Need advice

[Dream to fly]

I am looking for some advice as to what to do in regards to an oil leak that has been since day one of my ownership of this plane.  As I have posted about all the horrors of this plane I have finally been able to fly it and after all the work it flies pretty well.  I am actually impressed how well and graceful it flies.  However I have had oil leaks that are really making a mess. It all seams to be coming from the back of the engine.  I just can't see from what. I already resealed the magnetos and the prop governor was overhauled when I bought the plane.  I think it could be the accessory drive case or the fuel pump but I am throwing a dart on that.  So I was thinking about buying another engine and building it.  Then swapping it in.  I also at that point was thinking what would it take to finally convert this thing into a J model since I think all the speed mods are done but the cowl.  Just weighing options since this has become the money pit and I'll own it till I stop flying.   My thinking was to peak it out on performance and speed.  

[Yetti]

fuel pump gasket is a good choice.   The other trouble spot is the valve drain lines where they connect with a rubber hose to the engine....   I am always tightening the clamps.   And I replaced all the hose.

[TheAv8r]

There are a number of different places that are common causes of oil leaks in Mooney (Google searching Mooney oil leak will come up with similar threads) but I'd suggest not buying a new engine to fix an oil leak. That's like burning your house down because there's spiders in the bathroom. Sure, it will solve the problem, but there are way easier, less expensive ways to do it, unless your engine is already very high time and you're facing an OH soon regardless (and even then, new engines can have oil leaks too). 

What's your current oil consumption?

The best way to trace an oil leak is to thoroughly clean the engine, then run it and trace the oil flow. If your oil consumption is reasonable, not getting worse, and all other indications (oil filter, cylinder compression, borescope etc.) are healthy, then there's no reason to buy a new engine and swap it out.

[David Lloyd]

At the rear of the engine are fuel pump gasket, oil filter, all connections, vac pump gasket, prop governor & gasket, oil return lines.  Torn magneto gaskets are something I have seen a couple times.  It's a pain to check each of these but a lot easier than installing a new engine.

[philip_g]

we had to proseal the entire engine case seam to stop a leak. turned out the oil pressure gauge was reading low so oil pressure was WAY higher than expected, probably adding to our woes

[Dream to fly]

Ok during the last annual the engine was retimed.  I honestly can't see the stain where the oil is coming from.  If the logbooks are correct the oil pump was replaced prior to my purchase as was the gears and the prop governor.  I replaced both mags 200 hrs ago and the leak was there before I did that.  it hasn't changed in volume, but it is very noticeable, and it is making a mess.  Is it allowed to put and engine oil dye in the oil to see if ultraviolet light can pinpoint it?

[Prior owner]

Replacing the oil pump gears while the engine is in the plane will usually require that the portion of the sump gasket that is under the accessory case is cut away and a new section of gasket is put in there (unless the entire sump is removed). You can get leaks at the two bottom corners where the accessory case cover, the back of the engine case, and the sump all meet. A good practice is to dab pro seal  in Those two corners just before re-installing the accessory case cover. Sometimes people use silicone. Sometimes nothing at all…. It could be your culprit. If so, you may want to super clean the corners and dab pro-seal over them to try to seal it.
 

Oil dipstick tube bottom gasket can also leak and drool towards the rear of the engine. The tach drive can leak (not very common). If the mags were re-timed at annual without pulling them and replacing the gaskets, that might be your issue. 

Good luck…chasing engine oil leaks is not much fun. Cleaning the entire engine until it is bone dry is the first step.

[Vance Harral]

Cleaning the engine to bone dry is indeed the first step.  Once that's done, I've had good luck with UV leak detection dye, e.g. https://www.amazon.com/Interdynamics-Certified-Fuel-Systems-Ounce/dp/B002M4G24U, a trick explained to me by a long-certified A&P mechanic.  Get everything bone dry, pour a bottle of the dye into the oil fill tube (don't spill it outside the engine!), run the engine at high power for a short period of time on the ground, de-cowl, and use a cheap UV flashlight in a dark hangar to look for the source of leaks.

I know of no specific regulatory prohibition on doing this, but I make no claim that it's legal/approved/etc.  The most conservative approach is to do this coincident with an oil change.  Add the dye right before the change, ground run the engine (to warm it up for the oil change, natch), identify your leaks, then drain the oil-with-dye as part of a normal oil change before you fly again.  There is no particular reason to fly with dye in the oil anyway, as airflow through the cowl at speed just tends to blow leaking oil away from the original source of the leak anyway.

For what it's worth, we did this after the conventional steps of replacing the rocker cover gaskets, tightening up the couplings on the cylinder head drain-back tubes, etc.  What we found was a small leak at one of the pushrod tube seals that we had fixed, and a series of small leaks around the oil pan gasket, which we have chosen to live with in the short term (dropping the oil pan to install a new gasket is somewhat major surgery).

[Dream to fly]

I use the dye in diesels all the time and a dark shop is amazing at what you see.  Sometimes it is scary!   My gut keeps thinking the mags or the fuel pump are leaking but as @PilotCoyote said the tach drive could leak.  As stupid as this sounds it could be that easy because it is open to the air.  I have no tach cable and there is no cap on it I am almost positive of that.  I honestly have been looking from the sides and up.  

[Browncbr1]

Don’t forget oil pressure relief valve gasket.  

[Dream to fly]

5 hours ago, jacenbourne said:

There are a number of different places that are common causes of oil leaks in Mooney (Google searching Mooney oil leak will come up with similar threads) but I'd suggest not buying a new engine to fix an oil leak. That's like burning your house down because there's spiders in the bathroom. Sure, it will solve the problem, but there are way easier, less expensive ways to do it, unless your engine is already very high time and you're facing an OH soon regardless (and even then, new engines can have oil leaks too). 

What's your current oil consumption?

The best way to trace an oil leak is to thoroughly clean the engine, then run it and trace the oil flow. If your oil consumption is reasonable, not getting worse, and all other indications (oil filter, cylinder compression, borescope etc.) are healthy, then there's no reason to buy a new engine and swap it out.

My thinking was if I had to fix the gasket between the accessory case I rather just have an engine to drop in.  This engine is mid time and it runs great consumption is probably a qt plus every 8 hrs.  But I think I am losing more than I am burning its coating the belly pretty good.  Selling this to offset a rebuilt would be an option and less down time.  Dollars wise its a reach but this whole project has been crazy so I might as well go all in.  I am going to run it for 10 more hours and then steam clean it and run it on dye and see  what is leaking.  My goal is to use this engine for another year or two and then swap it out if I can get the oil leak under control.  The mirror trick has been little help so I am having Snap-On drop off a borescope with a wide angle lens and I'll see if that helps.  

[Ragsf15e]

21 minutes ago, Dream to fly said:

My thinking was if I had to fix the gasket between the accessory case I rather just have an engine to drop in.  This engine is mid time and it runs great consumption is probably a qt plus every 8 hrs.  But I think I am losing more than I am burning its coating the belly pretty good.  Selling this to offset a rebuilt would be an option and less down time.  Dollars wise its a reach but this whole project has been crazy so I might as well go all in.  I am going to run it for 10 more hours and then steam clean it and run it on dye and see  what is leaking.  My goal is to use this engine for another year or two and then swap it out if I can get the oil leak under control.  The mirror trick has been little help so I am having Snap-On drop off a borescope with a wide angle lens and I'll see if that helps.  

A tiny leak will make the belly very oily.  Additionally, these engines all lose some through the breather which goes directly on the belly.  It can be a small leak and look like a huge mess under there.  I’d definitely try to clean it up somewhat and/or live with it because you’re gonna spend a whole lot of time and money but there’s likely nothing really “wrong” with the engine.

[Dream to fly]

7 minutes ago, Ragsf15e said:

A tiny leak will make the belly very oily.  Additionally, these engines all lose some through the breather which goes directly on the belly.  It can be a small leak and look like a huge mess under there.  I’d definitely try to clean it up somewhat and/or live with it because you’re gonna spend a whole lot of time and money but there’s likely nothing really “wrong” with the engine.

My fear is It is covering my exhaust shield.  The exhaust system is 25hrs old and was installed brand new.  The shield is covered in oil drippings and it looks like it went thru the war.  I am sure if it keeps collecting and I don't scrub the burnt oil off, it will at some point catch fire.   I don't mind the little drips here and there but this after a two hour flight will leave a beer can size puddle after sitting 36-48hrs under the back side of the front tire.  Ultimately the new pucks I put in are probably going to need replacement from being oil soaked so I think it needs to be addressed sooner than later.  The good news is this plane is applying a really good corrosion protection and my front landing gear will probably never need grease:)

[Ragsf15e]

2 hours ago, Dream to fly said:

My fear is It is covering my exhaust shield.  The exhaust system is 25hrs old and was installed brand new.  The shield is covered in oil drippings and it looks like it went thru the war.  I am sure if it keeps collecting and I don't scrub the burnt oil off, it will at some point catch fire.   I don't mind the little drips here and there but this after a two hour flight will leave a beer can size puddle after sitting 36-48hrs under the back side of the front tire.  Ultimately the new pucks I put in are probably going to need replacement from being oil soaked so I think it needs to be addressed sooner than later.  The good news is this plane is applying a really good corrosion protection and my front landing gear will probably never need grease:)

Yeah there might be something around there the oil isn’t good for, but mostly it’s just ugly looking corrosion protection.  

[vik]

On 12/8/2021 at 12:23 PM, PilotCoyote said:

Replacing the oil pump gears while the engine is in the plane will usually require that the portion of the sump gasket that is under the accessory case is cut away and a new section of gasket is put in there (unless the entire sump is removed). You can get leaks at the two bottom corners where the accessory case cover, the back of the engine case, and the sump all meet. A good practice is to dab pro seal  in Those two corners just before re-installing the accessory case cover. Sometimes people use silicone. Sometimes nothing at all…. It could be your culprit. If so, you may want to super clean the corners and dab pro-seal over them to try to seal it.
 

Oil dipstick tube bottom gasket can also leak and drool towards the rear of the engine. The tach drive can leak (not very common). If the mags were re-timed at annual without pulling them and replacing the gaskets, that might be your issue. 

Good luck…chasing engine oil leaks is not much fun. Cleaning the entire engine until it is bone dry is the first step.

Looks like my problem. The oil is leaking from the accessory case and oil sump gasket joint. Some work was done on the accessory case, so the rear portion of the sump gasket was replaced. Should I pull the oil sump to replace the whole gasket. If I do that, what sealant (if any) should I use on the joint?

 

[N201MKTurbo]

1 hour ago, vik said:

Looks like my problem. The oil is leaking from the accessory case and oil sump gasket joint. Some work was done on the accessory case, so the rear portion of the sump gasket was replaced. Should I pull the oil sump to replace the whole gasket. If I do that, what sealant (if any) should I use on the joint?

 

I've always used Permatex and it hasn't leaked. Polysulphide  (Pro Seal) should work well too. I never any use sealant on aircraft gaskets, except at that joint. It also helps to carefully install the accessory cover so you don't squirrel the gaskets around and screw up the sealant joint.

[markgrue]

Not sure what oil you use but I do know Aeroshell 15-50 has a  dye in it that glows under ultraviolet light.

 

Mark

[Skates97]

On 12/8/2021 at 8:50 AM, Yetti said:

fuel pump gasket is a good choice.   The other trouble spot is the valve drain lines where they connect with a rubber hose to the engine....   I am always tightening the clamps.   And I replaced all the hose.

And it seems every now and then a clamp will fail. After many hours of leak free flying I've been trying to find one. It's just tiny but makes a mess inside the cowl. On my last oil change I found a drip hanging from the oil return line from the #1 cylinder. Went to tighten the clamp and it was stripped. Replaced the clamp and all is well again.

On 12/8/2021 at 2:56 PM, Vance Harral said:

Cleaning the engine to bone dry is indeed the first step.  Once that's done, I've had good luck with UV leak detection dye, e.g. https://www.amazon.com/Interdynamics-Certified-Fuel-Systems-Ounce/dp/B002M4G24U, a trick explained to me by a long-certified A&P mechanic.  Get everything bone dry, pour a bottle of the dye into the oil fill tube (don't spill it outside the engine!), run the engine at high power for a short period of time on the ground, de-cowl, and use a cheap UV flashlight in a dark hangar to look for the source of leaks.

I know of no specific regulatory prohibition on doing this, but I make no claim that it's legal/approved/etc.  The most conservative approach is to do this coincident with an oil change.  Add the dye right before the change, ground run the engine (to warm it up for the oil change, natch), identify your leaks, then drain the oil-with-dye as part of a normal oil change before you fly again.  There is no particular reason to fly with dye in the oil anyway, as airflow through the cowl at speed just tends to blow leaking oil away from the original source of the leak anyway.

For what it's worth, we did this after the conventional steps of replacing the rocker cover gaskets, tightening up the couplings on the cylinder head drain-back tubes, etc.  What we found was a small leak at one of the pushrod tube seals that we had fixed, and a series of small leaks around the oil pan gasket, which we have chosen to live with in the short term (dropping the oil pan to install a new gasket is somewhat major surgery).

This is the best way I know of to find a leak. We did this but instead of just a ground run flew it around the pattern once. Yes, it can blow around inside, but one trip around the pattern doesn't blow it around much and with a black light you should be able to see where the leak is coming from. It is often not anywhere near where you think it is.

[vik]

On 12/13/2021 at 10:00 AM, N201MKTurbo said:

I've always used Permatex and it hasn't leaked. Polysulphide  (Pro Seal) should work well too. I never any use sealant on aircraft gaskets, except at that joint. It also helps to carefully install the accessory cover so you don't squirrel the gaskets around and screw up the sealant joint.

Pardon my incompetence, but Permatex makes so many different products. Same is with Pro Seal. I checked and many contain polysulphide. Which would you recommend? It is probably common knowledge among the community, but I have no clue.

[vik]

On 12/13/2021 at 2:16 PM, markgrue said:

Not sure what oil you use but I do know Aeroshell 15-50 has a  dye in it that glows under ultraviolet light.

 

Mark

I have heard that in UV light any oil will have some fluorescence, so no dye is needed. I tried once in a dark hangar with cheap UV flashlight. I indeed saw some traces of the oil which I could not see in daylight. I do not remember which oil was used at that time. Probably a mix of different brands, so the test is not really scientific. Maybe worth a try as the efforts required are minimal. 

[carusoam]

Summary for Joe…

1) Relying on the dye that Is in the oil… is a different problem already…. It is already spread far and wide… too much to find the source…

2) Adding the specific dye for finding leaks, one trip around the pattern… is enough to show the source… don’t fly too long… once you flood the cowling in fluorescent oil dye… again, too hard to find the source…

3) foot powder spray, another mechanic’s tool for finding oil leaks… try this first…

4) +1 for cleaning the engine really well…

5) All oil leaks are easy to fix…. Except two…. Where there is no fixing for that…. Be on the look out for cracked cases, up by the cylinder mounts… and there is a tiny silk thread sealing the case halves together….

6) Stay open minded… each engine is unique… some have been known to be missing something from the last overhaul….that should have been there….  Don’t be surprised… 

7) The difficulty of finding the leak will be related to how much you really want a different engine…. If you start looking at new IO390s… the source of the leak will reveal itself easily….

8) If looking for the most efficient replacement of exactly what you have… the tiny oil leak source will be a micro scratch in a machined surface that is allowing a new seal to leak…. 

9) while looking at alternative engines… you can always consider getting things like pistons with 10:1 compression ratios… or a fancy electronic ignition, or roller cam followers….

 

Its really cool when you have so much engine experience already….  The challenging part is the tightness around the engine….

 

 

10) if you really want to spend a ton of money… the IO550 makes a great engine for the mid body Mooney….  Would need to write an STC very similar to a copy of the M20J Missile STC….  

Timing wise… it’s probably a good afternoon to clean and find the leak…

Going all in and building an M20F Missile would probably take a year….

Choose your weapon!

Best regards,

-a-

[Dream to fly]

@carusoam, Thanks!  My weapon of choice would be to burn this one and get a jet but I am invested so I like tinkering and I can't leave it alone. I might just build me an IO-390.  It could be fun.  The oil leak I have appears to be coming from the back accessory case.  I didn't add dye yet, but I did hit it with UV light and it seems to be streaming from the corners.  The other leak looks like where the Prop governor mates too the case.   I have to decide how much I want to deal with this engine.  It runs good and the numbers are fair on compression, however it has two mismatched cylinders and I didn't do the work so I am constantly thinking about it.  

[all4thekidz]

I believe one of the Studs to the Governor is a WET Stud and would require sealing.  If this is not done properly it will leak like a sieve!  This happened to ME!  

TODD

[Guest]

On 12/8/2021 at 7:12 PM, Dream to fly said:

My fear is It is covering my exhaust shield.  The exhaust system is 25hrs old and was installed brand new.  The shield is covered in oil drippings and it looks like it went thru the war.  I am sure if it keeps collecting and I don't scrub the burnt oil off, it will at some point catch fire.   I don't mind the little drips here and there but this after a two hour flight will leave a beer can size puddle after sitting 36-48hrs under the back side of the front tire.  Ultimately the new pucks I put in are probably going to need replacement from being oil soaked so I think it needs to be addressed sooner than later.  The good news is this plane is applying a really good corrosion protection and my front landing gear will probably never need grease:)

Easy off oven cleaner will remove the burnt oil from the muffler shroud.  Clean the engine really well, 100LL does a really good job of washing oil away leaving a dry surface.

Sources of pressurized oil on the back of your engine are the oil pressure fitting and hose, oil cooler transfer hoses, oil filter adapter, vacuum pump drive, propeller governor drive and tachometer drive shaft.  All of the rest are splash oil

Clarence

[EricJ]

I chased a leak that I absolutely could not find the source.    When my prop governor failed the shop I sent it to said it was leaking out the actuator shaft.    D'oh.   Never thought to look there.