raizo

Well it,s been nearly a year since i last posted ,March last year,and sadly my pressure problem returned as bad as ever and not long after fitting the new oil housing about 5 hours of flying,For those of you not familiar with my problem my oil pressure fluctuated horribly between 30 and 80 psi so bad the needle on the manual gauge was a red blur, and the MGL gauge was unreadable, GOOD news is i posted this problem on the Rotax forum along with a fellow RV12 owner in the US with similar problems and a gentleman(a retired engineer ) in the US came up with the answer, he studied the problem for some time and lots of phone calls and emails later he had the solution,the problem arises when the mushroom valve is pushed back from its seated position and then in my case(and others) the head of the valve starts to bobble around(like one of those toy dogs with the wobble head) this is evident by the marks on the valve stem, The 912 IS has a different oil valve ,its a piston style so can only travel up and down and does not bobble about (it is also larger than the 912ul valve),so he manufactured a valve using the piston idea to suit the 912ul motor,myself and a gentleman in the US have been testing this valve as well as talking to the Rotax engineering department for the past 9 months and are VERY pleased to say ,i myself have over 70 hours of flight time with rock solid oil pressure and Alex in the US has 40 plus hours,so anyone with oil pressure problems ,we have the answer. If anyone is interested i can put you in contact with Bill in the US who came up with the solution ps this is still in testing phase but some more testers would be good,Rotax have shown great interest in the valve and are eagerly waiting for our results You can follow my,and Alex path on the Rotax owner forum ,search Sever jittering oil pressure and on page 5 is a link to the answer.

Latest news.,Bert Flood 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.

Have removed the oil pump housing and sent it of to Bert Flood for inspection,will keep you posted

HI all, a quick up date, I had also posted this thread on the Rotax owners forum, and just had a reply from a USA based Rotax mechanic who was dealing with the exact same problem on the same aircraft RV12 they tried exactly what I had done with the same results they then tried a borrowed oil pump housing and the problem went away so on further inspection of the old housing sever chaffing of the PRV seat was found, they then inspected 5 other housings and not one was chaffed, A fellow club member who has been helping me has offered his oil pump housing to try to see if this may be the problem, if so Mr Flood will be getting a phone call

Thanks for your comments everyone, Geoff, the PRV is located at the bottom of the oil pump and the mushroom is a replacement part for the normal ball and spring component of the PRV its suppose to eliminate the flutter problem but as I have discovered on the Rotax Owner forum it often does not get rid of the problem, as you pointed out it may not be seated properly ,as stated we changed all the oil lines so there is no obstruction there, will check the breather lines though will also check all fitting on the oil tank(may as well check everything) and yes we purged the system after replacing the oil lines.Our next step is to remove the pump and have it checked and maybe change back to the ball and spring????? As yet no reply from Bert Flood

Thanks for the reply Skippydiesel, I sent a rather long and descriptive email to Gary at Bert Floods last night(again) hoping they will respond with some positive action, stripping the motor is a drastic and costly measure if this has to be done I hope Rotax will cover the cost as the motor is out of warranty

Thanks Alf but we tried a new sender and then verified the problem by fitting a mechanical gauge which proved the readings we are getting from the sender, we have changed oil and filter 3 times so cant be the filter???? John

Short answer,NO replacing the collapsed oil line did not solve our problem,now at a total loss as to where to go next

an update to the original post,after a long investigation ,and by confirming fluctuations with a mechanical gauge,we are are no closer to solving the problem,we have fitted the new mushroom valve and spring,no change ,tried a new sender,no change,completely rewired the aircraft,no change,But today we found a collapsed oil line ,right where it enters the oil cooler,and after researching the web have found this may be our problem,so will order new oil hoses and fit this weekend,if this is not our problem will look at removing the oil pump,but as previously stated this has been a problem since we installed the 912 since new Will keep you posted

Thanks Scott,this has been a problem since the motor was new ,and has had 3 oil fliters ,i have a gentlemen coming this afternoon to check the electrical side of things ,as Matt fromm MGL seems to think this is where the problem is, Cheers John

I am experiencing very erratic oil pressure readings on my 912,it is fitted with the new style sender,and have fitted the new mushroom valve and spring, the pressure gauge is an MGL TP1 dual oil pressure and temperature type gauge. at low oil temperature from start up to app 55 degrees the pressure is fairly steady but once it has reached app.70 + the readings become VERY erratic,impossible to read. gauge is directly earthed to engine block ,oil temp. reading is steady .I think it may be an earth loop problem but the change from reasonable reading when cold to very erratic when hot is throwing me. Any suggestions would be appreciated. I have run this by the guys at Bert Flood and they are scratching their heads also.also MGL just tell me to check the earth which i have done Cheers John

Hi all! new throttle spring arrived from Vans today,there is a great deal of tension difference between the new and the original Rotax ones,happy to report that after a 45min flight ,happy to report no throttle creep at all,also it has made the throttle so much lighter as not as much friction nut is needed.also have attached the alternate fuel tank we made Cheers Raizo

Thanks rgmwa,the quote I god from Rod at Aircrfat spruce Australia (sky shop)lists the part number 6696 which if you check the McFarlane web site this number has been superseded by the 6822 number Raizo

Thanks rgmwa,i believe the ones I have ordered from Aircraft Spruce are the Mcfarlane springs, they are approx 3lb/in compared to the Rotax 8-10lb/in

Hi all,is anyone else experiencing throttle creep on their Rotax 912 ,I have the friction nut wound up very tight but still get creep,it seems to be a fairly common problem going by the Vans forums. I have ordered a set of throttle return springs with less tension than the Rotax ones from Aircraft Spruce,they should arrive next few weeks, Hopefully that will ease the problem Cheers Raizo