Sticking Exhaust Valve - Diagnosis and Fix!

[skylor]

Originally Posted by Jpm757

The only "Lycoming" approved additive is LW-16702 Anti scuffing agent. It adds about $35 to the cost of an oil change. However there are several "FAA" approved additives such as Avblend,

The Aeroshell Plus grades (i.e. W100+) contain LW-16702 so you don't have to buy a bottle of additive separately.

Skylor
RV-8

[Frank Jackson]

I should have looked at this sooner. Yesterday the #2 exhaust valve on my Lycoming IO360 stuck completely and bent the pushrod. Fortunately I was in the pattern at a nearby airport and immediately landed. It's now at the FBO at the same field getting a rebuilt cylinder. It had been running rough at idle and low power settings but smoothed out at runup power and higher. The engine had only 380 hours on it. I'll be doing a wobble test on the other cylinders.

[scrollF4]

Originally Posted by Frank Jackson

I should have looked at this sooner. Yesterday the #2 exhaust valve on my Lycoming IO360 stuck completely and bent the pushrod. Fortunately I was in the pattern at a nearby airport and immediately landed. It's now at the FBO at the same field getting a rebuilt cylinder. It had been running rough at idle and low power settings but smoothed out at runup power and higher. The engine had only 380 hours on it. I'll be doing a wobble test on the other cylinders.

Frank,
I'm like you. I never paid attention to this post until your write-up today, because it happened to me this week.

My factory-new-plus-400 tach hours IO-360-M1B suddenly got rough under 1350 RPM along with an associated total drop of EGT on cylinder #4. I immediately showed it to Randy Richmond (aka Monk, our local 52F totally awesome expert of everything RV). He ran a compression check (there was none....0 inches, with a loudly audible hiss from the exhaust pipe). Diagnosis: Stuck exhaust valve.

Apparently, many (most?) mechanics will simply tell you the jug must be removed and sent to some repair house somewhere. Also, apparently, few will take the trouble to work the problem on-engine, if it can be properly worked on-engine. Randy actually conducted something akin to endoscopic surgery to clean the valve and inspect the pushrod.

All is Code 1, no bends, compression is good, and a cleaner valve. Of course, if the bits and pieces showed anything beyond mere carbon (or other gunk) buildup causing the stuck valve, he'd have elevated the level of repair.

I can't thank Randy "Monk" Richmond and Richmond Aviation enough. KELLI GIRL flies again!

[bullojm1]

Over the last few flights I noticed the #1 exhaust valve might be sticking. When the engine was warming up, it ran rough under 1,000 RPM and the CHT and EGT were low on #1 (CHT was 150 where others were 200+, EGT was 700 where others were in the 900's). As soon as I increased the throttle past 1,000 RPM, CHT and EGT increased to their normal places.

The timing of this was fantastic, as I was just starting the conditional inspection.

Yup, definitely a stuck #1 exhaust valve. If you're wondering about the bracket I have installed on the cylinder, it's what I used to pivot my home-made valve compressor on (see http://www.vansairforce.com/communit...2&postcount=59).


1/2 way through reaming out the guide, I took a pic with my borescope of what the inside of a guide looks like that's gunked up.


And after! Like night and day.



The only thing I changed from my original write-up (besides my new and improved valve compressor) was my method of keeping the exhaust valve seating for installation. Originally I used the "Rope Trick". One thing pointed out to me was there is a small chance of the rope forming a knot inside the jug, and then you have to yank it to get it out. So this time I tried using compressed air, delivered through the differential compression tester. I rotated the prop until the #1 piston was at the bottom of its stroke and the intake valve was closed. 60 psi of pressure seemed to be the right amount to keep the exhaust valve forced tight enough against the seat to install the springs.



All back together and ready for the next adventure! The whole process took me a little over an hour, including dropping and reinstalling the exhaust.

[RV7 To Go]

I think this is a great reference thread on something that seems to come up regularly. Any chance of the moderator making it a Sticky in this category or maybe in the Traditional Engines section?
Al

[painless]

So Mike, inquiring minds want to know......

How come your guides are getting gunked up?? This is the second jug to have the problem for you, correct?

[cujet]

As DOM for a small fleet, we see this issue from time to time.

A couple of notes:

After reaming the guide and cleaning the valve's stem, it's possible to (very sparingly) use valve grinding compound along with a rubber hose on the valve stem hooked to a battery drill to very slowly, carefully and intermittently (I know you guys understand this) clean off the valve face and seat via an "in place lapping" . Apply a tiny quantity of valve grinding compound (half a drop) through the exhaust port with a Q-Tip. Cleaning up afterwards takes some time, but it's possible to correctly ensure no valve grinding compound remains.

The reason to do this has to do with heat transfer. The valve will remain slightly cooler if it has a good heat path at the valve seat area. Leading to fewer problems with valve sticking.

Aeroshell 15W-50 use seems to result in fewer events. In fact, the only time we've experienced it (not so for others) is with an oil other than AS 15W-50.

Also, a very lean taxi seems to help.

[tx_jayhawk]

Does anyone know if that reamer size mike ordered is the same for all lycomings? Angle valve and parallel valve?

[krw5927]

Originally Posted by tx_jayhawk

Does anyone know if that reamer size mike ordered is the same for all lycomings? Angle valve and parallel valve?

According to Lycoming SSP-1776, the parallel valve and angle valve direct drive engines have very slightly different exhaust valve guide diameters:

https://www.lycoming.com/sites/defau...20Complete.pdf

[stevengrasley]

I had this same experience at the 600 hour mark on my Lyc O-360-A1A. That was 4 years and 800 hours ago. I was at 13,000 feet above Columbia, SC on an IFR to Charlotte when JAX Center gave me a descent to 11,000. I looked at the panel when the altimeter crossed 12,000 and the engine got the shakes. Instinctively pushed the mixture, hit the fuel pump, switched the tank, rev?ed up and down and no change. Noticed #4 EGT & CHT plummeting. I told ATC that I needed to land in Columbia as I lost #4 cylinder. JAX Center told me he had declared an emergency for me and gave me to Columbia Approach as they were expecting me.

Although the engine was running rough I still was easily flying at 142 KTAS at 2250 RPM which was the most comfortable setting. Crossed the threshold at 100 knots as wanted to keep the engine running if possible at low RPM and flew it down to the ground. Thankfully I think there is 10,000 feet of runway at Columbia International. Taxied to FBO and shut down with a loud backfire and some black smoke. Pulled back the canopy and the good ole boy at the FBO said, ?That don?t sound too good.? The emergency vehicles were all on the runway when I landed and drove up to make sure I was OK. I was but I can?t type what I said in the next few minutes.

Based on what was going on Eagle Aviation (GREAT PEOPLE!!) got me a hangar as it was clear I would be here for a while. I was introduced to a number of great locals that were more than willing to help. There were quite a few Team RV members in the area, some EAA national board members at KCUB, and a ton of RV builders there too. After describing what happened they all shrugged their shoulders and said, ?Stuck exhaust valve. Here?s what you need...? I learned this entire method from the very beginning of this post on the fly in real time. Thankfully airplane engines are essentially highly glorified lawn mower engines so I pulled it off after driving to Charlotte for 3 days of business meetings.

The gang at KCUB leant me everything I needed with the exception of a reamer. I had valve compression tools of two types and a wobble tester etc. Everything else I had was in my flying tool kit. Yes...I now have everything I need in my flying tool kit to do this job easily in the field, but I don?t carry the wobble tester. The old timers all told me to use a piece of bent welding rod or coat hangar wire and a piece of red 3M pad in a drill since nobody had the right reamer. In a pinch it worked.

In my case the valve seized and bent the push rod and tube. Thankfully there was a parts shop on field and in two days I had push rod, push tube, exhaust gaskets, and tube seal O-rings. Grand total parts was $136. During the entire descent all I could imagine was how much this was going to cost because I was not sure what happened until I pulled the cowl. I was stunned how cheap I got away with on this one.

Took the better part of a day to do the job as I was learning on the fly. Proper spring compression tools are a must but are small and simple when you get the right ones. The bar that Spruce sells is my favorite. Simply put the valve guide was gunked up bad. I had a rough start a few weeks before this event and looking back on it I should have known. I also wish I had been up to speed with the Lyc SB that outlines this whole condition.

I finished the repair and got the engine buttoned up and did a short test flight. All good. Flew home 600 nmi the next day. I bought the proper reamer and then did all 4 exhaust valves. I found #1 a little dirty, #2 was tight, #3 was nothing (funny that one is always the hottest), and #4 got a proper cleaning when I did the reamer. I did all 4 in a morning. The rope trick is fine but 60 psi of compressed air is better.

After talking to a lot of old timers and a Lyc employee at Sun N Fun who would not admit he told me so, all suggested that using Marvel Mystery Oil at 4 oz per 10 gallons of gas and occasionally substituting one quart in the engine oil 1-2 times per year would eliminate this from ever happening again. So that?s what I have been doing. Based on the Lyc SB I thought another check at just over 1,000 hours would be a good idea. I did. Everything clean as a whistle and wobble test was great. I?m nearly at 1,500 hours now and no sign of any issues at all. Since my incident I have flown nothing but AeroShell 15W-50 with Camguard.

I would have rather not had this experience but am a lot smarter for it. Hope my story might help somebody else one day.

To the chap that wrote this original post: Bravo! I wish I had found it when I was in need. I just read it today for the first time. Excellent post and pics. Well done my friend.