O-200-A stuck exhaust valve.

Greenhead

Greenhead

Pre-takeoff checklist
Joined
Nov 25, 2014
Messages
113
Found yesterday evening that #4 exhaust valve seems to be stuck open. Mechanic and I were doing compression checks and had 73-74-73/80 on first 3 Cold. Nothing on #4. Buttoned things up and ran engine until oil temperature came up and checked again with no change.

Little history:
Purchased plane (C150L) last year after it had not flown for 8 years. Owner had been running engine throughout the years but had lost medical. Prebuy and annual compressions were all around mid 70's.

So questions I have, is there anything else I need to try and check? Look for? Purchase new cylinder or rebuilt? Any other helpful information will be appreciated.

Just a new pilot in training learning the hardships of aircraft ownership. Little engine ran good with only 3 cylinders though.


I want to Die with Memories, Not Dreams!
 
Greenhead said:
Found yesterday evening that #4 exhaust valve seems to be stuck open. Mechanic and I were doing compression checks and had 73-74-73/80 on first 3 Cold. Nothing on #4. Buttoned things up and ran engine until oil temperature came up and checked again with no change.
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What tests did you perform to determine that it is the exhaust valve that is stuck? Hissing through the exhaust when pressurized? What?

It doesn't matter which valve, though. Remove cylinder. Ream/clean valve guide. Check valve stem for straight. Lap valve back in. Two hours mechanic time tops.

Jim
 
Yes, hissing through exhaust. Was thinking myself it should be a fairly cut and dry fix but AP/AI (friend) wasn't to keen on attempting. Wanting to fix as safely and low budget as possible. Having trouble researching and finding price for rebuilding mine.
 
weirdjim said:
What tests did you perform to determine that it is the exhaust valve that is stuck? Hissing through the exhaust when pressurized? What?

It doesn't matter which valve, though. Remove cylinder. Ream/clean valve guide. Check valve stem for straight. Lap valve back in. Two hours mechanic time tops.

Jim
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Your hours are a lot bigger than mine. The baffling has to come off, the exhaust, then the base flange nuts, and only then can the real work start. And then all the reassembly. Takes me a lot more than two hours.

Dan
 
Greenhead said:
...Little engine ran good with only 3 cylinders though...
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I'd say you don't have a stuck valve then because an O-200 definitely does not run "good" on three cylinders.
 
Dan Thomas said:
Your hours are a lot bigger than mine. The baffling has to come off, the exhaust, then the base flange nuts, and only then can the real work start. And then all the reassembly. Takes me a lot more than two hours.

Dan
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Seems like I always find something else that needs attention in the process. Then there are rusty fasteners that I likely don't have on hand etc.
 
Might be stuck. Might be burned. Might be a bad lifter or cam. The mechanic has more work to do before you can decide how to fix it.
 
Stewartb said:
Might be stuck. Might be burned. Might be a bad lifter or cam. The mechanic has more work to do before you can decide how to fix it.
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How does a bad cam or lifter give you zero compression?
 
Silvaire said:
I'd say you don't have a stuck valve then because an O-200 definitely does not run "good" on three cylinders.
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Agreed,, He most likely has a worn guide allowing the valve to seat wrong each time it closes.

I'd pull the rocker shaft, and do a spring tension check, and a valve wobble check.

Bring the piston to TDC apply air, and wiggle the valve stem, see what hissing does. you'll hear it change when the guide is worn.

any movement beyond .002" you should simply change the cylinder for a new one.
 
If indeed the valve is stuck and not burnt it can be freed up with the old "rope trick" with the cylinder in place. Ask around for an old fart mechanic.

Paul
Salome, AZ
 
pmanton said:
If indeed the valve is stuck and not burnt it can be freed up with the old "rope trick" with the cylinder in place. Ask around for an old fart mechanic.

Paul
Salome, AZ
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IF in fact this valve is stuck open, it can't be open much, or the piston will strike it, and force it closed. then the push rod will bend when it tries to open it again, if it does open the piston will hit it again, closing it, there it will stay.

When the valve is stuck open, and the piston hits it, it will bend the valve stem, then it will never close again, and in most cases I've seen it will loosen the guide and ruin the cylinder head.
 
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The results of the only really stuck valve I've seen in a 0-200 in a long time.
 

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Tom-D said:
any movement beyond .002" you should simply change the cylinder for a new one.
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Ummm why new cylinder? Aren't valve guide bushings replaceable? What happened to IRAN? All else being in good order just fixing that one valve like someone above suggested should be enough, no?
 
Not an A&P, but, I'd stick my camera in there and take a look at it..since that would take me about a minute to do. Would then likely try to lap it in place given the fact that I could do that with little effort or disassembly.

In my case, when I had an issue like this on my A75, it turned out to be a crack through the valve seat.
 
LuisO said:
Ummm why new cylinder? Aren't valve guide bushings replaceable? What happened to IRAN? All else being in good order just fixing that one valve like someone above suggested should be enough, no?
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Finding any A&P that will just repair what's wrong with a cylinder is the problem.
Every body wants to complete the overhaul, simply because of they know it is a short time repair. and the overhaul on a 0-200 cylinder is as much as a new ECI

Penny smart pound foolish type thing.
 
pmanton said:
If indeed the valve is stuck and not burnt it can be freed up with the old "rope trick" with the cylinder in place. Ask around for an old fart mechanic.

Paul
Salome, AZ
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The colloquialism for that is called a (politically incorrect term) valve job. Leaded avgas on small bore Continentals is well known.

Jim
 
weirdjim said:
The colloquialism for that is called a (politically incorrect term) valve job. Leaded avgas on small bore Continentals is well known.

Jim
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Go to Aircraft Specialities and price out, two new valves, 1 piston, one piston pin, a set of rings, two valve seats, two new over sized guides, two outer valve springs, two inner valve springs, then add 8 hours of machine time plus the man hours at $150per hour to hone the cylinder, remove and replace the seats and guides. then you'll know why no one overhauls the TCM 50CI cylinders. at $900 (+-) bucks each.
Only to have them crack 200 hours later.
 
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jesse said:
Not an A&P, but, I'd stick my camera in there and take a look at it..since that would take me about a minute to do. Would then likely try to lap it in place given the fact that I could do that with little effort or disassembly.
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this, get a $40 USB Dental camera and have a look-see first.....IMHO. :yes:
 
Tom-D said:
IF in fact this valve is stuck open, it can't be open much...
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It might be just a bit of carbon stuck to the valve face or seat. Rocker cover off, pressure on cylinder, tap the exhaust rocker with a soft hammer to dislodge it.

Dan
 
Tom-D said:
Go to Aircraft Specialities and price out, two new valves, 1 piston, one piston pin, a set of rings, two valve seats, two new over sized guides, two outer valve springs, two inner valve springs, then add 8 hours of machine time plus the man hours at $150per hour to hone the cylinder, remove and replace the seats and guides. then you'll know why no one overhauls the TCM 50CI cylinders. at $900 (+-) bucks each.
Only to have them crack 200 hours later.
Click to expand...

Go to Home Depot and price out two feet of 1/2" cotton rope and two feet of 0.020" safety wire, Then a couple of hours of time using an electric drill and cutting fluid/acetone to melt the lead deposits out of the guide, a standard size reamer to get the smooth sides on the guide, all back together and THEN wait for them to crack. And of course they will. THEN time for new aftermarket cylinders (NOT that Continental Crap).

Jim
 
Dan Thomas said:
It might be just a bit of carbon stuck to the valve face or seat. Rocker cover off, pressure on cylinder, tap the exhaust rocker with a soft hammer to dislodge it.

Dan
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We tried that but made no difference. Had my fingers crossed.

So, would the best move be to bite the bullet and purchase new cylinder? Then rebuild my original as a spare, assuming that it's a seat problem and nothing else. Trying to go smartest route for the money. Like most, flying on a tight budget with myself and 15yr old daughter using to get ppl. Safety first with her also.

Just trying to weigh out options before jumping.


I want to Die with Memories, Not Dreams!
 
weirdjim said:
What tests did you perform to determine that it is the exhaust valve that is stuck? Hissing through the exhaust when pressurized? What?

It doesn't matter which valve, though. Remove cylinder. Ream/clean valve guide. Check valve stem for straight. Lap valve back in. Two hours mechanic time tops.

Jim
Click to expand...

Might take someone else longer but the cure is correct. Look no further.
 
Someone who knows what they're doing can drop the offending valve into the cylinder, clean up the valve stem and valve guide (with correct reamer), put it all back together--all without pulling the cylinder. This would be the most cost effective repair if the valve is sticking due to crud buildup in the guide. It doesn't solve a problem with the valve seat or a guide that is unevenly worn and causes the valve to wobble. I would stay away from solvents because it's difficult to be sure that all the crud has been removed and any remaining crud may cause uneven wear on the valve guide.

If you're not a member of the Cessna 150-152 club, you ought to be. There are some pretty knowledgeable folks that contribute to the club forum whose advice is probably worth more than what you will get on POA.
 
Marvel mystery oil vs the rope trick

I know I'll get hated on but I've seen MMO make a dramatic difference
 
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taters said:
Marvel mystery oil vs the rope trick

I know I'll get hated on but I've seen MMO make a dramatic difference
Click to expand...

I believe MMO is better at keeping a clean valve stem and guide clean than curing a problem that has already made itself evident. Once the guide and or stem has collected deposits (lead or carbon), it's best to remove the deposits mechanically rather than rely on a chemical solution.
 
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Witmo said:
Someone who knows what they're doing can drop the offending valve into the cylinder, clean up the valve stem and valve guide (with correct reamer), put it all back together--all without pulling the cylinder. This would be the most cost effective repair if the valve is sticking due to crud buildup in the guide. It doesn't solve a problem with the valve seat or a guide that is unevenly worn and causes the valve to wobble. I would stay away from solvents because it's difficult to be sure that all the crud has been removed and any remaining crud may cause uneven wear on the valve guide.

If you're not a member of the Cessna 150-152 club, you ought to be. There are some pretty knowledgeable folks that contribute to the club forum whose advice is probably worth more than what you will get on POA.
Click to expand...
I've done the rope trick many many times it is but a temporary fix. If it coked up once, it will do it again.
 
Witmo;1830218[PHP said:
If you're not a member of the Cessna 150-152 club, you ought to be. There are some pretty knowledgeable folks that contribute to the club forum whose advice is probably worth more than what you will get on POA.
Click to expand...

I've yet to see a type club that didn't have its self appointed expert.
 
weirdjim said:
a standard size reamer to get the smooth sides on the guide, Jim
Click to expand...

Throw the reamer away, and come into the 21st century and get a diamond flex hone.

Flood it with WD40, spin it at 600-800 RPM on your electric drill motor, push it in and pull it out once your done.

They will leave a better finish in the guide than any reammer you've ever seen.
 
Tom-D said:
Throw the reamer away, and come into the 21st century and get a diamond flex hone.

Flood it with WD40, spin it at 600-800 RPM on your electric drill motor, push it in and pull it out once your done.

They will leave a better finish in the guide than any reammer you've ever seen.
Click to expand...

Tom, I haven't done a M*x***n valve job in twenty years. I'm busy enough doing avionics approvals and owner annuals I don't have TIME to do stuck valves although I do remember how to do them.

I can't afford a diamond hone for something I *might* do one of in the next five years.

Thanks,

Jim
 
weirdjim said:
Tom, I haven't done a M*x***n valve job in twenty years. I'm busy enough doing avionics approvals and owner annuals I don't have TIME to do stuck valves although I do remember how to do them.

I can't afford a diamond hone for something I *might* do one of in the next five years.

Thanks,

Jim
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A lot of better tools have been invented in the last 20 years :)
 
weirdjim said:
I can't afford a diamond hone for something I *might* do one of in the next five years.
Thanks,
Jim
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Package of 12, $14 bucks

http://www.grainger.com/product/OSBORN-Flex-Cylinder-Hone-33PM69?s_pp=false&picUrl=//static.grainger.com/rp/s/is/image/Grainger/33PM69_AW01?$smthumb$
 
Tom-D said:
Package of 12, $14 bucks

http://www.grainger.com/product/OSBORN-Flex-Cylinder-Hone-33PM69?s_pp=false&picUrl=//static.grainger.com/rp/s/is/image/Grainger/33PM69_AW01?$smthumb$
Click to expand...

Now THIS is the kind of stuff we need more of in this forum. I didn't even know these things existed, much less being on the order of a buck apiece.

Thanks for the info ... goes into my keepsie file.

Jim
 
weirdjim said:
Yeah, except that a little digging reveals that they are NOT a diamond hone, but silicon carbide, and that they are $14 apiece and you've gotta buy 12 of them at a time.

Jim
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I read that as 1 package of 12 was $14.00

what ever--

That link was for reference as for what to buy. you buy the size for your engine, from NAPA 1 is all you ever need.
 
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Doesn't the silicon carbide end up charging the soft (bronze?) guide with abrasive particles? A reamer has the advantage that it doesn't leave any non-metallic stuff behind.
 
nrpetersen said:
Doesn't the silicon carbide end up charging the soft (bronze?) guide with abrasive particles? A reamer has the advantage that it doesn't leave any non-metallic stuff behind.
Click to expand...

Yes, you do have to clean up after.
 
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