View Full Version : B767 rise in oil level

4th Mar 2009, 12:13
My colleague recently handled a 767 a/c with a P&W4000 or a GE engine that had one of its engine oil indications rise by at least 4 units 1 hr after engine shutdown.It arrived with optimum eng oil level. They all thought it must be an indication problem(E&I). But when they opened the eng oil cap, oil just flowed out until it came to its normal level. Oil was normal, not foamy or bubbly. If its oil loss, there could be 101 reasons, but oil rise. The only reason i can think of is a problem with pressure relief valves. According to the capt, the indications were normal throughout the flight. Any other reasons u guys can think of ?

4th Mar 2009, 12:17
I don't know the 76 but on most planes if you have an oil level rise it is do to an internal leak in the fuel cooled oil cooler.



BAe146s make me cry
4th Mar 2009, 12:30

Agree with your comments, but this is 1 hour after engine shutdown.
There would be other bigger issues if the FOHE had a leak!


If oil samples & consistency/levels/consumption/Px is within limits and px/scavenge filters are clean, your operator may deem it satisfactory.

However, it could be indicative of a problem. Further investigation reqd me thinks. Anything in the FIM Chapter 79-00-00?


6th Mar 2009, 11:40
Thanks alot guys. Anyway, the FE decided the a/c could fly after the excess oil came out. All of us on ground were expecting a RTB or an ATB.

6th Mar 2009, 11:57
the 767 PW has still 8 units when indication is actually zero.
just for info.

6th Mar 2009, 12:49
Had the servicing guys topped up the oil for whatever reason whilst the donk was running?

6th Mar 2009, 13:06
As a general rule, with most jet/turbine engines, oil level check and servicing should be made within a certain "time" from shutdown. I understand we did it within 30 minutes for the JT9D-7Q on the 747. If performed a longer time after shutdown, the oil level will increase in its tank.
If you still wish to check/service the oil, motor the engine for 30 seconds, then check the level. If there is a problem with real "increase" of oil level, then it is a leak in the fuel-oil heat exchanger.
Happy contrails

Swedish Steve
6th Mar 2009, 14:23
Yes I find the B767 PW4000 goes up after shutdown. We have learned not to check the oil level straight away, but wait about 20 mins. The cockpit indication usually rises 2 or 3 qts in that time.

7th Mar 2009, 01:49
On our Pratt's....they will check the oil only between 45minutes and 4 hours after shutdown.

7th Mar 2009, 14:13
Yup, am aware of that "window" to check the eng oil of between 5 to 30 mins depending on the eng type although 4 hrs seems too long. We didn't top up anything on our side. Gives me another possible suspect :E. So say u top up soon after the eng shut down to full tank, would the tank be theoretically be more than full after a few hrs when all the oil begins to flow back to the oil tank. Thanks once again for all your ideas:ok:

9th Mar 2009, 18:29
Going back to the original post all P&Ws the oil level is bound to rise during the period of 30 min to 1 hour after shutdown, its the way PW4000 engines oil system is designed, and its not just on B767's, Pratts fitted on all the aircraft behave the same whether its on B777, B747, A330 or your B767s...:E

23rd Mar 2009, 20:40

If I am not mistaken on Boeing 737-200 (JT8D) left engine oil tank holds more oil than the right engine (4 gallons for the left and 3.5 gallons for the right).
I am wondering if other aircraft have such thing.

Thank you.

24th Mar 2009, 09:35
If I am not mistaken on Boeing 737-200 (JT8D) left engine oil tank holds more oil than the right engine (4 gallons for the left and 3.5 gallons for the right).
I am wondering if other aircraft have such thing.

I believe it is something to do with the tilt of the engine on the pylons rather than the eng oil tank capacity itself.

24th Mar 2009, 10:19
You would certainly smell the fuel in the oil when you open the cap if the FCOC had an internal leak. This may be a case of overfilling. On occasions if you dry motor the engine then fill the tank you could overfill the motor(normally reads 2 to 3 litres down). This is because the pressure pump puts it in, but the scavenge pumps are not turning fast enought to take it out of the bearing sumps and back to the tank.

24th Mar 2009, 13:30
How about a physical collapse somewhere within the system, reducing the volume capacity. A drain and refill (to check how much oil goes in against how much is indicated) would check that??

24th Mar 2009, 16:39
Some engines have an anti-syphon device that prevent the oil in the supply line back peddling back into the oil-tank after shutdown, never worked pratts only CFM.

Sounds like over-servicing, it can be very easy to do if the oil servicing has not been actioned within the shutdown window!

Lot of experience with this on the 757s causing all sorts of mischief! :cool:

24th Mar 2009, 17:32

I guess for some engines the oil get siphoned from bearing sumps to oil tank especially after certain period of time after engine shutdown. The AMM chapter 12 can give more information regarding engine oil servicing.

My question was not related to the rise of oil level. The oil tank have the same capacity for both engine (same tank). Left engine tank holds more oil than the right engine tank because of the dihedral wing and the interchangeability of engine (position 1 & 2, or left & right).

Back to my question: I am wondering if other aircraft (new & old, Boeing, Airbus,...) have such things ? Please let me know.


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