Sticky Valve and intake valve cupping on IO360

[M20S Driver]

My good friend and a Mooney M20J old timer has an issue with his IO360 .  His engine was running rough due to low (zero) compression on one cylinder after take off from KSBP.   It appears that one of the  intake valves is cupped and not seating properly. Please see the pic.  A sticky intake valve is the primary suspect.

Has anyone seen this and has any idea what could cause it?   The mechanic pulled the cylinder today and will send it out for repair.   The main question is what could cause this other than a sticky valve?

[carusoam]

Got any JPI data he can share?

Lots of junk on the valve surface...

What did the other cylinder’s valves look like?

Good operating valves have the classic pizza look.

And it’s usually the hotter exhaust valves with the challenges...

If the valve has caused bad compression, the fuel isn’t burning as usual in that cylinder...

Seems as if it continuously was getting pulled out of the cylinder...?

Lets ask @M20Doc if he has seen intake valves damaged like that one...

PP thoughts only, not a mechanic

Best regards,

-a-

 

[Skyland]

Okay, just returned from a long drive working on my engine.  Here's the scenario.  My wife and I took the Mooney on a nice x-country trip from California to Maine, down the east coast and back again with a stop in Kerrville along the way for a factory tour (another story).  The plane performed flawlessly the entire time. 

One month later and about five more hours on the engine we were enroute on a one hour flight when a subtle vibration in the engine began, enough for me to sit up and take notice.  Lasted maybe 5-10 minutes then went away and landed uneventfully.  An hour later the startup, runup and takeoff were all normal - until about 600 feet when the vibration returned followed by a loss of rpms and power.  Circled the airport in a very slow climb while trying to troubleshoot.  Tried L, R and Both, mixture, prop cycling, throttle changes, switched tanks - no change.  All gauges in the green.  Vibration now getting quite bad like running on just three out of four cylinders.  Landed.

Removed top cowling, cylinder 1 was noticeably cooler than the others.  Pulled the injector and it was open and clean.  Pulled the prop through it was evident there was no compression in one cylinder.  Pulled number 1 spark plug to verify zero compression.  Wife went from a little concerned to a lot disappointed.  We missed our cruise departure in SD - but flew commercial to catch up with it in Cabo.  Wife back to near normal.

I had a mechanic look it over and verified the number 1 intake valve was stuck open.  Though at first it was a stuck lifter, removed it, bled out the oil, reassembled, and the valve still wouldn't close to get compression.  Removing the rotator cap on the valve stem allowed the valve to fully close and to attain hydraulic lifter clearance.  Did a runup and the engine ran normal.  Tried a test flight and got to 400 feet when the engine again began to run rough.  Ya, my bad.  

So pulled the cylinder today and it appears the number 1 intake valve is badly cupped.  Question is, how can an INTAKE valve get that hot by 400 feet?  BTW, this is an old school '79 J model, single probe EGT and CHT.  Engine analyser just appeared on xmas list.

Cylinder and valves to be inspected tomorrow so more to come...

[Guest]

My local engine guy calls that “tulipping” of the valve.  He says it’s due to large diameter, strong valve springs, heat and time.

Clarence

[Skyland]

Side note: I like the map depicting states flown to (landed in, I presume).  Couldn't find info on this site on "how to" so cobbled it together myself.  Didn't mean for it to be so big.  I'll try to fix that soon.  Can someone offer a procedure?

Back to my tuliped valve engine.  Sky Ranch Engineering Manual by John Schwaner may have nailed it.  On page 168, slightly paraphrasing, Pre-ignition causes slight engine roughness, extreme heating and pressure causing piston burning and intake valve stretching to the point where it no longer closes thus stopping the event.  Pre-ignition can be caused by magnito cross-fire.  Inspect distributor block for carbon tracking.  Both pre-ignition and detonation can cause extreme engine damage in a short period of time while all the engine instruments are "in the green".

This was written back in 1990.  Multi-cylinder engine analysers of today would no-doubt flag these events.  Okay, I'm sold.

A quick visual of the piston and cylinder when I removed them looked good so I'm hoping no damage beyond the valve.  I'll report back.

I'm also close to the 500 hour mag O/H so that should take care of the cross-fire possibility.  BTW, this is a 1200 hour factory reman with no log entries for previous cylinder work.

[carusoam]

Great follow-up...

+1 on getting an engine monitor...

Detonation/pre-ignition is difficult to know when it’s happening...

When a valve gets stuck open... look to see if there are any marks left between the valve and the piston contacting each other...

If you got heavy vibration... it may have been contact

 

I stuck an exhaust valve on an O360... bent the valve’s rod...

Having an engine monitor is nice... because when you lose a cylinder... you know there are three more still working...

If you see a cylinder go cold... you may not have enough power to go around to land... depending on how much weight you are carrying... and what else has failed in the engine...

When valves stick closed... is when things can get really weird... pressure stuck in the cylinder working against the other three that are trying to work.

Intake valves stuck open can start a fire in the intake system.... burning fuel in the intake can’t be good...

All that nice organized stuff involved with the four cycle engine can suddenly get disorganized by sticking a valve...

The tuliped valve is interesting... it got altered by hammering it for a while...

 

So... you might want to read up on cleaning valve guides... something called the ‘rope trick’ may be an informative read...

It would be smart to consider making sure the other three cylinders were not sharing what the first cylinder ate...

Exhaust valves are the ones that usually suffer from stickiness... they run extra hot in comparison... have a tendency to carbonized the oil in the valve guide... carbon blocks the flow of oil... no fresh oil... stuck valve!

No need to fly an engine with a valve that isn’t working right... full power, quickly heating the engine, things start to break or melt a few hundred feet above the ground....

Pre-ignition can be hot enough to melt a piston crown... in a few minutes....

Valves not seating properly may be a hot spot... valve seats are specifically places valves use to cool off... if they aren’t transferring heat away... all they need is to have an ember stuck on them to generate a source of ignition...

 

Check M20Doc’s input closely he has the honor of seeing these things up close...  make sure if you have the combination of hardware he mentioned, that the other cylinders may have the same parts... cover that with your mechanic....

Thanks for sharing the details...

PP thoughts only, not a mechanic...

Best regards,

-a-

[M20S Driver]

After a long list of actions, ultra Sonic cleaning of the flow divider solved the problem.   This was one of the most puzzling ones since initially there was no JPI data.  JPI 830 was added after the top overhaul and helped the owner and mechanic find the problem !!!

The SB attached did not apply to the plane but it points to a similar issue.

 

 

SB626A AVStar Flow Divider Inspection.pdf

[carusoam]

Great follow up S Driver!

Reviewing the pictures this time... the tulip shape is really pronounced...

It wasn’t as obvious the first time... one of those trick 3D photograph challenges...

Best regards,

-a-

[bradp]

Wait so was the 1 cyl running at peak during high power operations (due to fuel flow restriction due to metal shaving from $hitty QA for a yet another Lycoming OEM supplier) and that caused pre ignition event? 

Just trying to understand the sequence here. 

 

[M20S Driver]

37 minutes ago, bradp said:

Wait so was the 1 cyl running at peak during high power operations (due to fuel flow restriction due to metal shaving from $hitty QA for a yet another Lycoming OEM supplier) and that caused pre ignition event? 

Just trying to understand the sequence here. 

 

I was not the primary dealing with this problem but that is my guess.  The SB did not apply but the cylinder behavior was the same as described in SB.  CHT temp moved much faster than EGT so perhaps it was close to peak. 

Another interesting and puzzling info was the fact that all cylinder flows matched on the ground with boost pump  (measuring the  fuel collected in separate jars).

[bradp]

Cyl 1+3 and 2+4 share a common intake cam lobe, correct... 

And based on the photos, behavior after valvetrain disassembly, seems unlikely that it was a fuel >> air problem. 

[ArtVandelay]

1 hour ago, bradp said:

Cyl 1+3 and 2+4 share a common intake cam lobe, correct... 

And based on the photos, behavior after valvetrain disassembly, seems unlikely that it was a fuel >> air problem. 

Don’t you mean 1&2 and 3&4 share intake lobes.

[bradp]

Yup my bad.  The opposite side share the lobe. 

[Skyland]

Hi folks.  Back to follow-up on my engine adventure.  My first post in this thread describes the event.

With the engine roughness we thought at first it was a stuck open valve.  Turned out to be a worse problem with the #1 intake valve cupped enough to lose compression in that cylinder.  In an attempt to make the short flight home, we removed the valve rotator cap to get that valve to fully close.  Full power run-up, and take off were normal until about 600 feet when compression again was lost in that cylinder and engine began running very rough.  Same scenario, intake valve #1 cupped even more in that very short amount of time.  (Pic 1 shows the cupping measured at 0.365".  Don't know what a new valve measures but it's not nearly this much). 

A week later we installed a loaner cylinder in another attempt to get the plane home.  Again, run-up and takeoff were normal then engine roughness soon after.  Lost cyl. #1 in flight but was able to continue home to a safe landing.  Pulling the prop through again got zero compression in one cylinder.

So just what is causing a #1 intake valve to melt (tulip) three times?  The Sacramento Sky Ranch Engineering Manual seems to describe this scenario and attributes it to a pre-ignition event possibly caused by magnito cross firing.  Pre-ignition is a very destructive event yet the piston and cylinder appeared fine.  I was close to the 500 hour mag O/H so we installed an overhauled mag.  In taking apart the old mag there was a very suspicious burned spot on the phenolic distributor block (see pic).  We hoped this was the root cause.

I elected to send out all four cylinders to Gibson Aviation for a complete top overhaul since there was about 1300 hours on the factory O/H.  They replaced the #1 tuliped valve, of course, but said all the pistons and cylinders and seats were all in spec.  I elected to go .010 over with new pistons, in part, to improve oil consumption numbers.  Very professional workmanship, I might add.

During the engine downtime I installed a JPI 830 engine analyzer to replace the old school factory single cylinder analog CHT and EGT.

Fast forward another few weeks with engine all back together.  Ground run-ups fine with nice graph and numbers on the new JPI.  First flight takeoff normal until about 600 feet, then the JPI start flashing CHT overheat (see pic).  Cut power and landed.  WTF?  Problem still there, except this time indicating it switched from cylinder 1 to 2.

My IA now suggested the fuel divider.  We did a fuel flow test and all injectors pumped fuel equally into the four jars.  Decided to disassemble the fuel divider for inspection and cleaning.  One of his A&Ps took it apart and threw it in the ultrasonic cleaner before I had a chance to examine it.  I wanted to carefully inspect to see if there was any proof of visible blockage.  But reassembling the divider and reinstalling it on the plane proved successful.  After 14 hours on the engine not a hint of the former problem.  JPI graphs and numbers repeatedly look nice and even.

Problem occurred primarily during climb outs and changed from cylinder 1 to 2.  It's still hard for me to believe an intake valve with relatively cold air rushing past it can be softened by an overheated cylinder without affecting the piston, cylinder or seat.

So a clogged fuel divider seemed to be the culprit causing a lean mixture in one cylinder.  I would think an ultra lean mixture would be way out of a stoichiometric ratio thus causing a cooler incomplete burn.  Apparently not.  Any expertise here to explain this?

Best regards, Ken

[carusoam]

Skyland,

Sharing the graph pic is good, but...

The hard data is hidden....

Can you share the data (button on Savvy) and post the savvy link here..?

Yow...!     EGT2 and CHT2 ran away...

 

The odd thing about engine ping... it is highly destructive... often within minutes...

The aluminum piston crowns often melt... and oil is no longer contained in the engine...

The ping somehow causes a loss of boundary layer at the piston... this boundary layer is responsible to keep the high EGTs from contacting the aluminum surface...

 

It looks like you may have been battling two devils at the same time...

• An ignition one... odd scar in the mag...
• Fuel flow one... cleaning up the fuel divider

How many hours were on each device?

Got any pics inside the cylinder?

Causes of ping or pre-ignition....

• heavy carbon deposits... they glow... and act like a diesel’s glow plug...
• Timing too advanced... ICPs can grow too high before the piston reaches TDC...
• High MP combined with too Low RPM...  

It turns out timing in degrees is not the same as timing in milliseconds... the mechanical engine uses degrees, the flame fronts use milliseconds...

Oddly fuel mixtures go from burning to exploding(?) without the pilot being aware it is happening...

To reshape an intake valve... probably takes some really high temps and pressures.

 

PP thoughts only, not trained in the mechanical arts...

Best regards,

-a-

[carusoam]

Follow-up...

Improving run-up data... this is a test of ignition system health... it gives insight to timing and spark plug variances...

Either your run-up happens too quickly for the monitor to catch the data... or your data collection rate is set too low...

Some monitors use six seconds per data point... change to one second if able...

Some pilots click the switch, get a change, click again... this happens in seconds, never stabilizes, can’t collect the data that could save your engine’s bacon...

Better to use 15 seconds on each click... then miss a hiding mag issue...

Some mag issues get worse at higher altitudes, the air molecules actually work as a resistor... pressurized mags put that resistor back in place... 

PP thoughts only, hoping to see the rest of the data....

Best regards,

-a-

[carusoam]

Something happened at around 9:30...  EGTs go off in all directions... ? (What happened there?)

Some got hotter, some went cooler...

As if the fuel divider went on holiday(?) in reaction to the MP being pulled...
 

With the engine monitor collecting data... nothing really stands out prior to flight...

EGT2 says look at me... but it isn’t screaming...

Until WOT...

PP observations of the graphs above only...

Best regards,

-a-