Is My Oil Temperature Too Hot

[wnsgc]

Greetings,

I'm in the process of getting my 911 ready for the new season (yippee...). Anyway, today I was driving for around 30 minutes and the outside temperature was around 50 degrees. As I was returning to my house, I noticed the oil temperature was a bit high. Here is a picture of the gauge:




I checked the oil sending and return lines to the thermostat (in the rear passenger wheel well) and both tubes were very warm (not quite hot), the tubes between the thermostat and the front external oil cooler were cold. As a matter of fact, the engine itself wasn't that hot, not like it can get during the summer after driving for an hour or so. All this being said, here are my questions:

1) Can the oil temperature sensor/sending unit go bad? If so, I assume it can give a faulty reading back to the gauge?
2) If the thermostat is closed, does the oil recycle back into the oil tank, in othe words, does the oil flow thru the closed thermostat and just return or is the oil stopped/blocked in the tube?
3) Is this temperature reading "normal"? And I use the word normal lightly?

Thanks.

[FenderGuy]

Looks normal to me, unless you get the temp conversion its going to play tricks on your mind, my sc was like that and then I switched over and i was happier to know the true temps

[MT930]

Looks like it's with in normal limits to me. Maybe on the cooler side.

[qcwang]

I think your temps are normal.

Even though I have an SC, I think our gauges are the same?
If you take a flashlight and look to the far left of the gauge face, you should see numbers corresponding to the lines.
On my gauge:
bottom white block=60 deg C=140 F
middle line=90 C=194F
upper line=120 C=248F
upper red block=150 C=302F

As I understand operating temps are about 212 F (someone correct me if I am incorrect as your model might be different), so your gauge if the same as mine, the needle is showing below 194 F.

My operating temps in So Cal ranges from a low where your needle is, to a high at about the same position but just above the white line your needle is currenlty below.

The highest it has ever been was tad above the upper white line after a 20 min track session. I have since upgraded to a Carrera oil cooler that you probably already have.

Hope this helps.
Stay Cool!

[spuggy]

not my picture, but snagged it here a long time ago...



Most guys would consider the oil nicely up to operating temperature where you describe it, and just suitable to start exceeding 4000 RPM or developing boost...

I start to keep an eye on the gauge when the oil gets to 210-220. That only happens for me in heavy traffic with no airflow over the FMOC, or high (100+) ambients.

[DRACO A5OG]

That is the full operating temperature. BTW if look at your OEM guage from the side you will actually see the numbers. I always wondered why the Porsche engineers opted to hide the numbers.

You should keep the RPM's under 3K until it reaches the middle of the cold range.

[wnsgc]

Thanks for the feedback and re-assurance on my temperature. But regarding my two other questions, can the oil temperature sensor go bad, thus causing faulty gauge readings or is that something that almost never happens. And regarding the thermostat, when its closed (thus not allowing oil to flow to the front-external oil cooler), does oil get to the thermostat and the go back in the return line or is the oil in the send and return lines stationary and not moving? Sorry if this is a dumb question, but I have no idea what happens to the oil when the thermostat is closed.

Thanks again.

[Flieger]

When the thermostat is closed, no oil circulates through the lines to a front oil cooler. The oil bypasses the front circuit and makes a smaller loop. The oil goes from engine to filter to tank to engine.

I have no experience with this part, but I would agree that a temperature sender could go bad just like any other part can. I have not heard of this happening like I have with oil pressure and oil level sensors.

[RoninLB]

shouldn't readings be same relative to needle position?

[spuggy]

Originally Posted by RoninLB

shouldn't readings be same relative to needle position?

They would be, if the sender units were calibrated the same, but they're not...

The gauge itself merely reads full-scale deflection on 12V ("fails pegged").

The senders for the numbered gauges are different, you need to swap that over as well if you backdate a later car to the numbered gauge or you'll get incorrect readings.

Add; That said, my '77 gauge looks almost like it would match the needle deflection for whatever year that "unmarked" gauge was from (excuse cellphone pic):



Numbered gauges just rock. The old 140 PSI oil pressure gauge lets you know what the internal engine thermostat is doing on cold startup too (hint: with a 930 oil pump, you're running 100 PSI @ 2,000 RPM until that sucker opens)...

[Miguel Antonett]

Perfect!!!!!!!!!!!!!!

[RoninLB]

last year of #'s was '77


my engine operates routinely between a needle width below and above 170.

2 needle widths above for 110F deserts at 80-90.

it doesn't run cooler because of carbs.