Stuck Valve

timwinters

timwinters

Ejection Handle Pulled
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Feb 23, 2008
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Conway, MO
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LTD
So, last weekend, when I started the plane up after it sat for three days it had a stuck valve. It "cleared" in about 15...20 seconds and everything was fine. (Shut down and inspected to make sure before continuing).

This is about the third time this has happened in the last 300...400 hours.

So, my question is, is there any "legal" detergents that might help clean things up...that one can add to the oil, run for (say) 4 hours or so, and then do an oil change?

Any that actually do good? I'm told STP is a legal additive (the blue bottle) but don't know that for sure and don't know if it does any good.

If no "legal" ones...then are they are good "not so legal" ones? MMO?

I used to use CD2 oil detergent in the old days when car engines were far less sophisticated than they are today and it worked well. I can't find it though...been to a half dozen auto parts stores and no one carries it any longer.
 
The valve stuck because it wasn't getting the proper lubrication, adding a snake oil isn't going to get in there either.
 
I wouldn't fly in that plane until it was fixed, bad ju ju, you're going to be sorry.
 
If your engine is OK, STP and / or a little MMO is not likely to do any harm. But they won't fix a sticky valve.

There is a reason that call that isle in the auto parts store "wishful thinking".
 
PaulS said:
I wouldn't fly in that plane until it was fixed, bad ju ju, you're going to be sorry.
Click to expand...

I've put 14 hours on it already since...no issues...thanks for the concern but that wasn't the question.

Tom-D said:
The valve stuck because it wasn't getting the proper lubrication, adding a snake oil isn't going to get in there either.
Click to expand...

And it's not getting the proper lubrication why? That's the question. And what can be done to rectify the situation?
 
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You know it's a stuck valve how?
 
And it's not getting the proper lubrication why? That's the question. And what can be done to rectify the situation?[/QUOTE]

It is a design defect of both major engine manufacturers, the valve stem is too hot. this carbonizes the oil before it can lubricate. The carbon then sticks to the stem and sticks the valve to the guide , which is now not large enough to allow the valve to slide thru.
 
Clark1961 said:
You know it's a stuck valve how?
Click to expand...

Chug, chug, chug, then smooths out and will operate normally the rest of the day. it commonly known as morning sickness.
 
Tom-D said:
Chug, chug, chug, then smooths out and will operate normally the rest of the day. it commonly known as morning sickness.
Click to expand...

Exactly, I could hear it click when I was turning the engine over...two clicks...then it started. Then rough running for about 15 seconds then it 'unstuck".

Like I said in my OP, it's done this about three times in its life...all three in the last 300 hours or so and in each case it has "unstuck" very quickly...in less than 30 seconds. So it's hard to diagnose.
 
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It is a design defect of both major engine manufacturers, the valve stem is too hot. this carbonizes the oil before it can lubricate. The carbon then sticks to the stem and sticks the valve to the guide , which is now not large enough to allow the valve to slide thru.
Click to expand...

So is there any fix short of disassembly?
 
timwinters said:
Exactly, I could hear it click when I was turning the engine over...two clicks...then it started. Then rough running for about 15 seconds then it 'unstuck".

Like I said in my OP, it's done this about three times in its life...all three in the last 300 hours or so and in each case it has "unstuck" very quickly...in less than 30 seconds. So it's hard to diagnose.
Click to expand...

Do a cold compression check, you'll find it.
Have the cylinder overhauled now, prior to the piston striking the open valve. That will get you a whole new cylinder.
 
While your valve is stuck, you are spalling your lifter and cam shaft. The rope trick is not hard. The crap that the ream takes out is hard and will not go away with solvent.
 
I have done the rope trick (O-300) in order to get from A to M(mx base); it will do that but it is a temporary fix, eventually you will have to address that exhaust valve/guide.

PS see how it shakes at idle? At full power, you will think the airplane is going to come apart. At night, you might think you are going to die. [you won't, but it will scare the crap out of you] (btdt)
 
What's "the rope trick"?


Sent from my iPhone using Tapatalk
 
fill the cylinder with a flexible 3/8" cotton rope with the piston at bdc
raise the piston and it will push on the rope, which will push on the stuck valve.
'bonggg' and the valve is no longer stuck.
 
Let'sgoflying! said:
fill the cylinder with a flexible 3/8" cotton rope with the piston at bdc
raise the piston and it will push on the rope, which will push on the stuck valve.
'bonggg' and the valve is no longer stuck.
Click to expand...

That's not all there is to it.

the rope holds the valve closed while you shrink the valve springs to remove the keepers. Then you'll tie a string to the valve stem, lower the piston, remove the rope, and allow the valve drop into the cylinder, getting it out of the way to ream the guide. When that's completed, you can pull the valve back into place, re-install the rope to hole the valve while you re-attach the springs and keepers.

The rope trick enables you to ream the guide with out removing the cylinder and finding all the other things wrong with it.
 
Unsticking with the rope trick and nothing else done, it will likely stick again on startup. The real trick is unsticking and dropping the valve into the cylinder and pulling the stem out the spark plug hole to clean it and reaming the valve guide then reassembling.


Jim R
Collierville, TN

N7155H--1946 Piper J-3 Cub
N3368K--1946 Globe GC-1B Swift
N4WJ--1994 Van's RV-4
 
N3368K said:
The real trick is unsticking and dropping the valve into the cylinder and pulling the stem out the spark plug hole to clean it and reaming the valve guide then reassembling.
Click to expand...

That's how a mechanic on Long Island fixed the valve that stuck on the O-360 in my Tiger.

Had run rough on startup on a cold December morning in CT. Chalked it up to a FL plane not being used to cold temps.

Over Long Island Sound at 6,000' it began shaking and "backfiring" like crazy. Declared an emergency and circled down over a Long Island airport and landed.

Found this:

12410663983_b239e8e71b_o.jpg


In short, if there's any sign of a valve sticking the Most Conservative Action would be to get it fixed ASAP. It could lead to much larger problems in short order - or even injury or death depending on when and where it finally seized.

Anyway, not to be taken lightly or shrugged off.
 
timwinters said:
Every time I fly it's a hard lean run! I flew 5.5 yesterday @ 23 squared burning 10.2/hr.
Click to expand...

I forgot to ask, how many hours on these cylinders?
At the last overhaul were they new or rebuilt or?
 
The O-470 is kinda known for needing top end work from time to time. The rope trick may buy you some time, but you're eventually going to have to pull the jug and fix whatever is really causing the problem.

The OWT around the field is that this happens worse on these airplanes because they weren't designed to run on 100LL but I've never seen anyone have the crud that builds up analyzed to see what it's made up of. Maybe one of the assembled smarter mechanics can tackle that question.

Ours has had two jugs off of it in its lifetime. I don't know why people freak out and refuse to pull them and have a look and do the rope trick instead. Takes more mechanic hours ($) but that's pretty cheap insurance when you're flying behind a single mill.

My engineer brain says there's bolts on the silly things and they're on the outside where you can get to them, for a reason.

Sorry it's starting to happen on yours. I *imagine* it's happening on mine every time I get a start that doesn't seem "perfect", 'cause I know it *will* happen. I taxi around leaned to the point of nearly stalling and try to do all the "right" things, but it's an O-470, and eventually it'll need another jug pulled to look at something.

Heh. Just how it goes with this engine. They're simple beasts from a by-gone era where if it was misbehaving you got out the wrench and looked inside to see why. :)
 
FastEddieB said:
That's how a mechanic on Long Island fixed the valve that stuck on the O-360 in my Tiger.

Had run rough on startup on a cold December morning in CT. Chalked it up to a FL plane not being used to cold temps.

Over Long Island Sound at 6,000' it began shaking and "backfiring" like crazy. Declared an emergency and circled down over a Long Island airport and landed.

Found this:

12410663983_b239e8e71b_o.jpg


In short, if there's any sign of a valve sticking the Most Conservative Action would be to get it fixed ASAP. It could lead to much larger problems in short order - or even injury or death depending on when and where it finally seized.

Anyway, not to be taken lightly or shrugged off.
Click to expand...

Oh yeah, that brings back memories :yikes:

I had a similar thing happen on a single engine night cross country, long and short it caused the engine to no longer be able to make enough power to maintain altitude, glided to a nearby uncontrolled airport with really bad lights, brought her in high and slipped her down, uneventful. The airplane sounded sick enough someone who heard us. called the FD.


+10000 --> Get it fixed before you go anywhere, also get a good analyzer if you don't have one already.
 
Tom-D said:
I forgot to ask, how many hours on these cylinders?
At the last overhaul were they new or rebuilt or?
Click to expand...

The cylinders are original to the airplane. 1958 models. Third run. 3367 TT, 1249 hours since last OH. Chromed at last OH. The entire engine is original to the plane and I plan to keep it that way as long as possible. My cylinder guy tells me the cylinders have one more run in them.

FastEddieB said:
In short, if there's any sign of a valve sticking the Most Conservative Action would be to get it fixed ASAP.
Click to expand...

I agree completely but, when it only sticks for 15 seconds and then unsticks, it's impossible to tell which valve is the issue. Both of the last times a valve stuck, those times also for about 15 seconds each, we did a compression test both hot and cold and all checked out okay. :dunno:

denverpilot said:
The O-470 is kinda known for needing top end work from time to time.
Click to expand...

Agree...if they're not regularly flown. However, mine has been.

But, again, the main issue is determining which valve is sticking. Can't do the rope trick or OH a cylinder when one doesn't know which one it is and I seriously doubt a compression test will tell me (though I have one scheduled for Tuesday).

But again, we're straying far afield from my original question.
 
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The O-470 is kinda known for needing top end work from time to time.
Click to expand...

470s are prone to have worn valve guides and sometimes with that you get leaky exhaust valves. It's quite unusual to hear of "morning sickness" in a Continental. Unusual enough that I'd question whether it's really a sticking valve. Maybe a failing lifter?
 
Stewartb said:
470s are prone to have worn valve guides and sometimes with that you get leaky exhaust valves. It's quite unusual to hear of "morning sickness" in a Continental. Unusual enough that I'd question whether it's really a sticking valve. Maybe a failing lifter?
Click to expand...

Oh, it's a sticking valve.

My first suspect is the auto gas I burn (typical blend is 75% MoGas, 25% 100LL) We had to overhaul one cylinder a couple of years ago due to a worn valve guide, leaky valve, as you describe and I was amazed at the amount of auto gas varnish that was built up on all the various components. That can't be good for keeping valves unstuck.
 
timwinters said:
The cylinders are original to the airplane. 1958 models. Third run. 3367 TT, 1249 hours since last OH. Chromed at last OH. ]
Click to expand...

IOWs your telling me, they are due to start cracking at any time.

IMHO Chrome Cylinders are junk to start with. It was a repair procedure when we couldn't get new cylinders.

You never find morning sickness by doing a hot compression check. Make the aircraft safe to hand prop. Prior to the first start of the day pull the engine thru, one morning you will find a cylinder that has no compression.
Call your mechanic when that happens.

If this is nor repaired, and you continue to fly it, one day this will happen. The valve will be stuck open, when you start the engine, as you crank the piston will strike the open valve, this will bend the valve stem, as you continue to crank the engine will start and trash that cylinder which in turn will shed enough metal, including the chrome from the cylinder wall to ruin the crank.
At the 3rd overhaul I will guarantee the crank is too small to be re-ground enough to get the grooves out, so you get to buy a different crank, then you get to spend the money that you should have when the cylinders were chromed.
 
Stewartb said:
Did you say what kind of oil you use? Camguard?
Click to expand...

Cam guard does nothing for sticking valves.

My 182 customer has faithfully used it since he had his engine overhauled 4 years ago. he has replaced 2 cylinders for sticking valves. It does help the cam lobe to lifter life. as it was meant to.
 
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