Oil Tank Sender and Dipstick "update"?

[kugelfischer]

Hi All.
I recently bought a replacement oil tank sender for my '73 (911-641-541-02). I've been told that this "new" model sender needs to be used with the updated dipstick (930-107-731-00).
The new dipstick is slightly longer than my original and as such to get the oil level to register in the correct range I needed to put in less oil than I did with the old stick.
Any idea why the new sender and stick combo requires less oil to read correctly? Is there any chance that I'm under-filling the oil now?


Thanks!

[Jerome74911S]

Good question, but I'm sorry I can't answer it. My '74 may have a bad sender, therefore, I'm interested.

[DRACO A5OG]

If you have not done so, compare the old OSLU with the new one. I bet the path of the float is different lengths ergo the different dip stick.

[kugelfischer]

The "new" sender and dipstick are designed to work together. My question was more of "why are they different from before" ? With the new design you end up putting less oil in the car than before. Is there a reason or any downside to doing so?

[Joe Bob]

When checking the oil when warm, idling and on level ground.....who gives a daman about a 1/4 inch. You have a case of oil in the freaking system.....

[DRACO A5OG]

Originally Posted by kugelfischer

The "new" sender and dipstick are designed to work together. My question was more of "why are they different from before" ? With the new design you end up putting less oil in the car than before. Is there a reason or any downside to doing so?

That is strange, like any other superceded parts, sometime PAG just does not make sense.

BTW, you may need to calibrate the gauge, just remove and gently tweek up or down.

I am having an issue with the superceded AC temp control switch

[T77911S]

Originally Posted by Joe Bob

When checking the oil when warm, idling and on level ground.....who gives a daman about a 1/4 inch. You have a case of oil in the freaking system.....

finally!

[Grady Clay]

Well, here is some trivia:
First, the ’73 oil tank is Model Year 1973-only.
Obviously it was a big change from the ’72-only tank but also all earlier tanks.
The tank did not change for the ’73.5 introduction of CIS on the late 911T.

In 1974, the ‘impact bumper’ shock absorbers would interfere with the ’73 tank so the tanks were modified for clearance beginning with the 1974 model year.
When the supply of spare-part ’73 tanks were exhausted, there was supersession to the ’74 and later tanks.
I suspect some research will find a P+A notice suggesting (or requiring) a new sending unit and dipstick when installing the ’74 tank in a ’73 chassis.
My perception was the ’74 tank was lower to the ground (possibly larger) but that may only be my perception due to the bumper change.
If so, this may account for the change in sender and dipstick.

One other possible reason for lowering the recommended level in the tank was CIS was far more ‘sensitive’ to overfilling with oil.
The lower level gave more ‘clearance’.
(Remember, it was Porsche (P+A) that has to deal with the new owners not reading the manual.)
The ‘sensitivity’ is not the ease of overfilling but the consequences.
When you overfill MFI or carbs, the excess oil simply makes a mess running out of the air filter assembly ON the engine, usually remedied with a trip to the 25¢ car wash.
With CIS, the problem became one IN the engine.


My oil level recommendation is:
Keep the level to ‘as high as you can get away with’.
The highest level is just after sustained high-speed freeway use in very hot weather and then pulling off to a stop at idle.
The hotter it is and lower the idle; the higher the oil level.
That level should be less than what will cause an overflow into the intake system.

The reason for ‘high’ level is when cold, high rpm and extreme braking and cornering, the system can ‘cavitate’ (pick up air with the oil from the tank).
This is not good for engine bearings but they seem to tolerate the abuse.

SO … I set my level to the top limit when very hot and just after pulling off the freeway.

Best,
Grady

PS: If you have the ’73 tank and the ’74 tank in your hands, measure the capacity and the positions of the dipstick and sender.
Photos may help also.
Note the indentation for the bumper shock.
G.

[kugelfischer]

Thanks Grady! Sound advice as always.
"Keep the level to ‘as high as you can get away with’.".
Seems like the best course of action. As you mentioned, I was worried about cavitation under extreme driving conditions.
I was pretty sure the engineers didn't set the fill level arbitrarily and want to keep my engine alive for another 37+ years.

K