1963 C Model flaps acting up

[bavareze]

Hello!

 

Flaps were fine for 8 years, then the plane sat for 6 months.  The fluid level is fine. 

 

Now it feels like the pump is not sucking fluid when raising the lever.  The lever is soft and wants to go back, almost like there would be vacuum inside the pump.  Then the flaps don't move down.

 

I went under the plane, bled the slave cylinder - no more air.

 

When I'm pressurizing the reservoir with a few PIS of air,  the pump is sucking fluid and the flaps work just fine.  But as soon as I release the pressure, the pump is again not working.

 

Any ideas?

[N201MKTurbo]

Did you take the pump apart? That is the symptom of the inlet check valve spring is too stiff. When you pull the handle up, it makes a vacuum in the cylinder. Atmospheric pressure has to push the fluid into the chamber. the ball seat is about 1/8 inch or about 1/64 of a sq inch. Atmospheric pressure is about 14 PSI, so it only pushes on the ball with .2 Lbs. If the spring is stiffer than that it won't open. If you put it back together with the springs in the wrong place it will do that.

[bavareze]

No. I never touched anything.  It's been sitting for 6 months, worked well before.  No mx at all inbetween.

[A64Pilot]

I’m going to guess the fluid has gummed up, flushing it may fix the problem, if not then I’d disassemble and clean the pump, but I’d try the flush first

[Kelpro999]

You might try adding a pound or two psi to the reservoir vent while slowly operating the pump.

[bavareze]

On 7/11/2023 at 1:00 AM, Kelpro999 said:

You might try adding a pound or two psi to the reservoir vent while slowly operating the pump.

so as soon as I add a few psi of pressure to the reservoir, the flaps operate normally.  But then they revert to inop as soon as there is no psi.

 

It just feels like the inflow valve won't open by itself.

[Kelpro999]

9 hours ago, bavareze said:

so as soon as I add a few psi of pressure to the reservoir, the flaps operate normally.  But then they revert to inop as soon as there is no psi.

 

It just feels like the inflow valve won't open by itself.

 I think we have the same plane right now. I’ve been doing some refurbishment for a while and my flaps are acting same but I’ve had the park brake valve & reservoir out. Do you have the maintenance manual? I think air was drawn in the cap to shaft seal on the first stroke so bleeding should fix it for now but replacing pump seals should help keep it that way. If I remember right there’s a specific way to bleed the flap system. I’m not near my manuals until tomorrow but someone may come along with info before then. 

[Kelpro999]

Searching through my manuals revealed how vague the information is. I remember reading it but was probably a Google search result. I’ll also be after mine before long .

[glbtrottr]

Ooooohhhhh.

I just rescued an M20E that was sitting for 12 years with the exact same symptoms. Ugh.

Bleeding the brakes? Hmmm…imagine some nice ectoplasmic mud colored oooze with the contingency of pudding. Once aaaaaall that crap was pushed out, the brake and flap system was clean….the flaps worked then. Now the brake cylinders needed overhauling but that was a different matter altogether…


Sent from my iPhone using Tapatalk

[N201MKTurbo]

38 minutes ago, glbtrottr said:

Ooooohhhhh.

I just rescued an M20E that was sitting for 12 years with the exact same symptoms. Ugh.

Bleeding the brakes? Hmmm…imagine some nice ectoplasmic mud colored oooze with the contingency of pudding. Once aaaaaall that crap was pushed out, the brake and flap system was clean….the flaps worked then. Now the brake cylinders needed overhauling but that was a different matter altogether…


Sent from my iPhone using Tapatalk

Damn cheap a$$ o-rings only last 40 years or so…

[Kelpro999]

55 minutes ago, glbtrottr said:

Ooooohhhhh.

I just rescued an M20E that was sitting for 12 years with the exact same symptoms. Ugh.

Bleeding the brakes? Hmmm…imagine some nice ectoplasmic mud colored oooze with the contingency of pudding. Once aaaaaall that crap was pushed out, the brake and flap system was clean….the flaps worked then. Now the brake cylinders needed overhauling but that was a different matter altogether…


Sent from my iPhone using Tapatalk

Same here.. some kind of caramel syrup paste in my brake side and pretty sure that’s what I’ll find in my flap side 

[DCarlton]

The brake fluid polymerizes to form the gel.  Doesn’t last forever.  Need a MS chemist to explain why.  Had my brakes lock up years ago for this reason.  

[M20F]

If you take it apart note which spring goes where.   The parts manual says they are the same but they are not.  One is strong and one is weak.  If you reverse them it doesn’t work.