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We own 2 MTO Sport Gyrocopters in our flying school
in Queensland Australia.
As each engine has approached the 250 hr mark the oil pressure has reduced from approximately 3.5 bar to just over 2 bar. When attempting to address this situation with number one 912 (now at 550 hrs) the Australian Rotax importer sold me an extra shim and spring for the pressure regulator and explained how this magic will fix the problem, but the oil pressure has yet to increase to above 2 bar. Our second 912 (now 250 hrs) is doing exactly the same thing. We have yet to attach a steam powered pressure gauge, but thought I might as well ask the question.
Any help appreciated, Regards Don Cramer.
First thing is do not add any more shims under the oil pressure spring. You may take your real oil pressure way over the max and not even know. One tattle tail warning sign was you added a shim and saw no change.It should have made a 5-7 psi difference. Your Rotax person there gave you some incomplete info and you may cause harm. Many Rotax oil pressure senders weaken with time and vibration. Very first thing to do is verify whether you really have a low oil pressure or are you getting a false reading. Usually 98% of the time it is a bad reading. Most don't verify the real oil pressure and just throw things at the problem without doing a proper diagnosis. You need to put a mechanical pressure gauge in line with your existing oil pressure line. The cost of materials for a simple 0-100 psi gauge, some 1/16th copper tubing, a tee fitting so you can put your oil pressure sender back in line and some compression fittings is only about $20. I'm willing to bet you don't find you have an oil pressure problem as the Rotax 912 is very reliable and you find it is something else like the pressure sender (#1 problem usually) or even your gauge (not as likely).
I have seen this problem more times than I can count over the years and not once was it a real oil pressure problem, but an accessory problem like the sender or gauge and even bad ground connections.
You can also try these new parts from Rotax. It is a ten minute change and may help as it has others. You may not see a change with these either because if it is a sender issue then these parts won't help, but I would recommend these parts to be changed anyway after the problem is found. These new parts will help steady and possibly raise you pressure a little. Do the in line pressure check no matter what and don't do anything else until it is done. You are only working blind until you know something for sure.
Rotax parts: plug screw 841-983, Spring 838-122, and oil pressure regulator cone 857-230
1/8 npt is correct. If the problem does turn out to be the sender, you can increase their lifespan by mounting them remotely. Mounted to the firewall or frame, they are not subjected to engine vibration.
All sensors don't work with all meters. The sensor output must be compatible with the meter. If you just want to verify your present meter reading, the best way is as Roger suggested. Use a mechanical gauge. With enough tubing, you can temporarily mount the gauge in the cockpit and watch both gauges as you fly.
The oil pressure sender thread is M10x1 on the newer engines and NOT 1/8' NPT.
Make sure you stick to the same type of sender.
If you try and fit the wrong one, you will damage the oil pump housing and you could get oil leaking or worse, if you strip the thread, you will need a new oil pump housing.
Make sure you fit the right one.
What is newer engine?
Which serial numbers of 912ULS has M10x1 and which have 1/8" NPT?
MARK JACKSON wrote:
Is that correct?
It says that the type part no 456180 replaces the old 956413.
That means they have to have the same thread.
Can someone clear this problem? Which have M10x1 and which have 1/8" NPT?
Rob Seaton wrote:
465180 has metric M10x1 threads.
all the old sensors including the honeywell and VDO had 1/8NPT.
If you need to install a new 465180 sensor you can tap your old oil pump housing to cut new M10x1 threads.
Having straight threads allows the sensor to contact the housing; this greatly reduces the G forces (vibration) on the sensor.
I still prefer to remote mount the sensor.
I have now read the text again in this service instruction. The oil pump housing in todays engines has part number 911 815 and is for M10x1 thread for the sensor. The text also says that this house has been used for an earlier sensor 956 413. That means that sensor also has M10x1.
The earlier house 811 809 had a thread 1/8" NPT.
Now I wounder, what year (or better serial number)was the new house for sensor with M10x1 introduced?
Rob Seaton wrote:
Either look at the information on SI-912-020 R6 section 79-00-00. and see if your engine is one of the new ones, or unscrew the sender from the oil pump housing and measure the diameter of the thread.
If it it the new type of sender the it will be M10, if it is a VDO or Honeywell sender with flying leads then it will be 1/8 NPT
After control the house had part no 911815 so that means it's for M10x1.
It's not so easy to measure the the thread and fins out what it is (I think). Bye mistake I mounted a 1/8 NFT and it was possible to do it. So the difference is not big between the two.
Today I have found an adapter M10x1 to 1/8" NFT, so with that you can mount an 1/8 sensor
If you look at the sender, an M10 thread will be straight like a bolt and a relatively fine thread. Yoiu can screw an M10 nut onto it to be sure. A 1/8 NPT will have a coarser thread and will be tapered rather than cylindrical.
Mark had the right info. It is in service letter #SI 912-020R6.
Look on the BOTTOM of the oil pump housing. Pay no attention to the numbers on the front cover of the housing.
If you have #911-815 or 911-810 engraved under there, it is threaded for an M10 sensor. If it is #810-809 or 811-809, it is 1/8 NPT.