Oil level sensor question

[Michael T]

My oil level is at the top mark on the dipstick at 180 degrees on a level surface. When I start the car on a level surface after sitting all night the gauge registers at about one third (towards the bottom). As the oil warms to 180 degrees the gauges pegs to the top. Is this a sign the sending unit is going bad?

[db_cooper]

Sounds like your oil level gauge is fine. I think your oil level is too high.

I would suggest running the oil level on the dipstick at the 1/2 point between the MIN and MAX marks when the engine is hot.

Most 911s like to blow off the first quart when you run the oil level at the MAX mark, it is not needed. It just pumps the oil/oil vapor into the intake manifold.

And at 180*f..the engine is just getting warm..at 210*f you are overfilled with oil.

Much less smoke on start-ups and you will be amazed at how your oil consumption will drop dramatically when you add oil to keep the oil level at the mid point on the dipstick.

Don't add any oil till the level on the dipstick is at the MIN mark, engine hot. Then add about 1/2 quart and drive. The oil level on the dipstick should get to about 1/2.

Your oil gauge will probably show nothing when cold and about 1/2 hot when you do this.

[DRACO A5OG]

1st, what does the dip stick read at those temps/over night?

Remember the gauge is just a guide but dip stick is what you should depend on.

If they match then you have simply over filled it and OLSU is working as designed by PAG.

If not, then the OLSU will need servicing or replacement. Here is my tutorial on the service/replacement. Oil Level Sending Unit: How to Service / Repair / Maintain

Jim

[99hdtop]

You have too much oil in the car. At 180 degrees you should be in the center of the full and add marks. The oil level will rise more if your car reaches 220 degrees and will cause oil to be sucked into the airbox, then you will have a mess to clean up. Sounds like your sending unit is fine.

[Michael T]

I should have said I was getting a full dipstick measurement at 180+. A month ago my gauge would show just below the top mark at the same oil level. The gauge has also shown some erratic jumping at idle. Draco, do you have the link to your video mentioned in the link?

[JJ 911SC]

Originally Posted by Michael T

I should have said I was getting a full dipstick measurement at 180+...

If by full dipstick you mean at the Max mark, you got too much oil.

There is 1.75 Litres between Min and Max, so I would removed .75 Litre and check the dipstick again at 180

[db_cooper]

Interesting note on the oil level sensor..in 2008 I ordered a new one from our host, part number 911 641 541 02 M100. OEM Porsche part with the gasket. $67. I still have the receipt.

My old level sensor was very wobbly and not accurate.

I saw the excellent write up from Draco about rebuilding the oil level sensor and thought why would you do that? They are not that expensive, are they?

Same part number OEM Porsche sensor now is $158!

[DRACO A5OG]

Just click the pic, it will link you to the video on photobucket.

Yeah, $158, I'm a cheap basturd, that's why :-)

[Michael T]

Well I drained abot .75 litres of oil to get to the mid-point on the dipstick when hot. The gauge moves from the low end of the guage at startup to slowly pegging the guage at full temp. Probably the sensor.

I cleaned the area around the sender and the wire contacts, and still the same symptoms. I need to shrink wrap the center lead. I ordered a sender and gasket and will follow-up.


Before:

After:

[Porsche 2]

Back to your original comment and question, oil expands when it gets hotter, hence the difference in oil level between cold and hot.

[Michael T]

Decided to take off the ground screw and the copper male tab. This was the issue. I used 600 grit emory and sanded down the corrosion and oil buildup on the contact and the bottom of the nut. All is working well now. Also shrink wrapped the other contact.

[ClickClickBoom]

Originally Posted by Porsche 2

Back to your original comment and question, oil expands when it gets hotter, hence the difference in oil level between cold and hot.

Not even close but thanks for trying.


The Handbook of Industrial Oil Engineering: A Reference Book of Data ... - John Rome Battle - Google Books

Or

http://nvlpubs.nist.gov/nistpubs/jres/5/jresv5n5p985_A2b.pdf

[db_cooper]

Originally Posted by ClickClickBoom

Not even close but thanks for trying.


The Handbook of Industrial Oil Engineering: A Reference Book of Data ... - John Rome Battle - Google Books

Or

http://nvlpubs.nist.gov/nistpubs/jres/5/jresv5n5p985_A2b.pdf

I don't think the author(s) owned air cooled 911s..the oil level on the dipstick definitely goes up when the engine is hot..if my engine is at the MIN mark at 160*F and the engine oil gets to 210*F/220*F..the dipstick will read near the middle between the MIN and MAX marks.

[ClickClickBoom]

Originally Posted by db_cooper

I don't think the author(s) owned air cooled 911s..the oil level on the dipstick definitely goes up when the engine is hot..if my engine is at the MIN mark at 160*F and the engine oil gets to 210*F/220*F..the dipstick will read near the middle between the MIN and MAX marks.

Dry sump engine, takes awhile to scavenge completely after startup. As the oil heats the viscosity thins and then the oil returns to the sump faster and is then sent back to the tank, hence the illusion of expansion.

[Michael T]

I had no confusion about the oil level on the dipstick rising as the oil heated. It was that the dipstick level and the oil gauge level had a difference. The gauge was reading higher than the actual on the dipstick. When the oil level on the dipstick is at the midpoint, the gauge is now at the midpoint.

[DRACO A5OG]

Congrats, a much easier and cheaper fix

In your "before" pic, was that oil on the exterior? If so, you may want to consider replacing the gasket or just maintain it from fouling up your ground.

Lesson Fellas, Clean Your Grounds.

[db_cooper]

Originally Posted by ClickClickBoom

Dry sump engine, takes awhile to scavenge completely after startup. As the oil heats the viscosity thins and then the oil returns to the sump faster and is then sent back to the tank, hence the illusion of expansion.

The scavenge side of the oil pump (right side of the oil pump in the picture below) has about 100% more liter per minute flow than the main engine oil pump (left side of the pump in the picture below) side of the oil pump. It clears excess oil from the crankcase in a few seconds of running..specs (as I recall on the 3.2) are something like 60 liters per minute on the main engine oil pump at 6000 RPM..120 liters per minute at 6000 RPM on the scavenge side... The crankcase is emptied of oil very quickly once running.