912 Oil Pressure Sender leaking

[Friarpuk]

Hi folks

 

I have discovered on further investigation that the new pressure sensor is not leaking after all.

 

I have not realised that the thread is tapered and have put the new gauge in too far and split the housing.  Der to me 

 

So to get a new one costs about 900 from Floods. But I can get a secondhand one with the NPT thread for about half that from Floods.

 

I do feel like a twit.

 

Floods tell me I'm not the first to do this, but that doesn't make me feel any better.

 

An expensive lesson learnt.

 

Heath

 

 

[Thruster88]

Hi folks

 

I have discovered on further investigation that the new pressure sensor is not leaking after all.

 

I have not realised that the thread is tapered and have put the new gauge in too far and split the housing.  Der to me 

 

So to get a new one costs about 900 from Floods. But I can get a secondhand one with the NPT thread for about half that from Floods.

 

I do feel like a twit.

 

Floods tell me I'm not the first to do this, but that doesn't make me feel any better.

 

An expensive lesson learnt.

 

Heath

 

Don't worry you are not the first to do this, good advice in post #13 re tightening torque. My personal preference for thread sealing is any of the suitable Loctite products. 

 

 

[Blueadventures]

Hi folks

 

I have discovered on further investigation that the new pressure sensor is not leaking after all.

 

I have not realised that the thread is tapered and have put the new gauge in too far and split the housing.  Der to me 

 

So to get a new one costs about 900 from Floods. But I can get a secondhand one with the NPT thread for about half that from Floods.

 

I do feel like a twit.

 

Floods tell me I'm not the first to do this, but that doesn't make me feel any better.

 

An expensive lesson learnt.

 

Heath

 

Thanks for the heads up. Sorry to hear about the over tightening. Enjoy the next flight. Best thing is that you were not flying or even having a fire situation. Another example of the value of this site and the members helping out where possible.  Good info for 912 maintainers. Cheers

 

 

[skippydiesel]

Hi folks

 

I have discovered on further investigation that the new pressure sensor is not leaking after all.

 

I have not realised that the thread is tapered and have put the new gauge in too far and split the housing.  Der to me 

 

So to get a new one costs about 900 from Floods. But I can get a secondhand one with the NPT thread for about half that from Floods.

 

I do feel like a twit.

 

Floods tell me I'm not the first to do this, but that doesn't make me feel any better.

 

An expensive lesson learnt.

 

Heath

 

Hi Heath - have you found a definitive VDO Part No. ??

 

 

[onetrack]

Heath - The largest majority of pipe threads are tapered threads. If the pipe thread is parallel thread, it will have a sealing ring of some type - an o-ring, a copper or fibre washer, or a bonded washer.

 

https://www.adaptall.com/info-tutorials/sealing-methods.php

 

Generally, the important thing is ensuring you identify the thread correctly. Australian and British equipment uses mostly BSP pipe threads, but American-origin equipment utilises NPT threads. 

 

The awkward part is, a couple of the NPT threads are quite close to a couple of the BSP threads - but they are still not a good match, and screwing a BSP threaded fitting into a housing that has an NPT thread - and vice-versa - is a recipe for leaks and thread damage.

 

https://www.valvesonline.com.au/references/threads/

 

 

[Downunder]

The vdo (and honeywell) are a 1/8 npt x 27 tapered thread.

 

The Keller is a M10x1.0 as per the new oil pump housings.

 

I used an adapter (1/8 to M10) when replacing my honeywell to keller.

 

Rotax apparently authorise tapping out the 1/8 hole to m10 but I think that is wrong.

 

Physical sizes are similar and it is just a "butcher" job....

 

 

[skippydiesel]

Hay guys I did a lot of research on this a while back - if this is a Rotax 912/914,  pretty sure it will use either a 10mm parallel thread or a 1/8 NPT tapered thread.

 

They do "look" similar but the thread pitch is different and the use of a calliper will determine if the old sender is parallel or tapered - not too hard!

 

If the original sender is a  VDO,  it will have some information stamped onto the hexagonal/nut "base" - this information coupled with the observations above will determine which  replacement VDO sender is appropriate - not so hard if you take the time and care.

 

If you are concerned about overtightening - use either quality thread tape or Loctite products to ensure a seal and then hand tighten sender - place a hose clamp over the "body" and use safety wire to secure it in position (against rotation) - easy ! no problem !

 

 

[planedriver]

Over the many decades that I have been playing around with engines, iv'e had to replace quite a few, and had to do so on my own car this week. (Yes I know it's a Ford) , but quite often they are tucked up on the block under the manifold and more easily accessed if up on a ramp. The leak which often starts off as a small weep from the actual body, rather than the threaded part can progress to a more sinister leak which covers everything when subjected to heat, which makes it a bit harder to locate. Leaks from them is not uncommon at all. At least I didn't have to pay a Rotax price to replace mine. 

 

 

[skippydiesel]

...................... At least I didn't have to pay a Rotax price to replace mine. 

 

With a bit of research most if not all oil pressure senders (along with quite a few other parts) need not be sourced through Rotax (or agent)

 

 

[M61A1]

Ashdown Ingram....

 

https://view.publitas.com/ashdown-ingram/automotive-electrical-accessories-catalogue-2015/page/288-289

 

 

[skippydiesel]

Ashdown Ingram....

 

https://view.publitas.com/ashdown-ingram/automotive-electrical-accessories-catalogue-2015/page/288-289

 

Now that's a catalogue and a half,to drool over

 

 

[Friarpuk]

Ashdown Ingram....

 

https://view.publitas.com/ashdown-ingram/automotive-electrical-accessories-catalogue-2015/page/288-289

 

The 360.004 in this list is only 75psi where as the one I ordered from Aircraft Spruce was rated at 150psi.

 

 They have obviously changed in later products.  Floods quoted me on a 360.081 which I believe is 150psi.

 

Regards

 

Heath

 

 

[skippydiesel]

The 360.004 in this list is only 75psi where as the one I ordered from Aircraft Spruce was rated at 150psi.

 

 They have obviously changed in later products.  Floods quoted me on a 360.081 which I believe is 150psi.

 

Regards

 

Heath

 

I doubt you will need a sender rated to 150 psi - the Rotax 912/914 have very low pressure engine oil systems 

 

 

 

[IBob]

Yes, but the span of the sender....in this case 0 to 150PSI....needs to be matched to the span of the gauge, or it will not read correctly.

 

And if Floods are quoting on the 0-150PSI sender, presumably that is the correct span. for the older VDO sender and gauge.

 

also

 

It is usual in practise to 'oversize' the span. This means that the sender (which is a diaphragm with some electronics attached to it) will be more robust, since the diaphragm is not being flexed near it's limit.

 

 

[IBob]

For anyone else who may have an interest:

 

The believe the span of the newer Honeywell/Keller Rotax sender and gauge is 4 to 20mA = 0 to 10bar = 0 to 145PSI

 

What that means is that any 4-20mA sender with a span of 0 to 10bar (which is one of the common values) will do the job (provided it will stand up to the working environment.)

 

And any gauge that will show 4-20mA as 0 to 10bar or 0 to 145PSI will do (however there only seems to be the one in standard aircraft size).

 

And when you move to digital gauges, the span is less of an issue, since the gauge can usually be configured to accept and display what the sender is sending.

 

 

[skippydiesel]

Yes, but the span of the sender....in this case 0 to 150PSI....needs to be matched to the span of the gauge, or it will not read correctly.

 

And if Floods are quoting on the 0-150PSI sender, presumably that is the correct span. for the older VDO sender and gauge.

 

also

 

It is usual in practise to 'oversize' the span. This means that the sender (which is a diaphragm with some electronics attached to it) will be more robust, since the diaphragm is not being flexed near it's limit.

 

I have always applied the concept  - if the sender & gauge operate to at least twice the required pressure (or whatever value you are measuring) the system will be working in its mid range. This not only means it is more than up to the job but is likely to be indicating at its most accurate position.

 

I still find it strange that you are all so "wedded" to VDO (& similar high priced gauges) when Speco (7 others) offer a very robust Gauge & Sender that can be had for less than a VDO sender.

 

 

Plus sender about $60 or so.

 

 

[skippydiesel]

If you like or can only afford "steam gauges"  - Check this out as a cost effective alternative to VDO et al

 

http://www.speco.com.au/gauges_ss.html

 

Note: Speco senders are not compatible with VDO & visa versa

 

 

[Downunder]

I'm hitting 75 psi when very cold on start up, so a 75 psi sender will be at it's limit.

 

 

[skippydiesel]

I'm hitting 75 psi when very cold on start up, so a 75 psi sender will be at it's limit.

 

You may be  - momentarily when oil cold/thick - however this is nowhere near the normal operating range. Your normal range, at and above 3500 rpm, is between 29-72 psi. Minimum below 3500 rpm is a staggeringly low 11.6 psi. The Speco  will measure your normal running oil pressure (no problem), which you should note. Any significant deviation from this (during flight) may indicate, cooling engine at decent power, hot engine at  prolonged climb power, gauge/sender malfunction or a problem with the engine - LAND ASAP.

 

Oil pressure and temperature should be read together, along with what are you asking of the engine (climb, cruiz, decent power) for an informed understanding of what is happening.- - so know your normal temperature readings at the 3 stages of flight.

 

On two occasions I have felt hat my gauge was indicating outside my accepted parameters - on both occasions using a "master" gauge, I was reassured that the engines actual oil pressure was within Rotax specifications. The first time it was my lack of familiarity with the 912 engine the second (years later) a faulty oil pressure sender.

 

 

[Friarpuk]

All you folk will be happy to know that I have put the old girl back together and all is running well with no oil spewing out of the engine.  Had a "fun" time yesterday washing all the oil off the under side of my plane after plenty of test running. 

 

 

[skippydiesel]

Great news - very satisfying. What Gauge/sender did you install??

 

 

[Friarpuk]

I ended up putting a VDO gauge back in.  Went for a 1.5 hr fly this afternoon, and yes very satisfying.

 

 

[Garry_Smith]

Hi folks 

 

Have been trolling around in the threads and seen plenty about 912 oil pressure senders not sending the right info to the gauge.  

 

However my question is, has anyone had a sensor that has begun to leak.  I think mine is leaking a bit of oil, although it is had to discern exactly where it is coming from as it get blown around a bit.

 

Thoughts....?

 

Hi FriarPuk, I had this happen with my Rotax, I noticed it on after 30 hours on the motor, I replaced the pump. Cheers Gyro

 

 

[skippydiesel]

Hi FriarPuk, I had this happen with my Rotax, I noticed it on after 30 hours on the motor, I replaced the pump. Cheers Gyro

 

 

 

Me thinks you could expand on this a tad more (leaking oil pressure sender resulted in a replacement pump ??)