Cylinder Low Comp/ Oil Consumption

And to be clear, a valve issue would not cause loss of oil? So my issues are likely at least partially rings and partly valves (based on hearing the leak into the exhaust manifold)?
 
And Tom you are right, this engine runs smooth as silk, it is just a bit of a dog right now!
 
Danny Dub said:
And to be clear, a valve issue would not cause loss of oil?

Badly worn valve guides can cause high oil consumption.

So my issues are likely at least partially rings and partly valves (based on hearing the leak into the exhaust manifold)?
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Pull the cylinder, it is apparent that you have piston and ring problems also, pull it, and let us see what comes out.
OBTW I have two brand new superior piston and ring sets you can have cheap.
 
Danny Dub said:
Fill the jug completely? Seems like it would leak past the rings and end up in the oil. I am all in on trying this procedure just want to understand. I'm guessing you drain it from the lower plug the next day? What would be the remedy if the MMO leaked into the crank case?

Thanks guys for all the comments.
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No, not remotely completely. Put your finger or thumb over the plug hole until you feel air being pushed out on the compression stroke, then bring the piston up so it's about an inch or so from the top. Fill with MMO. The carbon softening is done by the solvent when you rock it GENTLY into the piston rings and leave it to soak. You're not looking to hydro-lock the piston, just push stuff down into the rings. If the piston easily turns without the solvent being held by the valves then you have one heck of a valve leak, and that too is valuable negative information.

Yes, you drain it by removing the bottom plug. A couple ounces of MMO won't hurt anything in the crankcase. Some folks add it to oil and/or fuel as a routine measure, though it's not an approved additive.
 
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A broken ring, worn valve guide, scored cylinder wall, ring gaps lined up, will all cause higher than normal oil consumption.

also a broken/cracked land, scored piston, and stuck rings.
 
To use a qt. an hour would be one hell of a worn valve guide. Just sayin'.
 
I don't understand, as an owner, why a 20/80 cylinder coupled with high oil consumption and demonstrated leakage is just not pulled and replaced. When it is off, dollars to doughnuts you are going to find one or more obvious issues that will make you glad you repaired or replaced it. It's not likely lined up ring gaps...that is rather wishful thinking that may get you hurt.
 
Well, there's another non-invasive test that might give you a clue as to what's going on. Lay hands on a digital manometer, you can find one pretty cheap online, or maybe at a plumbing supply shop that sells gas accessories. Rig up a cork with a tube passing through that you can safety into the oil fill. Warm up the engine, then run it up and see if the case is being pressurized beyond spec. Lyc's are between 1" and 2" wc. (water column). Don't know what Conti's are, but I'm sure there's a spec and I bet it's probably pretty close to the Lyc. . If the case isn't being pressurized way beyond spec. the problem isn't the rings, piston, cylinder wall.
 
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I'm surprised nobody has asked what the compressions are for the rest of the cylinders. If they're all rather low too (50-60?) it's a sign that the engine is worn out, and replacing one cylinder is a waste of time and money.

A quart an hour going though one cylinder should completely foul the plugs and stop all firing there. I suspect that the rest of the cylinders are also using lots of oil.
 
chemgeek said:
I don't understand, as an owner, why a 20/80 cylinder coupled with high oil consumption and demonstrated leakage is just not pulled and replaced. When it is off, dollars to doughnuts you are going to find one or more obvious issues that will make you glad you repaired or replaced it. It's not likely lined up ring gaps...that is rather wishful thinking that may get you hurt.
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Just MHO as an owner, if a jug has to be pulled, it has to be pulled. But there is always the significant chance of a maintenance induced failure in doing so, so I want to be darn sure the jug has to be removed before it's pulled off an engine that's run well for 800 hours. If that means spending a little time exploring diagnostic options, so be it. From what I'm hearing from the OP, because his wrench is hearing air leaking into the exhaust, the problem is in the head/Valves, but coupled with the high oil consumption, probably goes beyond a guide or seat. But why not confirm if possible before turning a wrench?
 
Chip Sylverne said:
To use a qt. an hour would be one hell of a worn valve guide. Just sayin'.
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Yer right, one cylinder with bad guides won't do the symptoms here.
reading my statement in the context it was written. 6 cylinders with badly worn guides will add to high oil consumption.
 
Dan Thomas said:
I'm surprised nobody has asked what the compressions are for the rest of the cylinders. If they're all rather low too (50-60?) it's a sign that the engine is worn out, and replacing one cylinder is a waste of time and money.

A quart an hour going though one cylinder should completely foul the plugs and stop all firing there. I suspect that the rest of the cylinders are also using lots of oil.
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He did say one low compression, but didn't give numbers .
 
Chip Sylverne said:
Just MHO as an owner, if a jug has to be pulled, it has to be pulled. But there is always the significant chance of a maintenance induced failure in doing so, so I want to be darn sure the jug has to be removed before it's pulled off an engine that's run well for 800 hours. If that means spending a little time exploring diagnostic options, so be it. From what I'm hearing from the OP, because his wrench is hearing air leaking into the exhaust, the problem is in the head/Valves, but coupled with the high oil consumption, probably goes beyond a guide or seat. But why not confirm if possible before turning a wrench?
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The TCM 50 cubic inch cylinders all need attention at about a 1000 hours, this is pretty normal. the GO- runs a higher RPM and needs attention sooner than the 0-300/0-200
this may or may not apply here.
 
The other cylinders are in the high 60s for compression.

If the oil consumption is a valve guide problem, where would the oil go? Burned up or leaked in engine compartment or on the belly?
 
Danny Dub said:
The other cylinders are in the high 60s for compression.

If the oil consumption is a valve guide problem, where would the oil go? Burned up or leaked in engine compartment or on the belly?
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When your GO-0300-D has 800 hours and all cylinders are in the 60s Has high oil consumption. It is time for 6 new cylinders. This is so typical of the GO- it's pitiful. sorry.

Does your engine smoke? it would if your guides were bad enough to do a qt per hour.
Guides will add to oil consumption but not to the extent of 1 qt per hour.
 
Danny Dub said:
The other cylinders are in the high 60s for compression.

If the oil consumption is a valve guide problem, where would the oil go? Burned up or leaked in engine compartment or on the belly?
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Generally leaky guides make themselves known by leaking oil into the cylinder when the engine isn't running, and creating great clouds of smoke just after starting. But in answer to your question, the path for leaky guides is into the combustion chamber, not onto the belly.
 
Chip Sylverne said:
Generally leaky guides make themselves known by leaking oil into the cylinder when the engine isn't running, and creating great clouds of smoke just after starting. But in answer to your question, the path for leaky guides is into the combustion chamber, not onto the belly.
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If the engine isn't running the oil will simply drip into the exhaust or intake. there is no airflow to carry the oil into the combustion chamber. but just as you say it will smoke like hell if when the oil gets into either manifold.
His GO-300-D has a cylinder that the guides are in the top of the cylinder head and the drain tubes in the bottom. the guides in his cylinder get oil from splash coming up the push rod to oil the rocker arm. that compartment will never flood and cause oil to set above the guide.
 
The leaky oil ....Tom. o_O

I've seen an intake valve badly oiled....due to worn guides. Compressions were in the high 70's and burning a quart every two to three hours.
 
Danny Dub said:
The other cylinders are in the high 60s for compression.
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That doesn't sound hunky-dory, and would explain the oil usage rate. You could be pumping oil from all cylinders. If I was burning 1 qt/hr and had compressions in the 60s and one cylinder in dire straits (20/80) I would be seriously considering if it was time for a top or major overhaul, painful as that may be. Your engine is trying to speak to you...I would be very surprised if you don't have wet bottom plugs. Engines will often run great and develop rated power with low compression, but the low compressions are a warning sign that all is not necessarily well, especially if they are not temporarily, but consistently low.
 
You guys are worrying me. A lot of these symptoms sound familiar. If the case was being over pressurized and pushing oil out the drain tube, what's the fix for that?

Just guessing: buckets.JPG :eek:
 
chemgeek said:
That doesn't sound hunky-dory, and would explain the oil usage rate. You could be pumping oil from all cylinders. If I was burning 1 qt/hr and had compressions in the 60s and one cylinder in dire straits (20/80) I would be seriously considering if it was time for a top or major overhaul, painful as that may be. Your engine is trying to speak to you...I would be very surprised if you don't have wet bottom plugs. Engines will often run great and develop rated power with low compression, but the low compressions are a warning sign that all is not necessarily well, especially if they are not temporarily, but consistently low.
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That's where I am.
Before I'd consider a top end, there are other things I'd want to know, gear box clearances, case seam leakage, timing gear back lash. IOWs how good is the lower end. The GO- s aren't known as long life engines.
 
Tom-D said:
That's where I am.
Before I'd consider a top end, there are other things I'd want to know, gear box clearances, case seam leakage, timing gear back lash. IOWs how good is the lower end. The GO- s aren't known as long life engines.
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Now the bad news, $22-$25k for the overhaul, if the gear box passes the backlash check.. OBTW I haven't seen one that would in 20 years.
 
Tom-D said:
That's where I am.
Before I'd consider a top end, there are other things I'd want to know, gear box clearances, case seam leakage, timing gear back lash. IOWs how good is the lower end. The GO- s aren't known as long life engines.
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I think a lot of that depends on how they're flown. They are a high rpm engine, and as such they like to be flown that way. I've known a couple guys who owned them, and flown by the book they do ok. They don't do well when flown like a direct drive. Pulling back the power and using the prop as a brake es no bueno.
 
Chip Sylverne said:
I think a lot of that depends on how they're flown. They are a high rpm engine, and as such they like to be flown that way. I've known a couple guys who owned them, and flown by the book they do ok. They don't do well when flown like a direct drive. Pulling back the power and using the prop as a brake es no bueno.
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That's the stuff you need to know before you make the decision.
 
The IO360-KB mod is the best solution. but the engine mount was 15k last I knew.
 
Lots of troubleshooting yet to be done before spending the big bucks. One thought ....

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Tom-D said:
Easier way..hold your hand over the oil filler neck, if you can feel and pressure it's too much
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Thanks Tom, are you talking about the oil filler tube with the dipstick in it (O-300)? With the engine running, that would be difficult to tell I would think.
 
iflyvfr said:
Thanks Tom, are you talking about the oil filler tube with the dipstick in it (O-300)? With the engine running, that would be difficult to tell I would think.
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both major engine brands carry very low pressure in the case. both have oil filler ports, placing your hand over that port you should feel no pressure.
 
Danny -

this was about 1.5 yrs ago - did you find the issue and what was it if you did -

I’m having a similar issue and in searching the internet ran across this thread -

thanks



Danny Dub said:
Hi gang as always thanks for any insight you can offer.

We have a Cessna 175 with the beloved GO-300 motor. At annual the number 1 cylinder is showing low compression (20) and we are using oil about a quart an hour.

Our AP suggests replace cylinder and that should fix both issues. My co-owner preferrs the option of working on the valves to try to bring the cylinder into specs.

I am not particularity mechanically knowledgeable and I'm sure the mechanic is giving his best advice but he doesn't really have the tooling to do the work.

I guess my question is does it seem likely that one low compression cylinder could create that much oil loss or do we likely have multiple issues? The bottom of the plane does not show much oil so I don't think it is just blowing out the breather tube.

Thanks!
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Sold the plane. I think the new owner did the right thing and did a top overhaul. Last I heard it is flying again.

Sent from my Pixel 3 using Tapatalk
 
LSK said:
Danny -

this was about 1.5 yrs ago - did you find the issue and what was it if you did -

I’m having a similar issue and in searching the internet ran across this thread -

thanks
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I recently had a similar issue with my Twin Bonanza. Left engine was suddenly consuming oil at a rate of >1qt/hr. Little bit of troubleshooting (mostly checking exhaust pipes) led to a bad #2 cylinder. When we pulled that cylinder, we found a broken compression ring. Replaced the cylinder, problem solved.
 
Salty said:
It’s the fact that you post so authoritatively on airplanes you’ve never even seen with few facts that is the problem. I don’t discount your knowledge, it’s your judgement that I just can’t trust based on your history. I’d bet you’re a great mechanic, just not so great at the internet thing.

I will grant you that this is different in that it’s burning oil, but that’s largely a subjective thing. To be so sure in the other thread that they should never pull the cylinder, but in this one you're sure they should. All based on a few lines of description by someone that may be totally naive to what they are saying for all you know.

Bottom line, I’ll admit my criticism was too harsh on this one. you seem, in general, to be very passionate but not very consistent to me, but a lot of that is because you don’t say things straight, you often hold back in the “whys” of your logic, and come across very wish-washy. To be clear, I think it’s your communication style that trips me up more than your mechanical knowledge.

There’s just something about your style that I can’t resist busting your chops. But I apologize on this one.
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Bell206 said:
I believe he also wanted to fly IFR, legally, to his annual shop in Nov. It's all in the OP.:rolleyes:
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Thanks for explaining and apologizing to Tom. I’ve met him and dealt with him personally and find him to be a really good guy that just doesn’t deserve the bashing he sometimes gets here.
 
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