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Severe Jittering Oil Pressure

  • Alex Erdelyi
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1 year 6 months ago #11750 by Alex Erdelyi
I have been flying my Van's RV-12 ELSA since May of this year. The power plant is a 912
ULS. Since day one, I had noticed that my oil pressure had significant fluctuations (jitter), but
only after the oil had warmed up to operating temperature. When cold, the pressure is
rock solid.

Because I had some unrelated teething problems with the Dynon Skyview (a
defective SSD), I decided to add a backup mechanical oil pressure gauge (in parallel) in
case the Dynon were to fail while I was on a x-country trip. I wanted at least some
insight into what the engine was doing in the potential absence of the Skyview.
The installation of the mechanical gauge confirmed my jittering oil pressure issue and
that it was not caused by the transducer or the Skyview. The jittering was so bad (+-20
lbs) that it was impossible to read the mechanical gauge with any accuracy.

After doing some research on the issue, I discovered that Rotax had a replacement for the
steel ball in the oil pressure relief valve that was supposed to address this issue. It
is a "mushroom valve", that has a stem which helps guide the valve properly and eliminate
the bouncing oil pressure. I installed it at 30 hours of engine time, and sure enough,
the problem was immediately resolved.

That fix lasted about 25 hours, but the problem has now come back just as bad as before.
I pulled the mushroom valve out of the regulator only to find it was badly galled on the
stem. The spring had also galled the inside if the screw plug. Obviously, it had beating
itself to death from the constant chattering.

This is basically a new engine with about 55 hours of total time. It originally came with
the new type plug screw (part 841-983), but with a steel ball instead of the mushroom
valve. From what I understand, this is the way they are shipped currently.

I am now very concerned about the possibility of metal traveling through my engine as a
result of the galled oil relief valve parts. A week ago Monday, I enlisted the help of
Southland Rotax (F70) to try to get some answers regarding possible causes from the Rotax
mother ship. We filled out the Rotax CSIR form and sent it off through CPS with email
pictures attached. To date, we have not heard anything back from Rotax.

I'm curious if anyone in the group has experienced this problem and what the cause and
long term fix was. Also, please provide some input into how I can get some attention from
Rotax. My airplane has been down now for over a week now. Thanks in advance for your
input.

Alex

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1 year 6 months ago #11760 by Rob Seaton
Remember the oil pump sucks the oil from the oil tank so any restriction will cause surge/fluctuation.
-It could be you have a collapsing oil hose; make sure you don't have any kinks or flat spots in the hose. A kink will get worse when the oil heats up and softens the hose material.
-You also must use a suction rated oil hose but as you have a RV the correct hose would have came with the kit.
-Or a flap of rubber from a fitting installation?
The pump itself is pretty simple so the problem is most likely with the system. But if you cant find anything wrong then have CPS inspect the pump rotors, faceplate surface, drive pin, and pressure relief valve seat.It could be you had some FOD go through the pump damaging the faceplate running surface or rotors.

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  • Alex Erdelyi
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1 year 6 months ago #11776 by Alex Erdelyi
Thanks for your suggestions Rob. I heard back from Rotax. They suggested replacing the plug, spring and ball (instead of the mushroom valve) with new parts. I did that yesterday afternoon, and it test ran OK afterwards. Today I took a short flight and confirmed the problem is no longer there. What bothers me, the same thing happened after I installed the mushroom valve. Everything was great for a while, then it started the ugly behavior again after about 20 hours. I guess time will tell to see if its really fixed this time.

As for the oil lines, everything looks good and they are kink free. If the problem returns, I will tear all the hoses and pump off to look for damage or stuff floating around in the lines.

Thanks again,
Alex

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1 year 6 months ago #11799 by Paul Hamilton
Have always noticed a jitter in oil pressure with factory new S-LSA to now 300 hour 912ULS from 40 to 60 PSI. Figured it was typical for engine but will look and evaluate. Oil filter and magnetic plus always looked good.

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1 year 5 months ago #11801 by Rhett Mitchell
Mine is a bit jittery at idle and lower Rpm, but smooths out in flight.

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1 year 5 months ago #11835 by Paul Hamilton
Rock solid at startup 75 PSI but only gets gittery as the engine warms up. HUH.......

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  • Roger Lee
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1 year 5 months ago - 1 year 5 months ago #11836 by Roger Lee
75 psi is high and may not be real. Normal for most folks is 40-55 psi. Volume is important and high psi isn't.

Just a few items to check and rule out.
If mine was jittery I would first put a mechanical gauge inline to see if it was real. Then bypass my installed ground wire and install a direct ground to the gauge from the battery just for a run up check to see if it is still jittery, swap the sender out and or replace the oil pressure regulator ball bearing or mushroom and spring with new ones.

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-574-1080 Home (TRY HOME FIRST)
520-349-7056 Cell
Last Edit: 1 year 5 months ago by Roger Lee.

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  • Alex Erdelyi
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1 year 5 months ago #11915 by Alex Erdelyi
Roger,
My oil pressure also runs around 75lbs when cold. Drops to around 55-60lbs when oil is hot. Both my mechanical and elecronic gauges indicate the same. I had the same behavior as Paul. Pressure solid when oil is cold, but it jitters when oil is at normal operating temperature. Jittering was reduced to a tolerable level after I replaced the ball, spring and plug. I'm not convinced its fixed, since that is what I did the last time to fix the issue, but it came back after about 25 hours. I guess time will tell.
Alex

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1 year 5 months ago #11916 by Roger Lee
On first cold starts sometimes the oil pressure can pop up higher than normal like your 75, but should drop down as yours does as it warms up.

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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4 months 1 day ago #14918 by David Bird
Had an oil pressure issue a few days ago that had me scratching my head, and after a bit of scrolling, found this thread.

Was cruising wen i noticed the oil pressure gauge on 0.
Thankfully i fly rotors, so it didnt take long to put down from 100' and shut off.
Checked everything i could in the middle of woop woop and found nothing unusual.
Started up and felt the oil line change temp so i know i at least had circulation.
Anyway, once i was home i found the vdo gauge to be ok, tryed 2 other identical vdo senders said no pressure, then a mechanical gauge indicated very irratic pressure.
Found this thread, arranged a mushroom and tryed it today.
Turns out, after a serious dummy spit, that the electric vdo gauges didnt respond coz there was a dead short in the lead.
VDO works now, as it has for thousands of hours.
Havent checked with the mechanical one yet, to see if the mushroom did the trick, BUT, it begs the question, how many 9## rotaxs are happily flyn round with wild, rapid oil pressure variations, that are averaged out with the use of electric VDO gauges?
And dose it matter?

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3 months 3 weeks ago #14954 by Alan Arnold
My oil pressure has been fluctuating somewhat with a high of 60 and a low of 20. I had replaced the plug screw with the new style last year. Today I took it apart again to check for debris and found none. What I did find, while looking at the exploded diagram, was no shim p/n 227 055, and a ball p/n 432 680, which I apparently should have replaced with the cone p/n 857 230.
Would this explain the fluctuations? I plan to order these parts Monday and not run the engine until I have installed them.

Also, there is no gasket but also no leak. Should some sort of sealant be used on the threads?

Thanks for your help.

Alan 912ULS 2006 700 hours

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  • Roger Lee
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3 months 3 weeks ago - 3 months 3 weeks ago #14960 by Roger Lee
Hi Alan,

Just replace the ball bearing with the little mushroom. I hope there is still a ball bearing in there? Do not use a shim. 99.9% of the time this isn't the problem and people watch what they think is low pressure on the cockpit gauge when it is really over pressured.
First if you have not replaced the sender do that. Absolutely put a wrench or screwdriver on all your grounds. It may be hand tight, but wrench lose. Poor grounds are famous for causing fluctuating oil pressures. Check the oil pressure wires themselves and make sure they are making a good connection right up to the gauge.

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-574-1080 Home (TRY HOME FIRST)
520-349-7056 Cell
Last Edit: 3 months 3 weeks ago by Roger Lee.

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3 months 3 weeks ago #14962 by Alan Arnold
Thank you Roger. Yes, the ball is there. I'll order parts Monday and check my wiring while waiting for some good weather.

Alan

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3 months 3 weeks ago - 3 months 3 weeks ago #14964 by Roger Lee
Hey Alan, just a thought;

When you replace the ball bearing with the mushroom make sure you replace the spring too. It's cheap enough. maybe you already did the spring as it should have been done with the new style plug screw.

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-574-1080 Home (TRY HOME FIRST)
520-349-7056 Cell
Last Edit: 3 months 3 weeks ago by Roger Lee.

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3 months 3 weeks ago #14966 by Alan Arnold
I did do the spring but I'll do it again.

Thanks,

Alan

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  • Michael Boyianzis
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3 months 2 weeks ago - 3 months 2 weeks ago #15001 by Michael Boyianzis
Hi,

I have the same issue :( on start up oil pressure is fine 3 bar (30-50psi) green give or take photo of my gauge below... the once warmed up it jitters unacceptably .... small clip also here below...

www.dropbox.com/s/mhic3xhnbr28gab/IMG_2795.mp4?dl=0


any suggestions please?

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Last Edit: 3 months 2 weeks ago by Michael Boyianzis. Reason: link attached

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  • Alex Erdelyi
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3 months 2 weeks ago - 3 months 2 weeks ago #15030 by Alex Erdelyi
Michael, I'm the original poster to this thread. My manual oil pressure gauge behaves just like the one on your video once the engine warms up. Just today, I replaced the pressure regulator parts (ball, spring and plug screw) for the fourth time on a 160 hour engine. As usual, it fixed the problem. Oil pressure readings are now rock solid. Based on past history, I expect this fix will last 25 to 50 hours before the jittering oil pressure problem returns. I filed another "on-line" problem report with Rotax. They really need to step up and find a solution to this ongoing problem.

Alex
Last Edit: 3 months 2 weeks ago by Alex Erdelyi.

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3 months 2 weeks ago #15031 by Roger Lee
Hi Alex,

You have some other issue going on. This isn't a repeat problem with the oil pressure plug screw, spring and mushroom.
have you replaced the old style oil pressure plug screw? If not that could be the problem. If you have did you repalce the ball bearing? If not you need to install the mushroom and toss the ball bearing. Once these are done then if this continues I would have a hard look at the pressure sender or gauge.

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 months 2 weeks ago #15032 by Roger Lee
Hi Alex,

You have some other issue going on. This isn't a repeat problem with the oil pressure plug screw, spring and mushroom.
have you replaced the old style oil pressure plug screw? If not that could be the problem. If you have did you replace the ball bearing? If not you need to install the mushroom and toss the ball bearing. Once these are done then if this continues I would have a hard look at the pressure sender or gauge.

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 months 2 weeks ago #15034 by Alan Arnold
Update.

I just changed to the mushroom, with a new spring, and a new pressure sensor. I also remotely mounted the sensor on the firewall, using a kit from Lockwood which includes an orifice. I couldn't fly because of weather/wind concerns, but the pressure was rock solid during warm up, starting out at 70 and dropping to 60 at 160 degrees CHT. It has never been this stable. I'm guessing the mushroom and orifice has something to do with that.

Alan 699.7 hrs, 10.5 years

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