Hey guys. I am having issues with oil pressure on my 80 Hp 912. the problems I'm having are way out of my league and Im completely exhausted for ideas.

would love some input from experienced rotax owners on what they feel the problem may be and/or what action I should take from here. I will be calling Rotax Australia on monday but Im super stumped. I typed up a rundown on whats been going on but feel free to ask any questions.


Before works

The electronic oil pressure gauge would typically run showing between 150 – 200 KPA (21.7-29 PSI). this is low however the previous owner told me they replaced the oil pressure sensor and not the gauge and they said this was as a result of the new sensor not being properly matched to the gauge and that the oil pressure was ok.

Works completed.


Following the issue with my muffler the following work was completed (note, the muffler was patched up for me to fly home and the oil pressure was fine then, the variations in oil pressure has arisen since the following works were completed)

1) new exhaust installed and mounted differently
2) Carbys balanced
3) oil and filter changed
4) new Oil hose installed between radiator and what I believe is the return (comes in right below the bleeder)
during the test flight the pressures seemed normal but after 10 – 15 minutes the oil pressure started to gradually decline showing on the electronic gauge as low as 100 KPA (14.5 PSI)

I was advised to try 1 of 2 things. Replace the bleeder spring and ball (was found not to be done from the original AD) and that the issue is likely electrical so try fitting a capillary gauge.

After replacement of bleeder

so the new bleed spring, ball and screw fitting were changed. We ran the motor after this and it showed on the electronic gauge around 220-250 KPA (31.9 – 36 PSI). However when I reved the engine it would increase directly proportionally with throttle to as high as 350 KPA (50.7 PSI)
I took it for a flight about the airport and a circuit but after a matter of minutes the oil pressure started dropping when at idle and got as low as showing 50 KPA (7.2 PSI), It had never come anywhere near that low before. I got it back on the ground ASAP and we fitted a capillary gauge.

at idle the capillary gauge showed 50 PSI however when I revved the engine it got as high as 90 PSI at 5000 RPM. It is worth noting though the from 5000 – 5600 RPM the Pressure didn’t change, it remained at 90 PSI. I havn’t taken it for another flight since in fear of doing damage.

Intended further works

Right now my only plan is to try another Capillary gauge to insure it isn’t faulty. With both the electronic and capillary gauge showing a fluctuation I know there is a problem there, the question is which one is showing the right range of fluctuation. If a second Capillary shows the same numbers I know the electronic gauge is definitely out of sink.

Man...could be many things but your description of what actually changed is pretty short:

Oil filter
Oil cooler hose
Oil pressure regulator

Aside from wild scenarios like metal in the filter or cooler causing blockage, this is more likely:

For pressure regulator/relief valve, I read this from a Google search:

...inspected the oil pump housing and found a discrepancy in the seat of the pressure relief valve as compared to a new one so they sent me a new one to try and glad to report a 90-95% improvement.instead of large fluctuations of between 20 and 60 psi i now have a small vibration type fluctuation of 2-4 psi which could be caused by an air bubble somewhere.

If you replaced that relief valve/regulator, the seat could be different compared to your old one.

Of course, you're basing this all on your oil pressure data from the instrument. You might need to get a manual diagnostic unit for a test run to make sure your data is good.

/mud slung at wall

They are frustrating little engines. We have one that hasn’t missed a lick, another that we have now had 3 sets of oversized cylinders on and still burns 2oz/hr. It also vibrates, which it has from day one. Sprung for a new gearbox and it has the short shaft instead of the long shaft that we need so it’s getting boxed up and sent back to CPS. And dual carbs....really people?

Sorry to all you Rotax disciples, just a little pissed still.

I'd just go fly it, but that's me. Sounds like a gauge problem. After 2300 trouble free hours I probably have TOO much confidence in the thing, I just change the oil, ignore half the stuff other 912 pilots obsess over, and the sucker runs fine.

My dad and I have owned 10 or 11 different aircraft over the years. The cowling has been off the one Rotax more than the rest combined.

gbflyer wrote:My dad and I have owned 10 or 11 different aircraft over the years. The cowling has been off the one Rotax more than the rest combined.

Has all that bitching and moaning been an effective diagnostic technique?

Zzz wrote:

gbflyer wrote:My dad and I have owned 10 or 11 different aircraft over the years. The cowling has been off the one Rotax more than the rest combined.

Has all that bitching and moaning been an effective diagnostic technique?

[emoji867]

gbflyer wrote:They are frustrating little engines. We have one that hasn’t missed a lick, another that we have now had 3 sets of oversized cylinders on and still burns 2oz/hr. It also vibrates, which it has from day one. Sprung for a new gearbox and it has the short shaft instead of the long shaft that we need so it’s getting boxed up and sent back to CPS. And dual carbs....really people?

Sorry to all you Rotax disciples, just a little pissed still.

I flew 14 hrs this weekend, and used about 8-10 ozs. The Zipper Big Bores use a bit of oil, thanks to the low friction rings I understand, FWIW. I use about 1 qt. between 50 hr oil changes. The stock engine used none, I never added any between changes anyway, starting out at the highest level, and at 50 hrs being at the lowest. But it wouldn't let me climb 2 or 300 FPM at 4500 RPM at 7500', the increased low end torque I get is worth adding a little oil. I hear the legacy aircraft engines use a bit, that true? I also averaged, once again, 3.2 GPH fuel burn. Hope you get it figured out Ken, hang in there, it's a great little engine. Remember, I was a VERY reluctant new member of the 912 Rotax club, but the thing won me over!

courierguy wrote:

gbflyer wrote:They are frustrating little engines. We have one that hasn’t missed a lick, another that we have now had 3 sets of oversized cylinders on and still burns 2oz/hr. It also vibrates, which it has from day one. Sprung for a new gearbox and it has the short shaft instead of the long shaft that we need so it’s getting boxed up and sent back to CPS. And dual carbs....really people?

Sorry to all you Rotax disciples, just a little pissed still.

I flew 14 hrs this weekend, and used about 8-10 ozs. The Zipper Big Bores use a bit of oil, thanks to the low friction rings I understand, FWIW. I use about 1 qt. between 50 hr oil changes. The stock engine used none, I never added any between changes anyway, starting out at the highest level, and at 50 hrs being at the lowest. But it wouldn't let me climb 2 or 300 FPM at 4500 RPM at 7500', the increased low end torque I get is worth adding a little oil. I hear the legacy aircraft engines use a bit, that true? I also averaged, once again, 3.2 GPH fuel burn. Hope you get it figured out Ken, hang in there, it's a great little engine. Remember, I was a VERY reluctant new member of the 912 Rotax club, but the thing won me over!

Ken is my dad. I think he is secretly happiest with the one that acts up. He likes to work on them. Since we spend lots of time over cold water, any discrepancy, possibly considered minor by others, is not let go. NASA would be proud of him[emoji1]. One may get me one day, but not for the lack of maintenance.

Sorry to the OP. Hope you get your oil pressure situation squared away. Ronnie Smith at SMLA is a very helpful resource for all things Rotax. He teaches the maintenance class that a lot of the Predator drone guys attend. Hard to reach but will call you back.

Justin, between you two, who holds the “Repairman Certificate(s)” for the RANS S7S COURIER that you and your father assembled? You guys really paid attention to detail, looks better than many certified aircraft. Thanks again for the MoGas!

8GCBC wrote:Justin, between you two, who holds the “Repairman Certificate(s)” for the RANS S7S COURIER that you and your father assembled? You guys really paid attention to detail, looks better than many certified aircraft. Thanks again for the MoGas!

I am the one who gets to sign the logbook, the old man is the one who has the Rotax cert.

We have AVGAS on the field now too. Good for that R44.

Hope someone can help Drifter with his oil pressure.

gbflyer wrote:

8GCBC wrote:Justin, between you two, who holds the “Repairman Certificate(s)” for the RANS S7S COURIER that you and your father assembled? You guys really paid attention to detail, looks better than many certified aircraft. Thanks again for the MoGas!

I am the one who gets to sign the logbook.

Then you have the perfect right to complain! She definitely flew good when I saw her, however!

Sorry Tim for the drift. I’m a thread drifter driver today.

I'm tempted to split this thread to a new one called "Mating dance of adult males with mutual love of hijacking threads."

Good example of the noise so many here complain about. If you can't answer someone's question, or provide actual on-topic insight, don't reply.

Sorry

I've always found useful, the forum on Rotax-Owner.com
https://www.rotax-owner.com/en/rotax-forum/index

Anyone can read and you can register and post a question. That's free. I find the "how to" videos to be well worth the $30 for a year. R-O helped me sort out some issues I had. Good luck.