Push Rod Seals

[T. Peterson]

I have a 1979 231 K TSIO 360. I bought the airplane a year ago and was told a couple of the push rod seals were leaking, but not a big deal. After a few weeks of oil dripping on my tire a different shop confirmed that it was indeed push rod seals, so I had them all replaced, but the leaking never stopped. So at annual I had it checked again and that shop felt it was coming from some sort of engine mount (?) . Whatever it was they changed it. If I was home I would check the logbook to see exactly what they did. I don’t think it’s relevant as the source of the leak is as described below. At any rate the leaking never stopped. 
Yesterday I took it to a 4th shop and we are back to push rod seals again. The tech showed me where they were leaking after a thorough cleaning and run up. Two on the left side were the worst, but all or most were leaking some. There is also some question as to the front left cylinder leaking at the base. 
So a seal kit is going to be ordered and these seals replaced again.

A friend of mine told me about a company “Real Gasket” that supposedly makes superior push rod seals.

Do any of you have any experience with these seals?

Have any of you wrestled with this same problem?

Do you have any words of wisdom?

The engine was installed new in 1991. It has 1300 hours on it.

Thanks,

Torrey

[Vance Harral]

Our Lycoming IO-360-A1A engine was last overhauled about the same time as yours - over 30 years ago.  Currently at about 2400 hours since last overhaul.  Different engine, but basically the same pushrod and seal geometry.

We purchased the airplane in 2004 and two of the 8 pushrod seals have basically always dribbled a little oil in the ensuing 19 years.  It runs down through the cylinder fins and shows up lower in the engine compartment.  We've replaced the seals multiple times in an attempt get the dribbling to stop, trying both the original rubber gaskets, and some newer, fancy fluorosilicone seals.  It helped, but we never got things completely dry.  I finally decided to just stop worrying about it.

In speaking with a number of owners like you and I, who choose to operate engines for decades since the last overhaul, I have yet to find a single such owner with a "dry" engine.  They all have some degree of minor oil leaks, which the owners choose to tolerate.  I'm convinced such leaks from pushrod seals, drainback tubes, the oil pan, and even in some cases around the case halves is simply not a serious risk.  It can, however, mask a new leak from somewhere else that is a larger concern.  That's the only thing that gives me pause about it.

[T. Peterson]

2 hours ago, Vance Harral said:

Our Lycoming IO-360-A1A engine was last overhauled about the same time as yours - over 30 years ago.  Currently at about 2400 hours since last overhaul.  Different engine, but basically the same pushrod and seal geometry.

We purchased the airplane in 2004 and two of the 8 pushrod seals have basically always dribbled a little oil in the ensuing 19 years.  It runs down through the cylinder fins and shows up lower in the engine compartment.  We've replaced the seals multiple times in an attempt get the dribbling to stop, trying both the original rubber gaskets, and some newer, fancy fluorosilicone seals.  It helped, but we never got things completely dry.  I finally decided to just stop worrying about it.

In speaking with a number of owners like you and I, who choose to operate engines for decades since the last overhaul, I have yet to find a single such owner with a "dry" engine.  They all have some degree of minor oil leaks, which the owners choose to tolerate.  I'm convinced such leaks from pushrod seals, drainback tubes, the oil pan, and even in some cases around the case halves is simply not a serious risk.  It can, however, mask a new leak from somewhere else that is a larger concern.  That's the only thing that gives me pause about it.

Thank you so much for the insight! I will give it one more try and then quit worrying about it!

[231MJ]

I have run both the Lycoming IO-360 and the Continental TSIO-360 and the Lycoming leaks a lot less than the Continental, in my experience.  I seem to be replacing the seals on my Continental about every 4 years and this year I did use the "Real Gasket" seals.  The Real Gasket system is engineered a little differently and I'm hoping it stays dry for a longer period of time.  My IA says it's gonna leak at some point and just get used to it...Replacing the seals is kinda involved so suggest doing it only if you can't live with the leaking.

[N201MKTurbo]

I put the Real Gasket pushrod tubes on my Cessna. One of them leaks... Just a little. I'd say about two drips an hour.

[M20F-1968]

Be sure to re-torque them after putting the Real Gasket seals on, per their specs.

John Breda

[1980Mooney]

16 minutes ago, 231MJ said:

I have run both the Lycoming IO-360 and the Continental TSIO-360 and the Lycoming leaks a lot less than the Continental, in my experience.  I seem to be replacing the seals on my Continental about every 4 years and this year I did use the "Real Gasket" seals.  The Real Gasket system is engineered a little differently and I'm hoping it stays dry for a longer period of time.  My IA says it's gonna leak at some point and just get used to it...Replacing the seals is kinda involved so suggest doing it only if you can't live with the leaking.

That's interesting.  The Lycoming IO-360 in my 1980 J was rather leak prone.  I can't recall the specifics now but it seemed like we were always chasing a leak .  However after my Missile conversion to a Continental IO-550 I have not experienced any leaks in 22 years.  It has been tight.  The only time I see oil is if I overfill the oil fill pipe by pouring too fast or carelessly.  Perhaps the Continental IO-360 is more trouble prone.

[N201MKTurbo]

2 minutes ago, M20F-1968 said:

Be sure to re-torque them after putting the Real Gasket seals on, per their specs.

John Breda

The pushrod tubes on both the Continental and Lycoming are spring loaded. What are you torquing? Are you thinking about valve cover gaskets?

 

[M20F-1968]

Just now, N201MKTurbo said:

The pushrod tubes on both the Continental and Lycoming are spring loaded. What are you torquing? Are you thinking about valve cover gaskets?

 

Sorry, thinking about valve cover gaskets.

John Breda

[Guest]

5 hours ago, T. Peterson said:

I have a 1979 231 K TSIO 360. I bought the airplane a year ago and was told a couple of the push rod seals were leaking, but not a big deal. After a few weeks of oil dripping on my tire a different shop confirmed that it was indeed push rod seals, so I had them all replaced, but the leaking never stopped. So at annual I had it checked again and that shop felt it was coming from some sort of engine mount (?) . Whatever it was they changed it. If I was home I would check the logbook to see exactly what they did. I don’t think it’s relevant as the source of the leak is as described below. At any rate the leaking never stopped. 
Yesterday I took it to a 4th shop and we are back to push rod seals again. The tech showed me where they were leaking after a thorough cleaning and run up. Two on the left side were the worst, but all or most were leaking some. There is also some question as to the front left cylinder leaking at the base. 
So a seal kit is going to be ordered and these seals replaced again.

A friend of mine told me about a company “Real Gasket” that supposedly makes superior push rod seals.

Do any of you have any experience with these seals?

Have any of you wrestled with this same problem?

Do you have any words of wisdom?

The engine was installed new in 1991. It has 1300 hours on it.

Thanks,

Torrey

High internal crankcase pressures (blow by) can cause leaks at push rod tubes.

[T. Peterson]

37 minutes ago, M20Doc said:

High internal crankcase pressures (blow by) can cause leaks at push rod tubes.

Hmmm….interesting. I assume blow by is the result of cylinder compression getting past the valves or the rings?

So I will bring this to the mechanics attention. No point in wasting money on new seals if blow by is the culprit. Engine was borescoped at prebuy. In my very uneducated understanding of mechanical things, it seems leaking valves should have been seen?…..and then confirmed with a compression test? In my further limited understanding I assume I may be facing a top overhaul? 
What is the typical cost of a top overhaul on a 6 cylinder engine?

Thank you so much for weighing in!

[T. Peterson]

1 minute ago, T. Peterson said:

Hmmm….interesting. I assume blow by is the result of cylinder compression getting past the valves or the rings?

So I will bring this to the mechanics attention. No point in wasting money on new seals if blow by is the culprit. Engine was borescoped at prebuy. In my very uneducated understanding of mechanical things, it seems leaking valves should have been seen?…..and then confirmed with a compression test? In my further limited understanding I assume I may be facing a top overhaul? 
What is the typical cost of a top overhaul on a 6 cylinder engine?

Thank you so much for weighing in!

One more question: My oil pressure is on the low side, just to the right of the yellow, and oil temperature is well right of center though solidly in the green. Is this also a sign of blow by?

Thanks,

Torrey

[T. Peterson]

2 hours ago, M20F-1968 said:

Be sure to re-torque them after putting the Real Gasket seals on, per their specs.

John Breda

I won’t be re-torquing squat, but I will mention it to the tech!

[carusoam]

If changing the seals didn’t work…

The environment these seals live in may be pretty crusty… or easily scratched when pulling the old seals out

From ultra hot, to kinda steamy, to huge temp changes….

It may be possible that cleaning the sealing surfaces may be a good idea…

How hard is it to pull the tube out for a decent cleaning and inspection?

What do the tubes cost new, on the open market?

 

PP speculation only… I haven’t had this leak before…

Best regards,

-a-

[MikeOH]

It would seem to me (NOT an A&P!) that pulling the tubes 'for a decent cleaning and inspection' is going to be the same amount of work as to change the seal: pushrod needs to be removed in order to remove the tube, removing the push rod is going to require removing the rocker arm, removing the rocker arm is going to require removing the valve covers...UGH!

If I was faced with a leaking tube seal I'd see if I could talk my A&P into trying the following nutso idea:  push back the springs and tube to cut out the seals on each end of the tube.  Take a brand spanking new seal, slide it over a suitable diameter metal rod/tube/whatever and very carefully cut it with a brand new razor blade!  Now, you have a 'split-ring' seal you can install without any other disassembly.  Orient so the cut is at 12 o'clock with a little Permatex on the split when you install.

Worst case, you're back where you started

[T. Peterson]

11 minutes ago, MikeOH said:

It would seem to me (NOT an A&P!) that pulling the tubes 'for a decent cleaning and inspection' is going to be the same amount of work as to change the seal: pushrod needs to be removed in order to remove the tube, removing the push rod is going to require removing the rocker arm, removing the rocker arm is going to require removing the valve covers...UGH!

If I was faced with a leaking tube seal I'd see if I could talk my A&P into trying the following nutso idea:  push back the springs and tube to cut out the seals on each end of the tube.  Take a brand spanking new seal, slide it over a suitable diameter metal rod/tube/whatever and very carefully cut it with a brand new razor blade!  Now, you have a 'split-ring' seal you can install without any other disassembly.  Orient so the cut is at 12 o'clock with a little Permatex on the split when you install.

Worst case, you're back where you started

Due to what Clarence said about blow-by I am thinking he may be on to something. If just one new seal was leaking I would think it was either a bad seal or damaged in installation. But all of them…..

As far as your installation shortcut, I would try that on the two worse ones if I was doing the work. I don’t think the mechanic is going to agree to it….

[T. Peterson]

36 minutes ago, carusoam said:

If changing the seals didn’t work…

The environment these seals live in may be pretty crusty… or easily scratched when pulling the old seals out

From ultra hot, to kinda steamy, to huge temp changes….

It may be possible that cleaning the sealing surfaces may be a good idea…

How hard is it to pull the tube out for a decent cleaning and inspection?

What do the tubes cost new, on the open market?

 

PP speculation only… I haven’t had this leak before…

Best regards,

-a-

Those are all good suggestions which I will bring up to the mechanic. Thank you!

[N201MKTurbo]

23 minutes ago, MikeOH said:

It would seem to me (NOT an A&P!) that pulling the tubes 'for a decent cleaning and inspection' is going to be the same amount of work as to change the seal: pushrod needs to be removed in order to remove the tube, removing the push rod is going to require removing the rocker arm, removing the rocker arm is going to require removing the valve covers...UGH!

If I was faced with a leaking tube seal I'd see if I could talk my A&P into trying the following nutso idea:  push back the springs and tube to cut out the seals on each end of the tube.  Take a brand spanking new seal, slide it over a suitable diameter metal rod/tube/whatever and very carefully cut it with a brand new razor blade!  Now, you have a 'split-ring' seal you can install without any other disassembly.  Orient so the cut is at 12 o'clock with a little Permatex on the split when you install.

Worst case, you're back where you started

Getting the rocker arms off isn’t so bad, especially if you have a good spring compressor. I made one from a wrecking bar (very hard steel) that uses one of the valve cover screw holes. It takes about 30 seconds to get the rocker off. 
 

Getting the pushrod tubes off is way harder than the rocker. This is all about the Lycoming BTW. I have the pushrod tube spring compressor for the Continental, but I have way more experience with Lycomings. I would need to make a new compressor for the Continental. There are two kinds of valve spring compressors, one for getting the rockers out and one for getting the keepers out after you have the rocker out. The latter can use the rocker shaft as a pivot, the former cannot.

[Will.iam]

Hey torrey i thought my push rods were leaking but come to find out it was the rocker cover gaskets as they were the original cork gaskets. I ordered and installed the silicone gasket versions and my oil leaking stopped. As far as blowby check your engine oil color after an oil change. The worse the blowby the quicker the oil turns black. I have blowby as my oil turns black by 5 hours. Where as guys that have no blowby their oil is only slightly less golden by oil change at 25 hours! Also realize the higher your oil temperature gets the lower the oil pressure goes. On takeoff on cold mornings, my oil pressure will be close to 80 psi but if i do a takeoff after the engine has been running like say a fuel stop and the oil is still hot then my takeoff oil pressure is closer to 60 psi. In other words if your oil temp is unusually high i would investigate that first as you may have an issue with your oil cooler not getting enough cooling air or a restriction in the the cooler that if you fix that would bring your oil temp down which would bring your oil pressure up. 

Edited March 12, 2023 by Will.iam
Additional info

[T. Peterson]

5 minutes ago, Will.iam said:

Hey torrey i thought my push rods were leaking but come to find out it was the rocker cover gaskets as they were the original cork gaskets. I ordered and installed the silicone gasket versions and my oil leaking stopped. As far as blowby check your engine oil color after an oil change. The worse the blowby the quicker the oil turns black. I have blowby as my oil turns black by 5 hours. Where as guys that have no blowby their oil is only slightly less golden by oil change at 25 hours! 

Thanks Will. Excellent point! I was not aware of that indicator. I will watch watch my oil closely but I am pretty sure it will darken quickly. I am going to cancel the seal replacement. I am sure it will cost north of a thousand bucks, and I have little confidence it will accomplish anything. I’m not going to just throw that money away. I am going to call the shop Monday morning and cancel. Too many unknowns at this juncture. I despise that oil leaking all over my front tire, but am pretty sure a top overhaul or new engine is the only solution. So I will keep covering the tire with a rag until that time comes.

I appreciate you and all the fellas that chimed in on this issue. You all just saved me a ton of money on a useless seal change.

[Will.iam]

15 minutes ago, T. Peterson said:

Thanks Will. Excellent point! I was not aware of that indicator. I will watch watch my oil closely but I am pretty sure it will darken quickly. I am going to cancel the seal replacement. I am sure it will cost north of a thousand bucks, and I have little confidence it will accomplish anything. I’m not going to just throw that money away. I am going to call the shop Monday morning and cancel. Too many unknowns at this juncture. I despise that oil leaking all over my front tire, but am pretty sure a top overhaul or new engine is the only solution. So I will keep covering the tire with a rag until that time comes.

I appreciate you and all the fellas that chimed in on this issue. You all just saved me a ton of money on a useless seal change.

To give you a reference those silicone gaskets were $6 a pop so $72 for 12 and i replaced the star washers which took 48 and a bag of 50 i think was $15 so for less that $100 in parts, so the majority of your expense would be labor only and that was in cleaning the old cork gasket that had “welded” to the cylinder side from heat to remove.  It was a 3 hour ordeal. 

[Shadrach]

18 hours ago, MikeOH said:

It would seem to me (NOT an A&P!) that pulling the tubes 'for a decent cleaning and inspection' is going to be the same amount of work as to change the seal: pushrod needs to be removed in order to remove the tube, removing the push rod is going to require removing the rocker arm, removing the rocker arm is going to require removing the valve covers...UGH!

If I was faced with a leaking tube seal I'd see if I could talk my A&P into trying the following nutso idea:  push back the springs and tube to cut out the seals on each end of the tube.  Take a brand spanking new seal, slide it over a suitable diameter metal rod/tube/whatever and very carefully cut it with a brand new razor blade!  Now, you have a 'split-ring' seal you can install without any other disassembly.  Orient so the cut is at 12 o'clock with a little Permatex on the split when you install.

Worst case, you're back where you started

Removing rocker box covers, arms and push rods is not that time intensive. As in maybe half an hour or so to remove from all four cylinders. Dicking around trying to get a split seal  oriented, seated properly and glued is not worth it.

[T. Peterson]

16 minutes ago, Shadrach said:

Removing rocker box covers, arms and push rods is not that time intensive. As in maybe half an hour to remove all four. Dicking around trying to get a split oriented, seated properly and glued is not worth it.

I don’t do my own work anyway, so it’s a moot point.

But since you have been kind enough to comment, what do you think about the blow-by theory posted by Clarence. I am no engineer or mechanic, but what he said makes sense to me, especially in light of the fact that the seals are all less than a year old and the leaking never stopped. The fellow that replaced the seals may have damaged one during installation, but not all. At least I think it not plausible that all would be damaged or incorrectly installed.

At any rate I will do nothing till I get my bearings on which direction to proceed. Right now I have no inclination except to wait.

[Guest]

This might help, from the IPC.  Not sure which model you own, but they’re all generally the same.  No special tools required to remove anything, even a pushrod spring compressor isn’t really needed if you’re crafty.

Crankcase pressure check is done with an old airspeed indicator or a water manometer and an old oil cap with a hose to connect them together.  Check the Continental M-O manaul, but from memory, 16” of water or 90mph is the limit.

Blowby will cause oil to collect on the bottoms of the spring coils.

[Shadrach]

15 hours ago, T. Peterson said:

I don’t do my own work anyway, so it’s a moot point.

But since you have been kind enough to comment, what do you think about the blow-by theory posted by Clarence. I am no engineer or mechanic, but what he said makes sense to me, especially in light of the fact that the seals are all less than a year old and the leaking never stopped. The fellow that replaced the seals may have damaged one during installation, but not all. At least I think it not plausible that all would be damaged or incorrectly installed.

At any rate I will do nothing till I get my bearings on which direction to proceed. Right now I have no inclination except to wait.

Offering a critique of Clearance’s maintenance opinions is well above my pay grade. I don’t think he was diagnosing your specific engine so much as offering a known cause of recurring leaks. Does your engine exhibit any other symptoms of excessive case pressure?   SB M89-9  covers how to test crankcase pressure with a manometer or an old airspeed indicator.  The maximum acceptable reading for your engine at full power is 4.00” H2O or 90MPH indicated.

Several of my pushrod seals are weeping as well, but their sub optimal condition be can verified visibly. They’ll be replaced at annual in October.