Mysterious engine/vacuum pump problem

[DonMuncy]

I was leaving Kerrville after the MAPA convention on my way back to Dallas. I climbed to 7000 and was between layers about 30 minutes into the flight when the annunciator light (low/high vacuum) came on. I watched for a minute and sure enough, the HSI started to go up. I was on AP and it started to descend. Not long after, the engine began running rough.

I declared an emergency, and asked for help getting down through the clouds, not knowing how low they went. I broke out at about 2000 to 2500.

At that point, the closest runway was Spicewood (88R). I landed there.

My luck was great as an A&P was there working on his hangar door. When I got out, there was oil all over the nose wheel. While I was there, we found the vac pump drive was sheared. After I left, he called and said I had one cylinder full of oil. The source of the oil leak was a blown rocker cover gasket.

His wife gave us a ride to a rent-a-car place which happened to be open on Sunday, and we drove on to Dallas.

Today we took the rented car back and went by to check on the plane. The A&P showed me some strange looking stuff in the oily cylinder with his borescope. I suggested we pull the rocker cover and see if we could see anything. The screws on the cover with the bad gasket were only finger tight. When the cover came off, I looked and saw that the rocker wasn’t sitting squarely on the end of the valve. I reached up to see if the rocker would move. The rocker and the chunk of the cylinder head it attaches to came off in my hand.

So far we are at a vacuum pump and a replacement cylinder. He is going to take the cylinder off and see what else is going on.

I am at a loss as to what can break the top off the cylinder head and shear the vacuum pump drive. (Remember this is a 6 cylinder Continental, as you help me think through this.) I really don’t like coincidence as an explanation.

What do our resident gurus think.

[DonMuncy]

I didn't mention that this kills any possibility of flying my plane to the AOPA event Saturday. If anyone is going down from the Dallas area, I would gladly contribute, for a ride.

[N201MKTurbo]

Hummmmm.... Without directly seeing the engine it is kind of hard to tell. Perhaps the leaking oil got on the vac pump shaft and migrated into the pump and caused it to lock up. Was there a lot of oil on the pump?

[DonMuncy]

Didn't seem to be a lot, and the vac loss happened before the engine roughness.

[N201MKTurbo]

Just can't imagine the pump breaking your cylinder..

Sorry to hear about your troubles.

I always tell people the difference between an aircraft renter and an aircraft owner is:

If an aircraft renter hears a big noise up front he thinks "I'm going to die". The aircraft owner thinks "what is this going to cost me"

I hope the trouble is limited to the bad cylinder.

[cliffy]

You say the rocker wasn't hitting squarely on the center of the valve stem? A couple of thoughts come to mind.

Has the engine been overhauled lately?  Has that cylinder been off recently? Could the wrong rocker arm have been installed on that side of the cylinder?

Is the rocker on the other side of the cylinder hitting on center or off center? Maybe they were swapped from side to side. I would look into the other side and see what's there.

With the rocker cover loose, that tells me someone was in there recently. That is why I surmise that the rockers were swapped from side to side in the cylinder head. Really need to know what has been done to this cylinder recently. 

I presume the chunk of cylinder that came off was part of the boss that the rocker shaft goes through? If so it could have been compromised by the off center hitting of the valve rocker. 

You say there is something "inside" the cylinder? Please let us know what it is when the cylinder comes off. 

I can't think of anything that is concomitant with a cylinder and your vacuum pump. The two may not be connected.

You are one lucky flyer. Sounds like you did everything as good as it could be done in flight under IFR conditions. Very well done my friend!. 

[cliffy]

BTW  How much time does the vacuum pump have since installed? 

[BobAustin]

Don,

 

Just saw your post.  Don't know what the cause was...maybe too much Bill's BBQ.  Just kidding... glad you are ok and could handle the emergency.  I live in Austin near Lakeway (30 min drive to Spicewood) and if you need help let me know.  Spicewood has lots of active pilots and I am sure you will get good mechanical help there.  I have some contacts there so give me a call.

 

Bob Yarbrough

[231flyer]

Glad you are ok and made a successful emergency landing.  

 

My 231 has an AirWolf Oil Separator that is connected to the vac on the outflow side.  Many years ago my vac shaft sheared off (seems this only occurs in IMC) and I too had to declare an emergency and land in Paducah KY.  The loss of vac resulted in the oil separator blowing oil/smoke into the cabin and also caused considerable engine roughness.  I remember thinking I was going to lose the engine once I had opened the vents and cleared the smoke.  It turned out to be a simple vac failure (right at 500 hrs TT) and the local mechanic had a replacement in stock. The engine test ran smoothly after the replacement and he thought the rough engine was caused by the loss of pressure to the oil separator.  Anyways the fix worked and I was able to continue on from Dayton to Corpus Christi. Obviously I don't have all the details, your two issues might be unrelated but co-incident.   

 

Btw Sal's Aircraft Cylinder service in Prosper (214) 630-7880 does great work and I had my TSIO 360LB topped in 2007.  All cylinders still hold 76" or better.

[BobAustin]

Don,
If you need it I have a friend at 88R with plenty of hanger space. Need your contact info.

Bob Yarbrough

 

[takair]

Can't really speak for what happened to the engine, but it does not take much oil to fail a pump. They just do not tolerate much contamination. Is it possible that the cylinder started having issues and leaking prior to rough running? Was there evidence of oil on the pump, even if it was only a film?

[Piloto]

It looks to me that the initial cause of cylinder failure was due to loose cover screws that caused oil to drain out of the valve stem. This would have caused a stuck valve condition that would have pulled the rocker attachment. It is not unusual for valve cover screws to get loose with time as the gasket compress. Screws should always be retightened at every annual. Rubber orange gaskets are better  than the cork gaskets and last much longer. You may need to check the camshaft lobes thru the lifter holes.

 

I think the pump failure was coincidental. But the pump and the cylinder are interconnected thru the camshaft. Did you experience any sort of backfiring when the pump failed? Must likely the rubber coupling in the pump failed and not the pump inside. These couplings failures are common as they get old. You can test the pump by mouth by just sucking on the outlet port. It should rotate freely. It will not rotate with the pump attached to the engine.

 

José    

[DonMuncy]

Thanks for all the replies. I appreciate all the help I can get.

As to the rocker arm not hitting the valve squarely; that was only because the place where it attaches on the cylinder head was broken off. Otherwise, it seemed as though it was working well.

I assume the engine started running rough instantly when the rocker mount broke, and further assume the gasket on the rocker cover was not leaking before the mount broke, so I have difficulty seeing the oil leaking out could have caused the vac pump failure.

But you know what they say about assuming things. I really don't know.

My vac pump has almost 600 hours on it as a rebuilt unit.

The cylinder was installed as a "serviceable" unit about 700 hours ago. But 110 hours ago, the cylinder was overhauled due to low compression. This is before I learned about the Continental SB about low compressions. I would/will NEVER again allow someone to change or overhaul a Continental cylinder based solely on low compression.

I have no idea about what the stuff is in the cylinder. It appeared like a white granular substance, but the borescope picture didn't appear that good.

I also have questions about how bad the oil in that cylinder was. It could have been exaggerated a little to me.

If we can accept two separate failures within a very short time of each other, or that somehow the rocker mount failure was happening over a period of time, and that caused the vac failure before the rocker mount completely broke and caused the roughness a few minutes later, then everything would be explained.

The A&P has some other pressing stuff going on, and he is virtually a one man shop, so it may be a couple of days before I learn anything else.

I will continue to post as we learn more.

Keep the suggestions coming.

[DonMuncy]

I didn't address the loose rocker cover screws. I am not too happy about that, as I only have about 12 hours since the last annual. But I had not seen any evidence of oil loss before Sunday.

[Marauder]

If you had Lycoming, I would have surmised the white granular was the sodium from a sodium filled valve. Be interested in hearing why/what is found to be the root cause. Glad to hear you safely landed!

[cliffy]

You are correct on your comment about low compression given Continentals take on the issue. It all depends on where it is leaking from. 

Have your vac pump checked to see if it came apart internally. You may have reached its service life as a rebuilt even considering the warranty that they normally give on them. How old was the pump? Years?

I'm still going back to cylinder work on the failure. Loose screws at 12 hrs?  Hmmmmm! Does the inside of the rocker cover show and marks of being hit by the rocker arm? 

110 hrs on an overhaul?  Was any indication of total hrs on the cylinder given when you first installed it as a serviceable unit 700 hrs ago? Could have had thousands of hrs before you got it. Was it ground oversize when you got it? Was it standard size? 

[PTK]

I'm very glad you handled the emergency and landed safely Don. The rest can be worked out.

Great job.

There's truth to cork vs silicone gaskets Jose mentioned. Before I changed to silicone invariably I'd find a cover screw here or there looser than the rest. Now that is not the case.

[DonMuncy]

Cliffy,

The overhauled vacuum pump was installed in 2001, so I don't have any real issue with its failure. (It could have timed itself better; like when VFR).

It has not yet been removed, but I can see that the "engine side" of the shaft is turning, but the "pump side" is not.

I don't recall seeing marks on the inside of the valve cover, but I wasn't looking that close.

I do not know whether the cylinder was oversize. The "serviceable" cylinder was put on before I bought the plane, and we have no idea about its history.

I agree with your skepticism about the loose screws so soon after annual. The red silicone gasket appeared to have "blown out" on one side of the cover, and I don't know what to make of that.

[larryb]

Cliffy,

The red silicone gasket appeared to have "blown out" on one side of the cover, and I don't know what to make of that.

I am thinking you must have had a lot of crankcase pressure to do that.

Are there any dents on the rocker cover from the inside? Another mystery is the oil reported in the cylinder. How did it get there? I don't see how the broken rocker support would have caused that.

Sent from my iPad using Tapatalk

[DonMuncy]

When I get back down there, I will look better at the cover for dents. I'm with you, I don't see pressure blowing it out. More like mechanical force pushed it out.

More questions, few answers.

I will post more as I learn more.

[DonMuncy]

Now the cylinder has been removed. It is obviously trash and an overhauled one is on order, as well as a replacement vacuum pump. Photos of the cam and lifters have (tentatively) passed muster with Continental.

But the A&P has cut open the filter and found some metal (magnetic). From his description, it is less than 1/4 teaspoonful, an amount that Continental says should warrant flying an additional 10 to 15 hours, change the oil and check again.

At this point, I am leaning toward coincidence as the cause for two unrelated failures within a few minutes of each other.

I'm still open to suggestions.

[jetdriven]

I'm wondering if a valve could have stuck allowing the piston to bang the valve and crack the casting boss for the rocker shaft.

[Jeff_S]

I'm wondering if a valve could have stuck allowing the piston to bang the valve and crack the casting boss for the rocker shaft.

 

Admittedly, I know next to nothing about engine parts, but am I the only one who thinks the above sentence is more than slightly pornographic?

[DonMuncy]

Had an interesting follow-up on my problem today. I got a call from the San Antonio FSDO. He said he was following up on my emergency declaration. He said it was his responsibility to make sure the situation was not pilot error, necessitating a check ride. He wanted the name and telephone number of the A&P, and said he would probably request a copy of the log book entry.

It was my impression that declaring an emergency was not a problem unless other traffic had to be "interrupted" due to my declaration. I didn't think my situation caused any disruption, but am not certain.

[Marauder]

What is happening to our world? In the old days, they would have handed you a cigarette and said "Nice job Don getting 'er down in one piece".

 

Here are the regs on what follow-ups:

 

§ 91.3 Responsibility and authority of the pilot in command.

 

(a) The pilot in command of an aircraft is directly responsible for, and is the final authority as to, the operation of that aircraft. 

 

(b)In an in-flight emergency requiring immediate action, the pilot in command may deviate from any rule of this part to the extent required to meet that emergency.

 

© Each pilot in command who deviates from a rule under paragraph (b)of this section shall, upon the request of the Administrator, send a written report of that deviation to the Administrator. 

 

§ 91.123 Compliance with ATC clearances and instructions.

 

(a) When an ATC clearance has been obtained, no pilot in command may deviate from that clearance unless an amended clearance is obtained, an emergency exists, or the deviation is in response to a traffic alert and collision avoidance system resolution advisory. However, except in Class A airspace, a pilot may cancel an IFR flight plan if the operation is being conducted in VFR weather conditions. When a pilot is uncertain of an ATC clearance, that pilot shall immediately request clarification from ATC.

 

(b)Except in an emergency, no person may operate an aircraft contrary to an ATC instruction in an area in which air traffic control is exercised.

 

© Each pilot in command who, in an emergency, or in response to a traffic alert and collision avoidance system resolution advisory, deviates from an ATC clearance or instruction shall notify ATC of that deviation as soon as possible.

 

(d) Each pilot in command who (though not deviating from a rule of this subpart) is given priority by ATC in an emergency, shall submit a detailed report of that emergency within 48 hours to the manager of that ATC facility, if requested by ATC.

 

(e) Unless otherwise authorized by ATC, no person operating an aircraft may operate that aircraft according to any clearance or instruction that has been issued to the pilot of another aircraft for radar air traffic control purposes.