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another flap bleeding thread...


rbridges

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I guess my crankshaft seal leak has been fixed, so why not a new headache?  lol.  Just had o-rings replaced in master cylinder and now the flap actuator.  No leaks noted now, but air in the system seems to be an issue.  IA who has no mooney experience, but followed the manual and instructions from you guys, has spent lots of time trying to remove air.  BTW, the flaps worked 100% prior to the annual.  Just replaced o-rings b/c of leaks noted when belly pan dropped.

Symptoms:

brakes feel ok, but I know they're last to show signs.

flaps will not go down unless you pump rapidly many many times

flaps seem to hold when they go down.

handle will not hydrolock; even when all the way down, you can't get handle to lock or stick

I can push down on flaps manually.  I've never paid a lot of attention during preflight besides a slight push, but are you supposed to be able to push them down by hand?

When flying, I can't get the flaps to go down; wind keeps them pushed up.

 

Soooo, is it a matter of getting it to prime?  I've read a lot of threads, and people have mentioned the system is self bleeding.  Is this true?

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When I experienced the same effect, something was allowing air into the system... by leaking the oil out of the system...

The hydraulic fluid was drying up, sort of, on the belly panel below... after leaking out of the return lines(low pressure side)...

The hoses, if original will become bubbly and cracked and look pretty obvious about their desire to be replaced... modern low pressure brake fluid hose is a pretty low cost, quick fix...

The flaps first show signs of running out of fluid, the brakes will follow if continuing to be used enough...

Filling the hydraulic reservoir can restore the flap use in this case, the sooner you get to it, the easier it is to pseudo-automatically bleed the air bubbles out of the system... lots of pumping and operating the flaps manually from outside.....

PP thoughts only, not recommended....

Best regards,

-a-

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What does your Owners Manual say about pushing your flaps by hand? Mine are electric, and only appear in Section 3, Preflight as "Flap and Attach Point--CHECK". But I've been pushing on both during preflight forever, and rarely get 1/2" of motion. Maybe it's something I picked up at a MAPA PPP.

Edited by Hank
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While I'm not a Mooney owner (yet) or really know anything about the hydraulic flap system, I'm very familiar with automotive braking systems and general hydraulics.  Is it possible the o-ring in the master tore or broke during reassembly and you are getting blow by?  Not sure if that would cause a leak in the Mooney system but that can cause the symptom you are seeing if that happens on a brake master.

I could be out in left field on this but wanted to throw it out there.

-Steve

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4 minutes ago, Steve_B said:

While I'm not a Mooney owner (yet) or really know anything about the hydraulic flap system, I'm very familiar with automotive braking systems and general hydraulics.  Is it possible the o-ring in the master tore or broke during reassembly and you are getting blow by?  Not sure if that would cause a leak in the Mooney system but that can cause the symptom you are seeing if that happens on a brake master.

I could be out in left field on this but wanted to throw it out there.

-Steve

Wouldn't that cause fluid to leak?  My IA thinks air is getting in, but I'm thinking some was left in after bleeding. I'm not a mechanic, but I don't know how air would get in without fluid blowing out somewhere. 

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Ooooh...

There are these tiny ball bearings in the system and a spring... that when properly installed act as a one way valve....

Those balls have a tendency to bounce.... far and wide.... while heading toward a floor drain... (quick owners, fleet of foot, don’t allow the escape :))

Putting them back requires a technique of using a glue on the finger tip... (a dab of grease works magic)

I remember this from down deep for some reason...

The MM has some pics of the assembly, the small balls and springs...

See if your mechanic remembers any of these details.

Best regards,

-a-

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2 minutes ago, rbridges said:

Wouldn't that cause fluid to leak?  My IA thinks air is getting in, but I'm thinking some was left in after bleeding. I'm not a mechanic, but I don't know how air would get in without fluid blowing out somewhere. 

Yes, it could cause a leak (I did say I wasn't sure if that would cause a leak in a Mooney system) but in some systems (again, not a Mooney) the blow by just goes back into the reservoir.

Given your symptoms, I would think there is a lot of air in the system though.

Since it worked before the reseal and it isn't now, I'd be inclined to go back and check what was changed (seals) provided you bled the snot out of it already (which it sounds like you did).

-Steve

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3 minutes ago, carusoam said:

Ooooh...

There are these tiny ball bearings in the system and a spring... that when properly installed act as a one way valve....

Those balls have a tendency to bounce.... far and wide.... while heading toward a floor drain... (quick owners, fleet of foot, don’t allow the escape :))

Putting them back requires a technique of using a glue on the finger tip... (a dab of grease works magic)

I remember this from down deep for some reason...

The MM has some pics of the assembly, the small balls and springs...

See if your mechanic remembers any of these details.

Best regards,

-a-

What he said.  I obviously have no idea what that system looks like and probably should have just stayed out of this thread.

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Steve,

Outside viewpoints are always appreciated...

Your input, reminded me of how an internal leak can be generated.

Of course, now i’m Having flashbacks of chasing a ball bearing across a cold concrete floor...  :)

Join the Mooney ownership tribe, no need to wait on this great experience!

Best regards,

-a-

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5 minutes ago, carusoam said:

Steve,

Outside viewpoints are always appreciated...

Your input, reminded me of how an internal leak can be generated.

Of course, now i’m Having flashbacks of chasing a ball bearing across a cold concrete floor...  :)

Join the Mooney ownership tribe, no need to wait on this great experience!

Best regards,

-a-

I once lost one of those balls in a utility sink. On top of rebuilding the flap pump, I had to remove the sink’s gooseneck. It was corroded and broke apart. I felt like Charlie Brown...but I got the ball back.

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6 minutes ago, carusoam said:

Steve,

Outside viewpoints are always appreciated...

Your input, reminded me of how an internal leak can be generated.

Of course, now i’m Having flashbacks of chasing a ball bearing across a cold concrete floor...  :)

Join the Mooney ownership tribe, no need to wait on this great experience!

Best regards,

-a-

Thanks. Looking forward to joining the tribe.  I'm in the hunt for one right now. 

-Steve

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27 minutes ago, Steve_B said:

What he said.  I obviously have no idea what that system looks like and probably should have just stayed out of this thread.

absolutely not.  I appreciate the input.  I'm thinking along your lines, but we're baffled, too.  

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Did your mechanic rebuild the pump unit, the slave cylinder at the flaps, or both?

The extra pumping before movement sounds like air in the system.  About 20-25 extensions/retractions, with a few minutes pause between each, will slowly get the air out- just as long as air isn't getting in, of course.

The other issues such as not locking in position, no hydrolock on the pump, and not extending in flight sounds like the slave cylinder back by the flaps has a bad o-ring or a definite air leak somewhere in the system.

Good luck.  You'll find the culprit eventually and get it working right.  Please keep us posted.

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4 minutes ago, Andy95W said:

Did your mechanic rebuild the pump unit, the slave cylinder at the flaps, or both?

The extra pumping before movement sounds like air in the system.  About 20-25 extensions/retractions, with a few minutes pause between each, will slowly get the air out- just as long as air isn't getting in, of course.

The other issues such as not locking in position, no hydrolock on the pump, and not extending in flight sounds like the slave cylinder back by the flaps has a bad o-ring or a definite air leak somewhere in the system.

Good luck.  You'll find the culprit eventually and get it working right.  Please keep us posted.

We changed o rings at the master cylinder and where the  pump handle engages underneath the plane.  afterwards we changed o rings in the actuator.  I keep leaning towards air in the system since everything was working fine prior to changing the o rings except for the small leaks that lead to the new o rings. 

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I was just going to go back and edit my post.  The 20-25 extensions and retractions will slowly get the air out of the pump only after the rear hydraulic cylinder has been bled per the maintenance manual and there is no air in that cylinder forward to the pump unit.

I hate to say it, but I would remove that rear cylinder and replace that o-ring again, make sure it's not rolled, re-install, and start the bleeding process again.  Should only take about 30 minutes and an o-ring for less than $1.

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Did anybody stretch the spring on the inlet ball? The spring pressure on that ball needs to be very light. It needs to be overcome by atmospheric pressure or the pump will cavitate. The maximum spring pressure is 0.18 lbs (2.88 oz) at sea level. 

When the pump cavitates the handle will spring back down after you raise it.

Don’t ask how I know.

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11 hours ago, Andy95W said:

The other issues such as not locking in position, no hydrolock on the pump, and not extending in flight sounds like the slave cylinder back by the flaps has a bad o-ring or a definite air leak somewhere in the system.

Good luck.  You'll find the culprit eventually and get it working right.  Please keep us posted.

This is why I think the pump was re-assembled incorrectly. I believe that one of the valves is reversed. As long as he pumps at a volume greater than the outflow the flaps will deploy. What is a mystery is the implication that the flaps stay down once deployed.

10 hours ago, N201MKTurbo said:

Did anybody stretch the spring on the inlet ball? The spring pressure on that ball needs to be very light. It needs to be overcome by atmospheric pressure or the pump will cavitate. The maximum spring pressure is 0.18 lbs (2.88 oz) at sea level. 

When the pump cavitates the handle will spring back down after you raise it.

Don’t ask how I know.

In my experience the symptom you describe is often caused by  The assembler incorrectly installing the ball valves. The pump then cavitates because the spring and ball are on the wrong side of the seat.  When this is done, trying to actuate the pump pulls the ball into the seat. I’ve never found spring tension to be an issue. I can’t imagine a scenario where are manually pumped hydraulic fluid couldn’t overcome one of those springs.

 

 Also it is good practice to lately stake each ball and seal (including the brass seat of the pump) before reassembly. I learned this the hard way. After reassembling the system correctly, The return valve (brass seat) would never completely seal. I had to remove the pump and remove the return valve tension spring and ball . There was no sign debris to be found nor any evidence of deformation of the seat. After like the staking the ball and seat everything worked perfectly.

Edited by Shadrach
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1 hour ago, Shadrach said:

 I can’t imagine a scenario where are manually pumped hydraulic fluid couldn’t overcome one of those springs.

When you raise the handle to draw fluid into the pump, it isn't hydraulic pressure from the pump drawing the fluid into the pump, it is atmospheric pressure. The lowest pressure you can create is a vacuum. With a vacuum on the pump side the pressure of the atmosphere (~15 PSI) pushes the fluid into the pump from the reservoir. This pressure differential can never be greater than atmospheric pressure. The port on the ball is approximately 1/8" which has an area of 0.012 Sq In. So the atmosphere can only push 2.88 OZ on that ball. If the spring pressure is greater than that the pressure will not be high enough to unseat the ball and the pump will form a void full of nothing (vacuum) which is cavitation.

Edited by N201MKTurbo
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27 minutes ago, N201MKTurbo said:

When you raise the handle to draw fluid into the pump, it isn't hydraulic pressure from the pump drawing the fluid into the pump, it is atmospheric pressure. The lowest pressure you can create is a vacuum. With a vacuum on the pump side the pressure of the atmosphere (~15 PSI) pushes the fluid into the pump from the reservoir. This pressure differential can never be greater than atmospheric pressure. The port on the ball is approximately 1/8" which has an area of 0.012 Sq In. So the atmosphere can only push 2.88 OZ on that ball. If the spring pressure is greater than that the pressure will not be high enough to unseat the ball and the pump will form a void full of nothing (vacuum) which is cavitation.

Thank you for the physics lesson Rich. Perhaps I should’ve been more specific. It’s my contention that there is no way that one of those springs could be made to withstand 14.6psi. Not going to happen.

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