over 3k) and at idle sits at around 2.5. If you think about it, as engine speed increases, so does the oil pump and thus pressure increases with RPM.

What you describe is normal and I think you may be over thinking things, but it wont hurt to change out the sending unit - fairly easy to access and about $100 if I remember correctly

SecaBlue

Cool... thanks for the input, as I can rest a little easier now. Will leave it then until next year and see how it behaves.

Zirconocene

I always that that what you are describing is the normal way things are. I rationalize it as the oil "thinning" a bit as it get up to temperature, leading to lower pumping pressures at idle. Like others, I saw exactly what you are describing this morning in my 928, on the way in to work. I think I would be pretty freaked out if it was any other way.

Good luck