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Oil Pressure Drop on Take-off - SOLVED!

  • John_in_Aus
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3 weeks 5 days ago - 1 week 3 hours ago #22681 by John_in_Aus
Oil Pressure Drop on Take-off - SOLVED! was created by John_in_Aus
Hi Guys,

So I have a 2008 912 ULS with only 300 hours on the clock, and I have an issue that has me scratching my head.

My oil pressure ( and temp for that matter) is always low, and on take off, it's scary low.

So when I take off, it drops to below 30Psi - Maybe 20 or so. Then once I roll the throttle off a little it climbs back up to sit at just over 30, where it sits the entire flight. Even in idle on the ground it sits there.

The oil temp never gets over 75 in the cruise (yellow) and will only ever get to the green on a decent climb under power.

Any ideas? I have read everything from bad ground wire, to a dodgy sender - but same have changed the sender and the oil gauge itself, and it's still the same.

See pics - One is on take off ( the low one) and the other is the cruise.

Thanks in advance.
John

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Last edit: 1 week 3 hours ago by John_in_Aus.

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3 weeks 5 days ago #22685 by Bill Hertzel
Replied by Bill Hertzel on topic Oil Pressure Drop on Take-off - SOLVED!
Is this a new or chronic issue?
What was the typical pressure and temp for the first 300 hours?

It is time to determine if the readings are correct or the values are actually low.
Remove the Oil Pressure Sender and replace it with a basic mechanical gauge with a needle dial.
Start the engine and monitor the gauge from a short distance away.
CAUTION! Do Not stick your head in the spinning propeller! :ohmy:

Once the engine has heated up all that it usually does, stop the engine and remove the cap from the oil tank.
Pull the Dip Stick and insert a Kitchen thermometer in the Oil.
The Oil tank is before the Oil Cooler so it should read slightly higher than the panel gauge.

If the external gauge and thermometer match the panel instruments, the numbers are real.
Otherwise, it is a measurement problem.

Bill Hertzel
Rotax 912is
North Ridgeville, OH, USA
whertzel1@yahoo.com
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3 weeks 5 days ago #22686 by John_in_Aus
Replied by John_in_Aus on topic Oil Pressure Drop on Take-off - SOLVED!
Now that is an awesome idea! :)

Thank you! Talk about not seeing the forrest for the trees.

The pressures and temps have always been low, but I have never noticed the drop on take off before. Because I myself am only 100 hours in, during take off, I was not looking at instruments other than RPM, AS, and ALT (They are right in front of me) until I rolled off the the throttle a little after the initial climb, and then scanned the right hand side of the panel. The Pressure had somewhat rebounded since then - So I am not sure.

I have some videos from a cockpit mounted camera behind me early on... I will dig them out and see if it can reveal anything.

I will look to getting a gauge to test - Do you already know of a solution that works, to save me the investigation on connections etc?

Thanks very much for your help!

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3 weeks 4 days ago #22690 by Roger Lee
Replied by Roger Lee on topic Oil Pressure Drop on Take-off - SOLVED!
If Bill's solution doesn't work try this.

If the oil pressure decreases every time you increase the throttle and goes back up when you reduce throttle replace or tighten the ground wire. I have seen a number of these. The first one I ever saw way back when took me a couple hours to troubleshoot. I finally took a jumper wire and bypassed the original ground wire and problem solved. If you have a poor ground the pressure will change.

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-574-1080 Home (TRY HOME FIRST)
520-349-7056 Cell

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3 weeks 4 days ago #22693 by Bill Hertzel
Replied by Bill Hertzel on topic Oil Pressure Drop on Take-off - SOLVED!

John_in_Aus wrote: ... I will look to getting a gauge to test - Do you already know of a solution that works, to save me the investigation on connections etc?


Well, there is good news and bad news.

The Good News is that a 70-100psi gauge is inexpensive and easy to come by.

The bad news is that the gauge will probably have a tapered 1/8" NPT Fitting. (Common in the U.S.)
and that the sensor you will be removing and the port on the Oil Pump is a Straight Threaded M10x1.

The two thread are very similar and will happily cross thread without much effort.
Don't do it though, or you will soon regret it

The Good News is that this is a common problem encountered in the automobile industry and an NPT to M10 adapter should be readily available Online or at any decent auto parts store.

If the gauges in OZ are already M10 then you are golden!

Bill Hertzel
Rotax 912is
North Ridgeville, OH, USA
whertzel1@yahoo.com
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3 weeks 3 days ago #22694 by John_in_Aus
Replied by John_in_Aus on topic Oil Pressure Drop on Take-off - SOLVED!
Thanks Guys,

I will look into it over the next couple of weeks. We are heading into Winter here too, so makes keeping the oil temp up difficult. I put tape over the cooler last year which seemed to help a little.

OK - Back to the ground.... Are we talking the ground wire on the back of the Gauge? Or a wire on the sender? Could someone please clarify?

Cheers
J

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3 weeks 3 days ago #22695 by Bill Hertzel
Replied by Bill Hertzel on topic Oil Pressure Drop on Take-off - SOLVED!

John_in_Aus wrote: ... Are we talking the ground wire on the back of the Gauge? Or a wire on the sender?


The answer is YES!

Both the Gauge and the Sender have ground connections. And they both need to be good.
The sender may be grounded in the engine compartment or, preferably, it may have the ground wire connected at the gauge.

Bill Hertzel
Rotax 912is
North Ridgeville, OH, USA
whertzel1@yahoo.com
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3 weeks 3 days ago #22696 by John_in_Aus
Replied by John_in_Aus on topic Oil Pressure Drop on Take-off - SOLVED!
OK Thanks Bill. I will check it out.

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3 weeks 1 day ago #22705 by amhst56@gmail.com
Replied by amhst56@gmail.com on topic Oil Pressure Drop on Take-off - SOLVED!
Had this same issue a few months ago.
The guys here help me solve it.

The low oil pressure on takeoff was due to a 5 in diameter bend that the last mechanic put in when he did the 5 year rubber. Previous owner Installed a thermostat which made a few spots pretty tight.

I recall a 8 inch diameter bent the minimum. The low on takeoff is probably something like that.

If your gauges are good, think about the mushroom style oil regulator, new spring and bolt for the low pressure other than takeoff.

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3 weeks 1 day ago #22707 by John_in_Aus
Replied by John_in_Aus on topic Oil Pressure Drop on Take-off - SOLVED!
That’s interesting as it’s not long had the rubber replacement. Do you know where in the system?

I will trace all of the lines and check it out.

Cheers
John

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1 week 2 days ago #22816 by John_in_Aus
Replied by John_in_Aus on topic Oil Pressure Drop on Take-off - SOLVED!
So this weekend I went to the airfield to do some work on the plane, and try and get to the bottom of the oil issue.

I checked all terminals and reseated them etc... still the same.

Here is what I found and a short video.

On cold start oil pressure hits about 80PSI and then when warmed up, and it drops to what looks to be about 40PSI.

Then when advanced to 3000RPM, the pressure drops. At take off (5500+) it drops even lower.

I might look to swap out the sensor first, and see what happens.

See below.

www.dropbox.com/s/5y57a6ny1rrsfsr/IMG_5039.m4v?dl=0

Cheers
John

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1 week 3 hours ago #22833 by John_in_Aus
Replied by John_in_Aus on topic Oil Pressure Drop on Take-off - SOLVED!
So I have solved the issues, and it was very simple.

I put a call into our local Rotax guy and had a chat to him. His first response was the pressure spring. So that was the first point of call.

I removed the old one, and noted that it was a good 3mm shorter (and a bit softer) than the old one, which is what my Rotax guy said I would find.

Replaced with new spring and sleeve, and now the oil pressure is perfect right through the operations.

PS - A small dip on take off is normal, according to Rotax. But now it stays in the green, and the dip is minimal.

Anyways... Happy!
Cheers
J
The following user(s) said Thank You: Gyrochook.

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