Water in oil

[tmmorris]

When I returned from flying today, two club members were scratching their heads over a small amount of water visible on the dipstick of a C152, and a little 'mayonnaise' around the rim of the filler tube. They asked my advice and I must admit I was stumped. In a car, you'd suspect a leaking gasket, but of course there is no water cooling system in a 152...

It had apparently been flown in IMC the previous day; it is kept outside. I suggested either rain or condensation, but what is the most likely reason and is it cause for concern?

Tim

[gasax]

Probably condensation.

Cause for concern - well it suggests it does not fly enough and does not get hot enough! I've seen it in engines which sit and then get a short flight. That is enough to start to drive the moisture out but the cooler parts of the engine cause it to condense.

The real concern is that there must be a lot of dampness in the engine and with a Lycoming having the cam up above the oil, corrosion is a real concern.

[tmmorris]

Odd because without checking the tech log I'd imagine it had been pretty busy recently. It's our main trainer and it has just been the weekend, after all. I'll have a look next time I'm there anyway.

Tim

[phiggsbroadband]

Hi.. It could be a collection one or all of these reasons....

Short Flights causing the engine to not reach temperature.
Low engine revs.
Not leaning the engine for max temperatures.
Flight in cold / damp IMC conditions.
Circuit training, where almost half the circuit is at low revs.

Also I am not too sure about the chemistry involved, but running rich
may produce more H2O than running lean.
Could a blocked crankcase breather be the cause?

One training PA38 I flew, consistantly had moose for oil on the dipstick;
Our current C172 is only used for flights of over 1-2 hours and has very clear oil.

Pete

[peterh337]

It's not unusual to find a milky sludge around the dipstick, and also under the rocker covers when they are removed at the Annual.

It seems to be a function of the brand of oil to some degree e.g. Exxon Elite used to do it a lot whereas Aeroshell 15W50 does it much less.

It also happens a lot more if doing short flights e.g. well under an hour.

That said, I've been on Aeroshell for ~2-3 years and have just come back from this trip (http://www.peter2000.co.uk/aviation/samothraki/) which is over 20hrs' flying

EGKA-LDSB 6:15
LDSB-LGSM 4:15
LGSM-LGAL 1:40
LGAL-LDZA 4:15
LDZA-EGKA 6:35

and when we did the "50 hr" service we found that sludge under the dipstick "knob"... so it's a bit of a mystery.

[A and C]

This is quite normal for the C152, the water is a bi- product of combustion and despite the aircraft doing enough flying to get the oil hot in the damp atmosphere of the UK is something that always happens.

Next time you see the aircraft taxi in take a good look at the crankcase breather outlet ( firewall left at the bottom) and as the aircraft is shut down you will see a condiserable amount of vapor and then water draining form the breather.

This water is a real problem in terms of internal corrosion and the aircraft that you fly are all run on Aeroshell W15W50, this oil has a corrosion inhibited, the result of using this oil can be seen when. The rocker box covers are removed to adjust the valve clearance, the rocker box covers on Lycomings are usually corrosion traps, on your clubs aircraft the insides of the rocker boxes are free from corrosion. My hope is that this reflects the condition of the parts of the engine that can't be seen and oil analysis seems to back this up.

[peterh337]

I used to get heavy sludge in the rocker boxes when I was running on Exxon Elite, despite doing 150hrs/year then.

[A and C]

The Aeroshell multigrade & plus oils seem to produce less sludge than the other oils but I have yet to see a Lycoming flown in Europe that is sludge free.

[Pilot.Lyons]

Its probably condensation... No water cooling so no real worry

[tmmorris]

Thanks all. A and C - we did try to ring you but you must have been working for a change...

Tim

[A and C]

You should try to iMessage, that works in the air !

[Sensible Flyer]

It's just condensed water vapour from combustion. The end of the filler neck and underneath the dipstick probably don't get hot enough to evaporate any water in the water/oil emulsion that accumulates there, which is why a small "build-up" is seen.
If you changed the oil, then inspected after 1 hour you'd probably see a similar accumulation as you would after 50 hours.