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budyerly(at)msn.com
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 Posted: Sun Jun 03, 2018 7:02 am Post subject: Gurgling (burping) |
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Jonathan,
It is not uncommon for the oil level in the tank to drain down overnight. Even on a new engine. The tank can drain into the crankcase two ways on a 912UL (S). If the tank is full, and the return line has oil in it, it siphons down into the crankcase until the siphon is broken. That is only a small amount of oil on the dipstick.
The other is through the feed line, through the oil cooler and into the oil pump. The oil pump has tight clearances, but thin oil will drain quite rapidly through the pump into the crankcase via the many feed passages. You are right, it could be a seal in the oil pump was not changed on your rebuild or the oil pump shaft has worn beyond limits (check service bulletin 912-032). This internal seal leak doesn’t show normally, until the oil pump case to pump seal begins to leak. The case to oil pump is just sealed with 515. This is an easy fix and all external and right up front for your mechanic. So Look.
On the other hand, you would have low oil pressure if your pressure relief spring/ball were stuck so I doubt that is a problem.
Lastly, if you have a feed oil line leak at the tank, or internal in the pump, air is introduced into your feed line to the oil pump. This prevents oil getting to the pump, but doesn’t really affect the burp. If your oil pressure comes up quickly and when you pull the plugs and spin the engine by hand, you get oil pressure, that is not a factor. That is a difficult issue to trace. The only way to check is try using light air pressure on the oil tank overflow / vent line and remove listen for the oil moving or remove the oil feed at the pump and check for air. I really doubt that is a problem.
Note:
I found Mobile one synthetic drained quickly and the Aeroshell Sport plus 4 less. I would not be concerned. BUT:
50 blades on a 912S is quite a lot of spinning. (Normal for my old 914.) If you pause on each compression, it should only be about 10 blades of spinning to get a gurgle, but that is only based on new (er) 912S engines. The 912 and 914 tend to take more spinning to the verge of a heart attack on mine.
Do check for static leaks on your fittings as a Rotax will not leak oil externally unless something is wrong. If you have oil anywhere on the outside of your engine, oil pump, gearbox, or oil cooler, please investigate and solve it. If all is high and dry, it is probably just that shaft oil seal on the oil pump is leaking internally. This is not a huge problem, but warrants checking.
Best Regards,
Bud Yerly
Sent from Mail<https://go.microsoft.com/fwlink/?LinkId=550986> for Windows 10
________________________________
From: owner-europa-list-server(at)matronics.com <owner-europa-list-server(at)matronics.com> on behalf of jonathanmilbank <jdmilbank(at)yahoo.co.uk>
Sent: Wednesday, May 30, 2018 5:53:47 PM
To: europa-list(at)matronics.com
Subject: Gurgling (burping)
My 912ULS engine has done 250 hours since complete strip-down and rebuild after I bought it from an acknowledged Rotax engine expert. The three others who share the Europa with me are all happy with how sweetly it runs. The compressions were measured very recently and are excellent (close to 200 psi). The oil pressure is good being in the vicinity of 4 bar. BUT....
Nine times out of ten the oil drains quickly (overnight) from the tank to a level below the flat on the dipstick. This wasn't always so and has become worse over time. It used to take about a dozen compressions done quite slowly to push the oil back into the tank, while these days it can often take 50 or more compressions. Why?
My supposition is that the oil escapes past the oil pump and the rate of escape depends on the position of the pump lobes when at rest. So if the oil pressure remains good in flight, what's changed? Perhaps the oil pressure relief valve is sticking in some way?
Your experience and knowledge of likely causes would be gratefully received
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JonathanMilbank
Joined: 14 Apr 2012
Posts: 394
Location: Aberdeen area
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| Posted: Sun Jun 03, 2018 10:46 am Post subject: Re: Gurgling (burping) |
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Bud,
The outside of my engine and the oil cooler and tank are all free from all traces of leaks and the new hoses fitted a year ago are tightly clamped, so no air leaks.
I've taken your advice and looked at Service Bulletin 912-032, so this is the avenue that I'm probably going to investigate. Thanks very much.
Best wishes,
Jonathan
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clivesutton
Joined: 23 Jan 2013
Posts: 187
Location: KENILWORTH
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| Posted: Wed Jun 13, 2018 9:53 am Post subject: Re: Gurgling (burping) |
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For what it's worth, I was shown a better way to burp the oil on a 912ULS by my inspector Toby Wilcox today. Instead of many rotations of the prop, just turn slowly until resistance is felt, and hold it there until the resistance goes away - then repeat as necessary.
The crankcase is pressurised by cylinder compressions leaking past the rings and into the crankcase, so this method not only avoids /reduces un-lubricated metal parts sliding against each other (such as e.g. cams) but it actually takes considerably less effort or time to 'burp' the dry sump oil back into the tank.
Try it!
Clive
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Duncan McFadyean
Joined: 18 Jan 2011
Posts: 224
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| Posted: Sat Jun 16, 2018 2:30 am Post subject: Gurgling (burping) |
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Jonathan,
How do you know that the oil is draining overnight? Do you check oil level immediately after last engine shutdown?
I ask because I find there is a net drain of oil (from the catch tank) during any prolonged idle (e.g of a few minutes, and including glide decents) where followed by shutdown. Alarmingly so on occasions (to below the minimum dipstick mark). Prolonged idle may sometimes be unavoidable during taxiing in traffic, or voluntary, such as when allowing exhaust valves/piston rings (and turbo?) to cool before shutdown.
Duncan McF.
From: owner-europa-list-server(at)matronics.com <owner-europa-list-server(at)matronics.com> on behalf of jonathanmilbank <jdmilbank(at)yahoo.co.uk>
Sent: Wednesday, May 30, 2018 5:53:47 PM
To: europa-list(at)matronics.com
Subject: Gurgling (burping)
--> Europa-List message posted by: "jonathanmilbank" <jdmilbank(at)yahoo.co.uk>
My 912ULS engine has done 250 hours since complete strip-down and rebuild after I bought it from an acknowledged Rotax engine expert. The three others who share the Europa with me are all happy with how sweetly it runs. The compressions were measured very recently and are excellent (close to 200 psi). The oil pressure is good being in the vicinity of 4 bar. BUT....
Nine times out of ten the oil drains quickly (overnight) from the tank to a level below the flat on the dipstick. This wasn't always so and has become worse over time. It used to take about a dozen compressions done quite slowly to push the oil back into the tank, while these days it can often take 50 or more compressions. Why?
My supposition is that the oil escapes past the oil pump and the rate of escape depends on the position of the pump lobes when at rest. So if the oil pressure remains good in flight, what's changed? Perhaps the oil pressure relief valve is sticking in some way?
Your experience and knowledge of likely causes would be gratefully received.
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Burrilla
Joined: 25 Apr 2015
Posts: 187
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| Posted: Sat Jun 16, 2018 3:14 am Post subject: Gurgling (burping) |
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I assume that you are following SI-27-1997 on checking the oils level.
Personally I check after flight, I let the engine cool a little first, and that usually results in the “gurgle” after only a few blades. I also check before flight when engine cold but if I’ve done it after flight the check, when cold, only needs a few blades as all the oil has already been returned to the tank. Never had oil draining from the tank back into the engine.
I have found cold engines will take 10 or 12 blades, sometime more, to get the gurgle and this is often when I’ve hired something Rotax and the previous user has not done it warm.
Alan
G-OBJT
Sent from my iPad
On 16 Jun 2018, at 11:30, "ami-mcfadyean(at)talktalk.net (ami-mcfadyean(at)talktalk.net)" <ami-mcfadyean(at)talktalk.net (ami-mcfadyean(at)talktalk.net)> wrote:
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Burrilla
Joined: 25 Apr 2015
Posts: 187
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| Posted: Sat Jun 16, 2018 4:44 am Post subject: Gurgling (burping) |
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| Quote: | >I find there is a net drain of oil (from the catch tank) during any prolonged idle (e.g of a few minutes, and including glide decents) where followed by shutdown. Alarmingly so on occasions (to below the minimum dipstick mark). <<
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The max - min marks in the dipstick only have meaning after the gurgling process in SI-27-1997 are you doing that first?
Alan
G-OBJT
Sent from my iPad
On 16 Jun 2018, at 12:14, Alan Burrill <alanb(at)dpy01.co.uk (alanb(at)dpy01.co.uk)> wrote:
| Quote: | I assume that you are following SI-27-1997 on checking the oils level.
Personally I check after flight, I let the engine cool a little first, and that usually results in the “gurgle” after only a few blades. I also check before flight when engine cold but if I’ve done it after flight the check, when cold, only needs a few blades as all the oil has already been returned to the tank. Never had oil draining from the tank back into the engine.
I have found cold engines will take 10 or 12 blades, sometime more, to get the gurgle and this is often when I’ve hired something Rotax and the previous user has not done it warm.
Alan
G-OBJT
Sent from my iPad
On 16 Jun 2018, at 11:30, "ami-mcfadyean(at)talktalk.net (ami-mcfadyean(at)talktalk.net)" <ami-mcfadyean(at)talktalk.net (ami-mcfadyean(at)talktalk.net)> wrote:
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Duncan McFadyean
Joined: 18 Jan 2011
Posts: 224
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| Posted: Sun Jun 17, 2018 1:21 am Post subject: Gurgling (burping) |
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Alan,
I think you've missed my point, which was about how far the oil can drain down during certain aspects of normal use. Of course there is a procedure to follow for reinstating oil to the tank to be able to accurately confirm that sufficient total quantity of oil is present.
The later dipsticks provide for a greater quantity of oil than the early versions, probably in response to this in-use 'drainage' issue and to reduce the danger of the oil circuit becoming unprimed.
Note also that the UL Power engines now need a greater quantity to prevent oil starvation during aerobatics; similar sort of issue.
Duncna McF.
----Original Message----
From: alanb(at)dpy01.co.uk
Date: 16/06/2018 13:44
To: <europa-list(at)matronics.com>
Subj: Re: Gurgling (burping)
| Quote: | >I find there is a net drain of oil (from the catch tank) during any prolonged idle (e.g of a few minutes, and including glide decents) where followed by shutdown. Alarmingly so on occasions (to below the minimum dipstick mark). <<
The max - min marks in the dipstick only have meaning after the gurgling process in SI-27-1997 are you doing that first?
|
AlanG-OBJT
Sent from my iPad
On 16 Jun 2018, at 12:14, Alan Burrill <alanb(at)dpy01.co.uk> wrote:
I assume that you are following SI-27-1997 on checking the oils level.
Personally I check after flight, I let the engine cool a little first, and that usually results in the “gurgle” after only a few blades. I also check before flight when engine cold but if I’ve done it after flight the check, when cold, only needs a few blades as all the oil has already been returned to the tank. Never had oil draining from the tank back into the engine.
I have found cold engines will take 10 or 12 blades, sometime more, to get the gurgle and this is often when I’ve hired something Rotax and the previous user has not done it warm.
AlanG-OBJT
Sent from my iPad
On 16 Jun 2018, at 11:30, "ami-mcfadyean(at)talktalk.net" <ami-mcfadyean(at)talktalk.net> wrote:
Jonathan,How do you know that the oil is draining overnight? Do you check oil level immediately after last engine shutdown?I ask because I find there is a net drain of oil (from the catch tank) during any prolonged idle (e.g of a few minutes, and including glide decents) where followed by shutdown. Alarmingly so on occasions (to below the minimum dipstick mark). Prolonged idle may sometimes be unavoidable during taxiing in traffic, or voluntary, such as when allowing exhaust valves/piston rings (and turbo?) to cool before shutdown.
Duncan McF.
From: owner-europa-list-server(at)matronics.com <owner-europa-list-server(at)matronics.com> on behalf of jonathanmilbank <jdmilbank(at)yahoo.co.uk>
Sent: Wednesday, May 30, 2018 5:53:47 PM
To: europa-list(at)matronics.com
Subject: Gurgling (burping)
My 912ULS engine has done 250 hours since complete strip-down and rebuild after I bought it from an acknowledged Rotax engine expert. The three others who share the Europa with me are all happy with how sweetly it runs. The compressions were measured very recently
and are excellent (close to 200 psi). The oil pressure is good being in the vicinity of 4 bar. BUT....
Nine times out of ten the oil drains quickly (overnight) from the tank to a level below the flat on the dipstick. This wasn't always so and has become worse over time. It used to take about a dozen compressions done quite slowly to push the oil back into the
tank, while these days it can often take 50 or more compressions. Why?
My supposition is that the oil escapes past the oil pump and the rate of escape depends on the position of the pump lobes when at rest. So if the oil pressure remains good in flight, what's changed? Perhaps the oil pressure relief valve is sticking in some
way?
Your experience and knowledge of likely causes would be gratefully received
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