oil leaking from edo-aire prop governor

[Vance Harral]

Not a new topic and a few other threads open on this sort of thing, but one always craves input on their specific problem.

Below is a side view of the Edo-Aire 34828014 propeller governor installed in our 1976 Mooney M20F.  This governor was overhauled in October of 2005 on our watch, and has about 1150 tach hours time-in-service since then.  We don't have any operational problems with it - takeoff RPM is right at 2700 and it holds well with no hunting - but a recent investigation into oil leaks has established there is a significant leak at the seal pointed to by the red arrow.

It's tempting to start by applying a little extra torque to the mounting bolts to compress the seal, and see if that stops the leak.  But a lot of people pooh-pooh that approach, and with good reason - it's a band-aid at best (not to mention a real PITA to remove and re-do the safety wire).  The real question I have, though, is what's the nature of this seal?  Does one have to overhaul (or at least IRAN) the governor to replace it?  Looking at a picture of a used one for sale, it appears the interface where the oil is leaking doesn't simply come apart when the mounting bolts are removed, but rather is integral to an assembled unit.  So even if one was inclined to try extra torque on the mounting bolts, it's not clear to me that would actually compress the seal in question.

Second, if an overhaul/IRAN is warranted, I'd like to hear opinions on doing that vs. replacement.  I'm aware some owners here have replaced their "antique" Edo-Aire and Hartzell governors with a new PCU5000 or similar.  I'm also aware some shops won't work on these older governors, as we had to hunt around for a shop that would do so even in 2005.  But honestly, the Edo-Aire unit has served the airplane well for decades, is working fine at the moment aside from the leak, and the benefit of replacing it with a "new" design is unclear.  What say you?

 

[carusoam]

Looks to me, a mere PP, making a guess....

So if you want some unqualified logic, follow me...

1) That part is possibly a spacer/adapter?

2) Not sure why a spacer is used in this application... either way, it deserves some form of seal or sealant...

3) If it is leaking, the seal or sealant has failed...

4) For an interesting picture of a Woodward Governor, Ross posted one earlier... for an F

5) That discussion is for a Bravo That is still looking to identify what part of the gov is leaking...

6) try to find some pics looking at the bottom to see if the spacer is bolted on separately from the mounting bolts... this will give you a hint if the spacer could have come loose. Chances are (if it is only a spacer) the spacer may just have bolt holes in line with the mounting bolts....

7) If you have more time, less money... work on new seals...

8) If you have more money, less time... go for the one time fix, go PRU...

9) Great pic of the ground strap! 

10) from a pic of an eco-Airedale’s device I found, looking up from the bottom... there are four screws that hold the bottom plate to the bottom of the main casting....

When you get together with your mechanic.... Share your pics and this pic too to help define your next steps.... could be some seals and screws that need to be cleaned and torqued...

maybe great logic... but still completely un-qualified as a mechanic...

 

Best regards,

-a-

[N201MKTurbo]

That is the parting line for the governor oil pump. There can be up to 400 PSI there. It won’t hurt anything, it will just make a mess.

I once asked a prop shop about getting a new seal and was told they don’t make that seal any more and you have to take a seal that is too big, cut a bit out of it and butt splice the ends together. I don’t know if that is still true or ever was, the splice could have failed.

it Is a square section o-ring, so torquing the bolts won’t change anything. The two halves of the oil pump are already clamped together.

[carusoam]

I have seen gear pumps precision built out of plates of steal.... (plastics industry)

One piece housed the gears, the top and bottom plates held the flow channels for oil entering and exiting the pump...

The seals were precision milled steel... a very high temperature solution... not applicable here...

 

Onto the topic of building a seal... MS has a guy who deals in high temperature silicone rubber... that may be able to build square o-rings UV cured to the right dimensions.... or cut into any shape needed...

PP thinking out loud, only....

Best regards,

-a-

[Yetti]

I am thinking that the seal is a dried and started dripping. I think you gain useful lbs by going to the newer governor.  Probably could fly it till it becomes a bad leak.    Also thinking that the person who installed the white ground wire did it wrong by having the ring connector under a split ring lock washer.   It caused the wire to twist when the bolt was tightened.   It has also twisted the ring connector and weakened it, given enough vibration it will break.    The proper way would have been to put a flat washer between the ring connector and spit washer.   You get plus points for the brown oil/fuel hose lines.

 

 

Edited January 7, 2019 by Yetti

[Vance Harral]

Thanks for the replies so far.  We've decided to R&R the governor for either replacement or overhaul and are in the process of scheduling the work with our local shop.  A complicating factor is we have an ADS-B installation coming up in about two weeks that requires flying the airplane to the avionics shop, and we don't want to miss our slot.  The local consensus is it's not an excessive risk to live with the prop governor leak a few weeks until the ADS-B installation is complete, so that's probably the direction we're headed.

We got a recommendation from LASAR on prop governor overhaul: Truespeed Aero Governors.  They work on older governors, approximately $600 to overhaul if the core is good.  If it's not, they have a couple of options for replacement.  We're hopeful an overhaul will work out, as in our opinion, the PCU5000 cost is too large and the weight improvement too small to be attractive. 

[N201MKTurbo]

57 minutes ago, Vance Harral said:

Thanks for the replies so far.  We've decided to R&R the governor for either replacement or overhaul and are in the process of scheduling the work with our local shop.  A complicating factor is we have an ADS-B installation coming up in about two weeks that requires flying the airplane to the avionics shop, and we don't want to miss our slot.  The local consensus is it's not an excessive risk to live with the prop governor leak a few weeks until the ADS-B installation is complete, so that's probably the direction we're headed.

We got a recommendation from LASAR on prop governor overhaul: Truespeed Aero Governors.  They work on older governors, approximately $600 to overhaul if the core is good.  If it's not, they have a couple of options for replacement.  We're hopeful an overhaul will work out, as in our opinion, the PCU5000 cost is too large and the weight improvement too small to be attractive. 

$600 for a governor overhaul is a good deal. You might ask if they will just replace the seal, it would be less than $100. I have found that most prop shops won't do an IRAN anymore, but it doesn't hurt to ask.

I would let it ride until your avionics work is done. Like I said before. It will most likely happily leak for the next 10 years without causing you any other issues.

[Vance Harral]

5 minutes ago, N201MKTurbo said:

You might ask if they will just replace the seal.

Not a bad idea, we might give that a try.

I appreciate the reassurance about letting it ride a few weeks.  Don't want to do that for very long, though, as the volume of oil it's leaking is bad enough to easily mask other problems should they occur.  Our goal isn't "bone dry", just "dry enough to be able to detect a change".  We'll likely have the shop address a couple of other issues while waiting on the prop governor, e.g. the rubber couplings on the drain-back lines from the rocker compartments are seeping, oil sump gasket is oozing a bit (may or may not have some luck torquing the bolts there), etc.

This engine is right at 2000 hours (and 27 years) since overhaul, so it really doesn't owe us anything.  But compressions, oil analysis, and borescope all look good, and we feel like a few small oil seeps here and there aren't reason enough to pull the trigger on a full overhaul - even at the 2000 hour point.  However, that strategy is only reasonable if you keep track of where the oil is actually leaking from, and ensure it's not something like a crack in the case.