Oil Pressure Mushroom

H. Paul Shuch is a Light Sport Repairman with Maintenance ratings for airplanes, gliders, weight shift control, and powered parachutes, as well as an independent Rotax Maintenance Technician at the Heavy Maintenance level. He holds a PhD in Air Transportation Engineering from the University of California, and serves as Director of Maintenance for AvSport of Lock Haven.

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3Dreaming
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Re: Oil Pressure Mushroom

Postby 3Dreaming » Fri May 04, 2018 12:32 pm

It is easier to check the engine itself. If the cap has a recessed center it has the new style. If it is flat all the way across it is the old style.

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FastEddieB
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Re: Oil Pressure Mushroom

Postby FastEddieB » Fri May 04, 2018 6:39 pm

3Dreaming wrote:It is easier to check the engine itself. If the cap has a recessed center it has the new style. If it is flat all the way across it is the old style.


It's flat and Roger didn't note a change, so I'm ordering the parts tomorrow if they're open.
Fast Eddie B.
Sky Arrow 600 E-LSA • N467SA
CFI, CFII, CFIME
FastEddieB@mac.com

roger lee
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Re: Oil Pressure Mushroom

Postby roger lee » Sat May 05, 2018 8:14 am

The newer style mushroom is an option. Rotax still uses the ball bearing in new engines. Nothing wrong with changing the oil pressure plug screw, spring and mushroom. If you replace the plug the spring also needs to be replaced. If you just get rid of the ball bearing the spring needs to be replaced. If you are swapping out the old plug screw and want the mushroom replace all three parts.


Oil pressure shims should NEVER be used without a mechanical gauge confirmation of the true oil pressure. You almost never see a true low oil pressure. It is usually a bad sending unit, poor ground, reduced radius oil supply hose, wrong sensor type selected if you have a digital instrument or just a bad connection. These all must be ruled out first. I've had several come to the shop that swore it was low oil pressure. They put a shim in and then the pressure would be up in the 80's.

Mechanical gauge confirmation first is a must.
Roger Lee
Tucson, Az.
LSRM-A, Rotax Instructor & Rotax IRC
(520) 574-1080 (Home) Try Home First.
(520) 349-7056 (Cell)

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FastEddieB
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Re: Oil Pressure Mushroom

Postby FastEddieB » Sat May 05, 2018 8:58 am

roger lee wrote:The newer style mushroom is an option. Rotax still uses the ball bearing in new engines.


That surprises me.

Is there then a 1,500 hr TBO on a factory new engine until the ball bearing and associated parts are replaced?

Doesn’t make sense they would not ship engines without the latest parts. I wonder what the logic is.
Fast Eddie B.
Sky Arrow 600 E-LSA • N467SA
CFI, CFII, CFIME
FastEddieB@mac.com

3Dreaming
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Re: Oil Pressure Mushroom

Postby 3Dreaming » Sat May 05, 2018 9:09 am

FastEddieB wrote:
roger lee wrote:The newer style mushroom is an option. Rotax still uses the ball bearing in new engines.


That surprises me.

Is there then a 1,500 hr TBO on a factory new engine until the ball bearing and associated parts are replaced?

Doesn’t make sense they would not ship engines without the latest parts. I wonder what the logic is.


The ball is not required to be replaced as part of the upgrade to extend the TBO, it is optional if you have fluctuating oil pressure. IMO the swap out of parts is nothing more than a way to determine if the engine has the extended TBO.

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FastEddieB
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Re: Oil Pressure Mushroom

Postby FastEddieB » Sat May 05, 2018 9:32 am

Last two post definitely change my calculus.

Reconsidering spending $50 or $60 for no obvious benefit.

I was pretty sure I had read that part had to be replaced to extend the TBO.

This SB says at least the “plug screw” must be replaced.

https://legacy.rotaxowner.com/si_tb_info/serviceb/sb-912-057.pdf

I also found an old post of Roger’s on the ROTAX Owner’s forum that said all 3 parts must be replaced to extend the TBO.

https://www.rotax-owner.com/en/rotax-forum/3-4-stroke-technical-questions/3567-tbo-extension-clarification-please

Confusing.

Edited to add: I see Roger says in that same post that very little oil is lost, a no purge should be necessary if that’s all that’s done.
Fast Eddie B.
Sky Arrow 600 E-LSA • N467SA
CFI, CFII, CFIME
FastEddieB@mac.com

TimTaylor
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Re: Oil Pressure Mushroom

Postby TimTaylor » Sat May 05, 2018 11:49 am

I would just do it and not look back.
Commercial Pilot Airplane Single & Multiengine Land; Instrument Airplane; Sport Endorsement Airplane Single Engine Sea; Flight Instructor Airplane Single And Multiengine; Ground Instructor Advanced Instrument

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drseti
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Re: Oil Pressure Mushroom

Postby drseti » Sat May 05, 2018 4:02 pm

On every plane I've upgraded to the 2000 TBO, I replaced merely the spring and cap (not the ball). I've never found the mushroom to be necessary, although I do keep one in stock just in case. But it is important to check the engine s/n to see if it's eligible for the upgrade. (Anything with a crankcase s/n > 06.0010 should be.)
The opinions posted are those of one CFI, and do not necessarily represent the FAA or its lawyers.
Prof. H. Paul Shuch, Ph.D., CFII, LSRM-A/GL/WS/PPC, iRMT
AvSport of Lock Haven
fly@AvSport.org
http://AvSport.org
http://facebook.com/SportFlying

roger lee
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Re: Oil Pressure Mushroom

Postby roger lee » Sat May 05, 2018 4:46 pm

To extend TBO it's just the plug screw and spring. The mushroom is optional and no purge is necessary because of the tiny amount of oil lost. The ball bearing has been known to cause chattering and slight oil pressure fluctuations due to the rounded surface tension on the ball and its seat. The mushroom has a hole in it and a sharper curve plus the long stem to help hold the spring straight and not bend. The spring also was involved in oil fluctuation because with the old short plug screw because it would let the spring rub on the housing wall. If you want to keep the ball bearing no big sweat. Rotax years ago came out and said it was more concerned with volume over pressure. So I would rather see 45-50 psi over 65 psi. The way the plug screw, spring and ball bearing work is when oil is forced through the pump and on its way out the other side it creates a pressure. The spring is tensioned to maintain a certain pressure and when the pressure exceeds the outlet pressure the ball bearing / spring compress down and allow oil to go back into the inlet side of the pump. If there is a Rotax engine that needs a shim then you better confirm that with a separate mechanical gauge and better just fix the cause of the low pressure. I would consider something below 40 psi on every single flight something that should be looked at. 45+ psi is no big deal. Pressure is a range and not an absolute number.
Wrong oil types, reduced radius hose, reduced radius fittings, oil tank bottom plate upside down and low oil level can affect the pressure. Once in a great great while and oil pump has an issue.
Last edited by roger lee on Sat May 05, 2018 4:59 pm, edited 2 times in total.
Roger Lee
Tucson, Az.
LSRM-A, Rotax Instructor & Rotax IRC
(520) 574-1080 (Home) Try Home First.
(520) 349-7056 (Cell)

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FastEddieB
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Re: Oil Pressure Mushroom

Postby FastEddieB » Sat May 05, 2018 4:50 pm

I don’t have my engine serial # handy - will check when next at the hangar.

I read somewhere of there are no washers underneath the cylinder head bolts, it’s the new, eligible design. Mine does not have those washers, if that means anything.
Fast Eddie B.
Sky Arrow 600 E-LSA • N467SA
CFI, CFII, CFIME
FastEddieB@mac.com

roger lee
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Re: Oil Pressure Mushroom

Postby roger lee » Sun May 06, 2018 8:43 am

5648194, you're included for the TBO ext.

"https://legacy.rotaxowner.com/si_tb_info/serviceb/sb-912-057.pdf "
This is for certified engines.
You want SB-912-057UL for non certified engines.
Roger Lee
Tucson, Az.
LSRM-A, Rotax Instructor & Rotax IRC
(520) 574-1080 (Home) Try Home First.
(520) 349-7056 (Cell)

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FastEddieB
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Re: Oil Pressure Mushroom

Postby FastEddieB » Sun May 06, 2018 2:15 pm

roger lee wrote:5648194, you're included for the TBO ext.


Wow!

You must be psychic!!!

Image
Fast Eddie B.
Sky Arrow 600 E-LSA • N467SA
CFI, CFII, CFIME
FastEddieB@mac.com

3Dreaming
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Re: Oil Pressure Mushroom

Postby 3Dreaming » Sun May 06, 2018 3:33 pm

FastEddieB wrote:
roger lee wrote:5648194, you're included for the TBO ext.


Wow!

You must be psychic!!!

Image


The term my kids use is telepathetic. :D

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drseti
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Re: Oil Pressure Mushroom

Postby drseti » Sun May 06, 2018 3:44 pm

3Dreaming wrote:The term my kids use is telepathetic. :D


I knew you were going to say that!

Of course, if you really are, your kids don't have to use the term, just think it.
The opinions posted are those of one CFI, and do not necessarily represent the FAA or its lawyers.
Prof. H. Paul Shuch, Ph.D., CFII, LSRM-A/GL/WS/PPC, iRMT
AvSport of Lock Haven
fly@AvSport.org
http://AvSport.org
http://facebook.com/SportFlying


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