EGT Drop - or increase - on one side of engine only... Anybody else experience this?

[SJ]

So, I'm heading out to Johnson Creek today in the C-180. The engine is pretty new, under 300 hours. Runs like a clock. While I am flying along at 8500ft getting close to flying over Yellowstone and other less friendly terrain than the giant flat runway I have been flying over for the last 500 miles, I notice that my oil temp has been creeping up a bit. Not really high, 188 or so, but a little high for cruise. I turn the money knob in a crank to give a little cooling and go back to staring out the window. Then I look down at the EI UGB 16 and see that cylinders 2, 4, and 6 are all 100 degrees lower than 1, 3, 5. I have the UGB "normalized" so it makes a nice flat line when things are going along fine. Well, the flat line went away. Engine still running like a top. EI of course is closed, so no help there.

So I called Steve Pierce, the guy who built the engine, and the only thing that we can come up with is an intake leak on one side. Only problem with that theory is that the O470 has a circular intake system, it is not branched. Oh BTW, the CHT's are PERFECT. Within 25 degrees of each other or less - this is a carburatored PPonk engine. Now, I have to admit that while I THINK that the EGT's on 2,4,6 dropped, it could be that the 1,3,5 EGT's went up.

I did a test flight before decided to RON in Riverton, WY this evening, with a plan to pull the cowl tomorrow and look at all the intake and exhaust stuff.

Even though everything was working perfectly, the little voice told me to check it out further (no it was NOT Laura's voice, although she was in agreement).

Any ideas folks?

sj

[SJ]

Sounds like maybe nothing to worry about

http://www.avweb.com/news/maint/egt_..._198791-1.html

Maybe I just need to "renormalize"... Nah, I still wonder...

[RaisedByWolves]

Can't hurt to take a look under the cowl. Could be something stupid/simple.

[sierra bravo]

Loose intake rubbers would be my first instinct. Not necessarily easy to find. Especially the first one at the Y. If its marginal it can work fine until the engine compartment gets warmed up and then get leaky. Watch you MP and see if it wanders from your settings. Another sign.

Do you have thumb-turn worm clamps? Take a 1/4 or 5/16 nut driver and use a cutoff wheel tocut a groove on the centerline through both sides of the socket head and wide enough to slip on and capture the thumb turn. It make a great tool for tightening those clamps and you can get more torque on them than when bumbling around with pliers. You can do the same thing with a socket.

[benflyn]

Mag check ok?

[SJ]

Thanks, SB. Those intake rubbers seemed like the only logical explanation to me - even though they are only a couple hundred hours old. I was thinking one is probably loose also, but you can only see a couple of them through the cowl doors so I will pull the cowl this morning. Good idea on the socket. The MP was steady, and there were no mag problems at all. No unusual sounds, anything other than the oil temp also creeping up a bit more, but that was manageable with fuel / cowl flaps. I'm an agressive leaner in cruise, but fuel flows were right where they always are (actual, not vacuum based) so I was not doing anything different than usual.

i will report back later.

Thanks

sj

[Steve Pierce]

All I can come up with is a UBG16 problem.I would think that the CHTs would up if there was an intake leak. Can't explain why one side would go up or down. I think it is probably a good idea to un-cowl and look it all over though.

[SJ]

Steve, All my experiences (except for fuel flow transducers) with EI and other things like this failures have been yes/no type. This is only 100 degrees per cylinder, all cylinders are on the same side, I don't think this is an electronic failure. If it was one cylinder, or all three went dead, ok, then I would be thinking the gauge/probe. Electronic stuff is pretty predictable in the way it fails, this does not seem like that to me.

Stay tuned!

sj

[Steve Pierce]

I agree until I got a call at 6 am on the morning my folks were departing Graham. My Dad's clipper had low oil pressure as indicated by his EI oil pressure gauge. Cleaned the oil pressure relief valve and put it all back together and still low pressure. Put a mechanical gauge on and it was normal. He flew home and it went back and forth. he checked all connections and discussed with EI and it works perfectly now. Never did figure it out.

[ag-pilot]

Steve check to make sure the Balance Tube across the fromt of the engine has tight clamps and something didn't rub a hole in it.. Had that happen on a Ag-Truck once and it ran fine but had weird quirks,,, Cowling wore a hole in it. If its not the gauge its induction somewhere. Look for dark fuel stains all around the induction tubes and hoses

Dave

[SJ]

So far no smoking gun. I will check that tube next. The ercoupe in the corner should bring me good luck.

Sent from my ADR6300 using Tapatalk 2

[Patrol Guy]

Should have taken the super cub to a super cub fly-in???

[aktango58]

check your baffle seals...

all on same side... bit hotter, sounds like you are not getting the cooling you were before. As the cooling goes down the oil gets warmer as will all else....

(just a pilot thought)

[SJ]

Found a number of the sleeve clamps to need a full turn of tightening. Test flight shows the did worked, but will conffirm after it heats up enroute to JC. This is a great place and I greatly appreciate the help from Jims Aircraft!



Sent from my ADR6300 using Tapatalk 2

[fobjob]

Burned up a cylinder in my 182 from a crack in the intake balance tube that was invisible due to it being along the weld of one of the brackets holding on the balance tube, since they are welded, behind the balance tube....where you can't see it without contortions...

[aktango58]

if you have the engine running and spray starter fluid on intakes, the engine will change rpms when the ether is sucked inside...

[Jim 4WF]

Use a clean vacuum cleaner to blow air in the carb heat hose with carb heat on. When you spray the intake with a soap and water you will be shocked on how many leaks there are. I almost always find leaks on continental intakes or cylinder gaskets. We should be doing this to exhaust systems so it dosen't take much more to make sure there is a tight intake.

jim

[RAC cubs]

carb ice my 180 was a carb ice king,it forms in strange ways no rime or reason,could have formed more on one side of carb or in take causing uneven flow.

[slowmover]

So Steve does this experience make you more of a believer in a digital engine monitor? I'm tempted to put one in but I've had 2 A&Ps tell me they aren't worth the money in an O-470 like I'm running.

[mike mcs repair]

soft or broke or hanging open intake valve spring on that side(or other??)..... kills off the 'suck' in that part of intake.......

to test... pull valve covers, make sure piston is NOT at top on cyl being checked, hit each valve rocker with plastic hammer to open and close valve, LISTEN to sound, you will hear a very different sound on a broken or soft spring cylinder.....

[SJ]

Hey Folks! Thanks for all the suggestions. It is still doing it, but less so. I have an annual inspection coming up in a couple years and am going to dig into more thoroughly then. Other than the strange monitor readings, the plane ran like a sewing machine (only much, much, louder).

I would have love to have my Super Cub at Johnson Creek this weekend, but if that had been the only option, I would not have been able to go - I just did not have the additional time (and stamina) to fly it 1000NM this year.

Thanks again. Stay tuned for what we find out...

sj

[12Geezer2]

Wait till you get to be my age. Just completed a 1600 mile journey in a PA-11. My "backside" may NEVER recover--geezer Dan

[mike mcs repair]

muffler cone broke out of one side allowing it to breath easier?(untill it lodges in tail pipe opening restricting it..)

[sierra bravo]

Has the engine's start-up personality changed? Have you tried adding partial carb heat to observe the effect on CHTs in flight?

Tightening clamps is a good thing but its still possible to have some displacement where the rubbers overlap the tubes. In my own case it was at the right branch of the induction Y above the carb. Definitely the hardest one to inspect and the displacement had gone undetected by myself AND a very good mechanic before, because a local carb specialist insisted we check, double check, and check again, MCS Mike found the culprit.

[SJ]

With the symptoms of all on one side, I gave those four sleeves (on each side) off the Y the most attention, but they are very hard to access as you point out. I think taking them off and putting them on is a good idea.

It is running perfectly otherwise. No change whatsoever in behavior. It is interesting that it is not until say 8 - 10 minutes into the flight that it starts to do this, like it is something warming up and letting air in maybe.

sj

[Cub Builder]

The most common issue is with the crossover tube, which you guys have already checked. I ran into this recently helping a friend troubleshoot his 182 that ran the temps imbalanced on one side, but at a low idle, all three cylinders on one side would stop firing and go stone cold. It idled very nicely on 3 cylinders, then would pick up the other three as soon as the throttle was advanced slightly. What we eventually found was a cable that had rubbed a significant hole into the intake tube off to one side of the splitter just above the carb. It was not at all obvious as the cable kept the hole hidden, but the effect was all three cylinders on one side running differently from the three on the other side.

-CubBuilder

[SJ]

Ok folks, when I was flying back from JC the other day I texted Steve Pierce with the thought that it might be muffler related. He said I should have a look up the tubes and see what I saw. Preliminary report is that one looks quite different than the other one. I had loaned my (cheapo) Borescope out and will get it back to have a better look shortly. Hopefully, a quick trip to Dawley for the muffler will solve this mystery.

sj