Oil Change... oh oh.... measurement issue....
04-03-2017 | 06:31 PM
#18
Rennlist Member
Joined: Jun 2007
Posts: 461
Likes: 4
Variation in oil level
Simple for my 997.2 C2S---if oil temp is around 150, oil level is down from top by maybe 1/3 qt- or 1/3 of the big middle bar from the top bar. After it reaches 200 or more it reads at the top bar. (Top bar is not top of range - it is the bottom of the top segment.) Obvious fluid variation, probably expansion. 1/3 qt out of 8 is not so much. Could be another factor, but that is my guess. 40k miles on mine, 5-40 Mobil 1 just changed.
04-03-2017 | 07:26 PM
#19
Race Director
Joined: Sep 2006
Posts: 19,034
Likes: 255
From: Centerton, AR
So..... more data......
Summary: I am taking my car to dealer for the next oil change in 5K miles (I do it every 5K) to check the health of the sender unit (or whatever Porsche calls it... probably "Technik Oilick MachoMeterhchk" or something like that). I am not getting any deep codes as seen by my Durametric.
Yesterday I did another measure.... not fully hot .... bout 175F.... and now got a NEW measurement, flashing under fill. Great....
So I added just over 1 quart which I suspected I would have to do..... took it for another spin about 175F and this time got.... wait for it.... one bar OVER!!! crap.... Did another measure later after drinking beers at a bar...... cam home and got the same reading....
This AM, I figured I would try and suck out some juice via the fill tube (a blatant act of Hooverism)... don't know if this would work, but worth a try..... but took it for another spin beforehand and now measures EXACTLY full. Sheesh! So I am going to leave it alone.
Actually, I am not too worried about this and can accept the maybe fact that our measuring systems just are not that accurate... think about it..... it is measuring very small increments of fluid that are spread out over the large surface area of our oil pan..... QUESTION: for one bar of measurement, how much change must there be in oil height in the pan? Think about it... it has to be tiny.
Marc may be on to something about temperatures...... however I think it may be something similar that is actually causing my reading variances.......... settle time.
Settle time: With the 997.2, you need about 1 minute of idle at temps over about 100F (??) before measuring. I do a little trick with this time..... I coast down my curvy driveway and bump into my garage. I have this all perfectly timed... enter my driveway, push the door button.... coast...... get the speed just perfect... bump into the garage... just under the moving door..... then check the oil. I now have about 30 seconds on the meter...... SO..... maybe given the shaking of the car, I am not letting the oil settle out fully.
To Marc's point, my temperatures at measurement are all over the place from over 200 to maybe 130F.
What disappointments me is the ultra sensitivity of this stupid thing.... hell, we are just measuring oil level... does it have to be this complex? Cripes!
Overall I am not worried that I am putting in erroneous levels as I measure what comes out to what I put in. I do, however, put more oil in that stated capacity by about .9 quart more than stated. Further, our car's oiling system is designed to handle lateral forces over 1G (others correct me if wrong)... that is a ton of sloshing around therefore I can't believe say, a 1/2 quart over under normal driving will do anything bad to the car. Heck, back in circa 2000-2008 (?), dealers routinely overfilled these things (oh wait... engines were blowing up crazy back then).
So, I probably have nothing to worry about given I am so darn careful.... but I haven't been to the Proctologist ...er um ... dealer.... in five or so years.... so what the heck.... time for a nice bending over sans grease. Stay tuned in 5K miles or so.
Peace
Bruce in Philly
Summary: I am taking my car to dealer for the next oil change in 5K miles (I do it every 5K) to check the health of the sender unit (or whatever Porsche calls it... probably "Technik Oilick MachoMeterhchk" or something like that). I am not getting any deep codes as seen by my Durametric.
Yesterday I did another measure.... not fully hot .... bout 175F.... and now got a NEW measurement, flashing under fill. Great....
So I added just over 1 quart which I suspected I would have to do..... took it for another spin about 175F and this time got.... wait for it.... one bar OVER!!! crap.... Did another measure later after drinking beers at a bar...... cam home and got the same reading....
This AM, I figured I would try and suck out some juice via the fill tube (a blatant act of Hooverism)... don't know if this would work, but worth a try..... but took it for another spin beforehand and now measures EXACTLY full. Sheesh! So I am going to leave it alone.
Actually, I am not too worried about this and can accept the maybe fact that our measuring systems just are not that accurate... think about it..... it is measuring very small increments of fluid that are spread out over the large surface area of our oil pan..... QUESTION: for one bar of measurement, how much change must there be in oil height in the pan? Think about it... it has to be tiny.
Marc may be on to something about temperatures...... however I think it may be something similar that is actually causing my reading variances.......... settle time.
Settle time: With the 997.2, you need about 1 minute of idle at temps over about 100F (??) before measuring. I do a little trick with this time..... I coast down my curvy driveway and bump into my garage. I have this all perfectly timed... enter my driveway, push the door button.... coast...... get the speed just perfect... bump into the garage... just under the moving door..... then check the oil. I now have about 30 seconds on the meter...... SO..... maybe given the shaking of the car, I am not letting the oil settle out fully.
To Marc's point, my temperatures at measurement are all over the place from over 200 to maybe 130F.
What disappointments me is the ultra sensitivity of this stupid thing.... hell, we are just measuring oil level... does it have to be this complex? Cripes!
Overall I am not worried that I am putting in erroneous levels as I measure what comes out to what I put in. I do, however, put more oil in that stated capacity by about .9 quart more than stated. Further, our car's oiling system is designed to handle lateral forces over 1G (others correct me if wrong)... that is a ton of sloshing around therefore I can't believe say, a 1/2 quart over under normal driving will do anything bad to the car. Heck, back in circa 2000-2008 (?), dealers routinely overfilled these things (oh wait... engines were blowing up crazy back then).
So, I probably have nothing to worry about given I am so darn careful.... but I haven't been to the Proctologist ...er um ... dealer.... in five or so years.... so what the heck.... time for a nice bending over sans grease. Stay tuned in 5K miles or so.
Peace
Bruce in Philly
The amount of variation you are seeing with the oil level is not due to temperature but to a bad level sensor is my WAG.
You have to be careful in dealing with a bad oil level sensor that you don't over fill or under fill the engine.
As I have stated a number of times the time to check the oil level sensor is at oil change time. A standard drain procedure is followed so the amount of oil left in the engine is the same then a specific amount of oil is added which should then have the oil level sensor displaying the correct level.
Now with adding or subtracting oil as you chase a variable oil level reading you might not know just how much oil is in the engine. In 5K miles you would know even with less confidence how much oil was in the engine.
If -- worst case -- the oil level gets real low the only way you would know is if the low oil pressure warning light came on. The oil level sensor may not function well enough to give you an early warning of a too low an oil level condition.
You have another problem in that you do not know just how much oil the engine takes, that is you do not have access to the factory fill amount for your specific car/VIN.
Thus you can't just drain the oil in such a way to ensure the oil remaining in the engine is correct and then put back in the amount of oil the factory says is the right amount of oil to add to the engine after a proper oil drain interval.
This is the time then if the oil level reading is incorrect the function of the oil level sensor is seriously called into question. A tech might have some other way to "test" or check the sensor reading.
I can tell you based on how the sensor works -- at least the one I have cut apart -- a varying reading is a good sign the sensor is bad. (Another is -- to state the obvious -- is if there is no reading.)
The sensor is a loop of special (nickel/chrome alloy) wire, bare, un-insulated at least the part that is submerged in the oil. If this wire breaks there is no reading. If the loop becomes loose from where it is held securely at the bottom of its protective plastic enclosure the loop of wire then moves about. Since all of the loop of bare wire may not be immersed in oil the reading will be wrong. The reading depends upon the wire being submerged in oil as the amount of heating the wire experiences and how this affects the wire's resistance is how the oil level is determined.
When it comes to oil level I don't like to take chances. Based on what I know or believe I know I would have the car at the dealer to have the oil drained overnight then the right amount of oil added back into the engine. The tech then will confirm the oil level sensor reading agrees with the amount of oil in the engine. If it does then that's that.
Actually the tech might take a couple of short test drives then arrange to check the oil level again after each test drive to ensure the reading is correct time after time. If there is any variation this could arise if the sensor is acting up in which case then the sensor needs to be replaced (assuming the problem is traceable to some other part of the engine wiring system or the DME).