Help with chronic issues on hydraulic flaps, 65 M20C…

[Weston]

Hello all.  For the past few years I have had intermittent issues with flaps on my 65 M20C.  

We have been in 2 different mechanic shops and worked on it countless hours at home.  A few years ago, the pump was serviced  at LASAR and seals replaced, pressure check normal on bench (sent there twice).  Most recently, we had big actuator leak.  That was replaced with a rebuilt actuator and flaps did not function well thereafter.  Replaced with a newer used pump.  We bled the system multiple times and tried to adjust, then replaced a fatigued spring at the ball valve.   Function was improved for a short time thereafter.  After a few weeks, regressed to a place where she was holding full flaps, but bleeding up at any partial flap position.  

At annual this year, we tried to flush and re-bleed the system.  Tried suction technique from the back, then pressure pod from the back - even positive pressure at the back and suction from the reservoir side.  We never felt as though we were able to get all air bubbles from the system…. When we would work the pump, we just kept getting more and more air.  In addition, even in the flaps down position, fluid will transit back to front at a similar rate to the flaps up position.  Currently, flaps will go down with a variable number of pumps (5-7) and will bleed up even from the full down position.  So now unsure if ball valve is not seating and/or if there is some leak in the system allowing ingress of air (although we dont see a significant visible outward hydraulic fluid leak).    

Is anyone pressure testing or vacuum testing this system to make sure not a small leak before just exhaustive bleeding?

Is there anyone with a deep love and expertise on these hydraulic systems in Florida area who’d be interested to have a crack at it?  

I know that previous threads have talked about the simplicity and beauty of this manual system, but I am getting frustrated enough with the chronic problems and lack of readily available parts, that also starting to entertain the idea of an electrical conversion.   Does anyone have experience or suggestions on a kit for conversion from hydraulic to electric?  

Many thanks in advance for any help!  

 

[Andy95W]

@Shadrach is our resident expert.

Edited September 26, 2024 by Andy95W

[Shadrach]

Hi @Weston,

Is this the same M20C that was at a repair station in West Palm Beach back in February? 

 

[Weston]

Yessir, same bird .  

[Shadrach]

3 hours ago, Weston said:

Yessir, same bird .  

I’m really sorry to learn that you’re still dealing with this.I am baffled. I sent them a working pump which they disassembled and then used parts from both the original pump in your plane and the one that I sent them to get what they told me was a working pump. I logged a few phone calls and several texts walking their tech through trouble shooting and bleeding. He told me the problem was sorted during our final conversation. 

There are two probable scenarios that explain the symptoms you are experiencing:

1) The hydraulic fluid is contaminated with debris that are preventing the check valves from sealing and fluid Is flowing the wrong direction through the check valves

2) all of the check valve seats need to be recoined to prevent fluid from backflowIng through the check valves.

The first thing I would do is tighten the retraction speed screw all the way down. If the flaps stay down under those circumstances, your problem is almost certainly with the retraction circuit valve. If they bleed back up, then fluid is flowing the wrong way through the pump check valves. Feel free to DM me. I am dismayed that you’re still dealing with this..