914 oil/turbo issue.

birdy

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Gday crew, Iv had sum perplexing issues lately with a constant speed 914.
firstly, I received this machine 2nd hand with < 200 hours on the engine, and I don’t think the previous operator knew much about anythn mechanical.
Had no issues for the first 500 odd hours, cept for a slight oil weep from the cold side of the turbo.
then a few hours back I just happened to notice the oil pressure was off the dial???
quickly put it down, and as the rpm came down, so did the oil pressure. It sat at normal hot oil pressure at idle, and after checkn a few things I spun up to 100%, pressure still good so took off again. After a short while the pressure started to climb again, two steps forward, one step back, till it was off the dial again, so I made a dash for home.
pressure came down wen I reduced throttle as before.
not sure wot pressure it went to coz the vdo only go’s to 90odd psi and it went way past that.
anyway, abit of checking and it turned out the rotax recommended replacement relief valve ( mushroom shape replaced the ball) was sumhow jammen closed🤔🤔🤔, in flight. Coz the fix was to put the old ball back in, all normal again.
id pay handsomely to anyone who can give a credible explanation for how an oil relieve valve can slowly close while runin at a constant rpm.😂😂😂

second issue was the turbo started pumpin oil out both sides after the oil pressure issue.
sumthn went throo the scavenge pump rotor, from the turbo sump and scoured it badly, but after replacing with new rotor and body, the scavenge pump is workin as it should but oil was still leakin from both sides of the turbo.
report from the turbo doc was both bearings, shaft and seal in the turbo are rooted.
not sure wot the sequence was, turbo leaked oil, it burned and scoured the bit, or the bits failed and oil
Leaked, or sumthn dislodged from the turbo and stuffed everythn down stream of it, or the over pressurised oil system caused this chain reaction, or, or......
anyway, turbo is being rebuilt, so we will see wot happens next.

still like to no how the oil pressure went off?🤔
 

birdy

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Don't have an answer...just wanted to say it's good to see you back on the forum.

smiles,
Charles
Thort the info bout the pressure off tha dial fix may be of interest, as well as tryn to find out how/why it did.
 

schmoe90

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I know there's a section in the Magni maintenance manual about oil line coking on the 914 if it's running in a shrouded configuration, like an M-24 - that could affect pressures (and temperatures) methinks. I can look it up when I'm on the right computer :)
 

fara

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Your turbo oil reservoir line is blocked because of coked oil most likely. The oil is getting cooked way too much near the turbo or in the turbo oil reservoir. Check turbo seals also. Does this have an after-muffler on it by any chance? If so take that off and put it aside. They are not good for power nor for the engine. Only good for the neighbors. Always run the engine at idle till oil temp comes down before shutting the engine off
 

Smack

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Mr. Birdy, glad to hear from you after all this time.
I think Rotax mentioned that the SPRING begins to loose 'tension' over time and the spring must be replaced.
Did you use the same spring when you went back to the ball or did you replace the spring?
I think that they put out a service bulletin on this.
 

birdy

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Turbo is in free airflow, so heat is not an issue wen flying.
iv always run it down before shutoff, and the lines/sump/tank had 0 carbon.
if the spring lost tension, I’d loose pressure, not gain pressure.
 

Chook

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Gday Birdy.
I seem to recall one of these pressure regulator systems was wearing a groove in something (spring, side wall or regulator tube) which makes it stick. Pull it apart again and check the walls where the regulator pin or spring slides.

Regards......Chook.
 

wolfy

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Just thinking this morning, did this engine spend it's life on avgas before your time Birdy?
Led deposit's causing the sticking?

wolfy
 

birdy

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Not,
Was that engine factory with the new style mushroom pressure relief?

wolfy
no, rotax told me to change it.
The 912 still has the mushroom, but will be watching that one now.
 

birdy

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Alice Springs-central Oz.
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open frame single seat & a 'wasa' RAF, among other types.
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7000 odd, bout 5000 gyro
Gday Birdy.
I seem to recall one of these pressure regulator systems was wearing a groove in something (spring, side wall or regulator tube) which makes it stick. Pull it apart again and check the walls where the regulator pin or spring slides.

Regards......Chook.
Was a very slight grooves here it seats I could feel with the finger nail, but not visible, and I couldn’t make it wedge, gam or hydraulic in the banjo.🤔
and duno wolfy, but i recon not. I’d dun 500 odd hours onit before this ballsup.
 

Resasi

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Welcome back.
 

Eric S

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Turbo is in free airflow, so heat is not an issue wen flying.
iv always run it down before shutoff, and the lines/sump/tank had 0 carbon.
if the spring lost tension, I’d loose pressure, not gain pressure.
Any chance you switched to a different oil and the new oil can't handle the heat as well?
 

ventana7

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Your turbo oil reservoir line is blocked because of coked oil most likely. The oil is getting cooked way too much near the turbo or in the turbo oil reservoir. Check turbo seals also. Does this have an after-muffler on it by any chance? If so take that off and put it aside. They are not good for power nor for the engine. Only good for the neighbors. Always run the engine at idle till oil temp comes down before shutting the engine off
Birdy,

You need to keep that muffler on so you don't disturb your neighbors!!😂😂😂😂😂

I coked my turbo up once when I did not do a full 5 minute cooldown before shutting down the engine. The guys that did the turbo clean advised that I inlarge the drain tube from the turbo to the turbo oil sump as well which I did.
 
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