Camshaft / Morning Sickness / Sticky Valve

[mschmuff]

I’m hoping someone here can give me some insight to my current issue.  And I have read a bunch of other posts on this topic.

 

For the last 10hrs on my ’67 M20F (500hrs SMOH) I have had what could be described as “morning sickness”.  I start the plane (always preheated) and let the oil temp get up to 100 / cyl 275.  No roughness on start up or idle.  Sometimes when I take off the engine runs rough but within 30 seconds smooth’s out for the rest of the flight.  JPI shows the #1 cyl not coming up to temperate and even sometimes getting colder until it stops running rough.  We figured on a sticky valve.  Sometimes it would run perfectly on take off – no roughness what so ever.  Cruise flight and landing are always fine.

 

My mechanic pulled the valve cover and inspected the #1 cylinder but could find nothing wrong.  Continued flying it for 5 more hours but the problem did not go away.  Climbing out on 3 cylinders is no fun so I took the plane back to my mechanic.  He pulled the cylinder completely and said the Cam is bad and the lifters are spalling…….WTF?

Now here is the kicker…….as some of you know, this plane had a deer strike and a complete Tear Down Inspection in December of 2013.  If my cam was inspected and/or sent out for the TDI - how in 11 months and 100 hours could the cam/lifters fail?  Is this even possible?

1. Did the cam/lifters not get inspected?
2. Were they not reinstalled properly?
3. Was everything dome properly and I am seriously just that unlucky?

[kmyfm20s]

Did they replace any parts on the tear down, Lifters? Maybe some inferior parts where introduced. I wonder if there is some type of warranty if so. That really stinks because obviously you would rather pony up for the extra money of the overhaul at that time.

[carusoam]

It is possibly a sticky valve...

With the JPI, you have identified the cylinder...

It is usually the exhaust valve...

The valve guide cleaning procedure is sometimes called the "rope trick"

Ask your mechanic what this would entail.

Good luck,

-a-

[Marauder]

Take a look at the inspection log for the deer incident. There should be a notation to either what was inspected or a reference to the procedure followed. Something like "inspected according to Lycoming's XXX procedure". If the procedure is referenced, I would get a copy of it and review it.

As for the morning sickness, bnicollete posted a thread on his morning sickness problem. It has a picture of the JPI view of it. You can also have the Savvy Aviator site look at the data as well to get their thoughts.

[Marauder]

BTW -- you never came up to see my Aspens. I know you are pretty busy. Let's make some time after you get through this situation.

[N601RX]

Is only #1 spalled? Continuing to run with a sticking valve can damage the lobe on that goes to that valve.

[Apexheli]

I have seen cams can be fine at one oil change and within 50hrs start making metal. Just experienced the same thing on one of my helicopters (IO-540). Flew weekly, 600TT, oil changed every 25hrs and filter on the 50, etc. Started making metal from one cam lobe and cam follower. Its a Lycoming, they are known to have cam issues.

[Browncbr1]

I'm sure you already knew, but I've been told to idle 1100-1200 rpm in order to keep the cam wet with oil... Not sure i this came into play, but thought I would mention it as a possible cause?

[mschmuff]

Thanks for the responses.  The engine is out and the cam is being replaced.  I am told that the sticky valve could not cause the cam to make metal.  Basically in a metal on metal fight the cam is definitely not the weakest link - something else would break.  Bent push rod, etc.  Coincidental that the lobe under the cylinder that was giving me trouble is the only lobe going bad.  I don't know enough about engines to answer that.

Hope to be back in the air soon - this driving to work sucks!!

[N601RX]

Many well respected Lycoming experts have came out and said a sticking valve can damage the cam. Here is one below.

Complete article here. http://www.avweb.com/news/maint/182894-1.html?redirected=1

"What happens whan a valve sticks?

When an engine has a stuck valve, one of five things can happen, each of which is bad news:

The pushrod bends.

The surface of the camshaft or cam follower fails.

The valve opens but won't close.

The rocker support breaks.

The valve rotator cap falls off the end of the valve stem. (Lycomings only.)

A valve that sticks closed will often result in serious and costly engine damage. Each time the cam-tappet-pushrod-rocker try to open that stuck valve, you risk catastrophic engine damage. With a stuck valve, the valve doesn't want to move. Tremendous valve train forces develop as the camshaft lobe tries to force the valve open. The camshaft follower and lobe are the most highly-stressed components of the engine even under normal conditions...the additional loading caused by a stuck valve may induce catastrophic failure of the rocker support, pushrod, cam follower, or cam lobe.

A damaged camshaft lobe requires complete engine removal and teardown. The same is true of a damaged cam follower if it is the mushroom-head variety used in many Lycoming engines.

Sometimes an exhaust valve that is stuck closed can cause the intake pushrod to bed or the intake rocker support boss to break. How can this happen? If the exhaust valve sticks closed, exhaust gases will not exit from the cylinder. Gas pressure within the cylinder then prevents the intake valve from opening. If this happens, something's gotta give. Either the pushrod bends or the rocker support breaks.

You might think that a valve that sticks open is a much less serious situation, but that's not necessarily so. If the valve is an intake valve, you lose power and will need to make a forced landing. If the valve is an exhaust valve, there will not be any compression on that cylinder.

In either case, if the valve spring can't close the valve, the entire valve train (cam follower, pushrod, and rocker arm) unloads. The end of the pushrod that rests in the socket in the cam follower may come out of the socket and fling around inside the tappet boss. If the pushrod ball does not locate itself back into the socket when the cam lobe comes around, it may jam against the tappet housing, usually causing crankcase damage.

The valve rotator cap on Lycoming engines is kept on the tip of the exhaust valve stem by the rocker arm. If the valve sticks open, the rocker may move far enough away to allow the rotator cap to fall off the valve stem tip. When this happens, not only is valve clearance excessive, but also the rocker face pounds into the spring seat. The rotator cap is too big to fall down the pushrod tubes. It just lays in the rocker box until you take the rocker box off. It then quietly falls unnoticed onto the hangar floor. If you notice a missing rotator cap, it is likely that the exhaust valve was stuck open in the past. Look in the rocker box or around the hangar floor and you might find it.

Engine damage does not always occur when the valve sticks, but the longer the engine operates in this condition, the greater the chances are that some damage will occur."

[bnicolette]

Take a look at the inspection log for the deer incident. There should be a notation to either what was inspected or a reference to the procedure followed. Something like "inspected according to Lycoming's XXX procedure". If the procedure is referenced, I would get a copy of it and review it.

As for the morning sickness, bnicollete posted a thread on his morning sickness problem. It has a picture of the JPI view of it. You can also have the Savvy Aviator site look at the data as well to get their thoughts.

Chris Chris Chris!!  It's bnicolette.  

 

Here is the thread:

 

http://mooneyspace.com/topic/9525-sticky-valve-lycoming-io-360-a3b6d/?hl=%2Bmorning+%2Bsickness

[mschmuff]

Good article!!  Thank you.

 

Ok - next question.  I see that a sticky valve can cause the cam issue.  How about the inverse??

Will a bad cam present itself as a stuck valve??

Again, I start up - runs smoothly.  Go to take off and under full power the number 1 cylinder fails.  I have to assume the answer is yes since I am being told that my cylinder is fine and my only problem is a bad cam........right??? 

 

I'm sure you can see my concern.....I replace the cam/berrings/lifters/etc, we don't do anything to the cylinder and we still have the same problem as when we started this entire excersize!!

[carusoam]

I would not suspect a cam to be able to stick a valve...

My O360 stuck the exhaust valve. The piston (evidence... mark on piston) supplied the force to bend the valve...

Degraded/burned/carbonized oil is known for causing valves to stick...

The bent valve can get stuck (partially) closed after that...

Evidence(JPI) of sticky valves is a call for further investigation/cleaning....

A worn cam may make it look like a stuck valve?

Seems like you have covered many bases.

At start-up, do you here an odd valve clank. One can sound different than the others. It will stand out enough that a PP's parents will ask "is that normal?".

Hope that helps...

PP advice, I am not a mechanic...

-a-

[N601RX]

Good article!!  Thank you.

 

Ok - next question.  I see that a sticky valve can cause the cam issue.  How about the inverse??

Will a bad cam present itself as a stuck valve??

Again, I start up - runs smoothly.  Go to take off and under full power the number 1 cylinder fails.  I have to assume the answer is yes since I am being told that my cylinder is fine and my only problem is a bad cam........right??? 

 

I'm sure you can see my concern.....I replace the cam/berrings/lifters/etc, we don't do anything to the cylinder and we still have the same problem as when we started this entire excersize!!

 

 

The cylinders and valve guides need to be checked out really well and figure out why the valve was sticking. They can look for carbon when removing the valves.  The guides/valves will need to be replaced if worn. If the valve to guide clearances are all within spec, then start looking at other areas as operational Cht's on that cylinder, not leaning, not enough oil flow to the valves/rockers, worn rocker arms and thrust washers creating sideload on valves ect.  There have been discussions that the new style lifters do not provide as much oil to the rocker box area as the old ones.

[Andy95W]

I know everyone loves Camguard, but there has been a fair amount of evidence (mostly anecdotal, I agree) that Lenkite Avblend helps in preventing valve sticking.

I rotate using Avblend and Camguard every oil change, trying to get the best of both worlds.

[Piloto]

I had a similar problem when I switched from Aeroshell 20W-50 to Exxon Elite. The problem appeared to be lifter lack of oil retention before engine start. This would cause the lifter not to open the valve thus roughness during the first 15 seconds. I switched back to Aeroshell and problem solved. The oil need to have some degree of viscosity so it will not drain out of bearings and lifters after shutdown.

 

José

[Guest]

I have seen cams can be fine at one oil change and within 50hrs start making metal. Just experienced the same thing on one of my helicopters (IO-540). Flew weekly, 600TT, oil changed every 25hrs and filter on the 50, etc. Started making metal from one cam lobe and cam follower. Its a Lycoming, they are known to have cam issues.

It not just a Lycoming issue anymore. Over the last few years we've seen more TCM 520/550 series engines with spalled lifters. The saving grace is that caught in time you can replace the lifters and save the cam.

Clarence