oil pressure sending unit

[Jeremy911T]

Just replaced the oil pressure sending unit as part of my engine in triangle of death repair on my 1971 911T.Genuine Porsche part 1-10 bar unit. Prior to replacement pressure would be near 0 at idle and max 60 PSI at high RPM. Now it is 20 PSI at idle and goes as high as 100 at high RPM. Nothing else changed or switched. Is this a calibration issue with the new unit? Should I be worried here.?The car performs exactly the same as prior to installation.

Thanks,

Jeremy

[proporsche]

very likely they sold you the wrong oil press s.unit..have a look at the bars..old and new

Ivan

[HarryD]

Check the base of the sender. It should have the range stamped there. Also check the Part number. 901-741-551-01 (may be superseded by -02).

[Jeremy911T]

Originally Posted by proporsche

very likely they sold you the wrong oil press s.unit..have a look at the bars..old and new

Ivan

Looks like the correct number except the last number has been superceded by 2 instead of 1. It is a German made VDO with a 1-10 bar range. These are the same specs as the one I replaced. I had to put a scope back there to see the numbers. It is back in the triangle of death and I have eliminated the leaks in that area. THe only question I have is should I feel confident that this is a calibration issue with the new sending unit or is there a cause for concern? Again, nothing else was changed and the car performs just as before. Your input would be appreciated. Thx

[Jeremy911T]

Originally Posted by HarryD

Check the base of the sender. It should have the range stamped there. Also check the Part number. 901-741-551-01 (may be superseded by -02).

Looks like the correct number except the last number has been superceded by 2 instead of 1. It is a German made VDO with a 1-10 bar range. These are the same specs as the one I replaced. I had to put a scope back there to see the numbers. It is back in the triangle of death and I have eliminated the leaks in that area. THe only question I have is should I feel confident that this is a calibration issue with the new sending unit or is there a cause for concern? Again, nothing else was changed and the car performs just as before. Your input would be appreciated. Thx

[Walt Fricke]

If you have a compressor and a pressure regulator (like one you might use on the end of the hose for a paint sprayer), you can easily construct with a bit of drilling and tapping a suitable chunk of aluminum an adapter to test both old and new sensors. Measure the electrical resistance at various pressures you adjust with the regulator know. Compare.

To be fancier, you could then hook this system up to your gauge with some wires after you pull it out of the dash.

The very low pressure with the old sensor at warm idle may be a characteristic of the T from that era. I once decided not to purchase one after a test drive. After a spirited drive I stopped and looked at the gauge. Yikes, no thanks. Subsequently I learned this was kind of normal, and it was pressure at higher RPMs which mattered. I have always supposed the reason Porsche switched from a 10 bar sensor/gauge to the 5 bar system was because the old systm was too freaky, and the 5 bar system doubled where the needle was against the numbered background (changed the resolution).

It is the stamp - either "10bar" or "5bar" which should show the difference in sensors, but it seems both of yours say 10.

So here is a thought: As pressure increases, the resistance in the sensor rises. Which is why, if you unplug the sensor from the gauge somewhere, the gauge pegs. An open is infinite resistance in this design. From this it follows that if something like corrosion in a connector increases the resistance, the gauge will read higher. How long has the female connector been back there doing its job?

PITA to test/check/clean/add a new connector, alas. But perhaps you could pull it off and put it back on a number of times, sort of like rotating those fuses in the fuse box?

Mislabled sensor would be another possibility.