EGT CHT High temps

WebMaster · #1 06-25-02, 09:10 PM

Was over at Meigs on Sunday, and on Monday we left. 69 337D, normally aspirated. When I started the engines, shortly there after, the rear engine EGT went up, close to where i run it at 50 rich of peak. Standard Cessna Gauge. No actual temps displayed.
Mag check was normal.
My initial impression, was that it sat out, overnight, humid lakefront enviroment, I got moisture in the gauges, or something.
Take off, slightly less MP than front, but that is normal. However, seemed to be less than normal. However, very High surface temp and humidity. Don't know how much of that was the cause.
EGT stayed where it was, throughout climb, and if I leaned it, it got higher, but at cruise, fuel flow was pretty much normal. We have Shadin Digital, and EGT settled in to what is normal.
Landed in Kalamazoo, dropped my wife off. During approach, EGT dropped down, in a fashion that I would call normal for approaches. A few minutes on the ground, headed to Grand Rapids, where I keep the plane. EGT showed the same as Meigs, high, and oil temps were up, both front and rear. Again, 90+ Outside air temp, and lots of humidity. Climb performance was same as coming off of Meigs. Slightly lower than "normal" MP. Level off, and everything gets to where it normally is.
Landed in Grand Rapids, and EGT stays up, slightly, and CHT stayed up a lot.
Took the rear engine covers off, today, and looked. On the rear engine, there are little exhaust pipes that connect to a collector. There are little clamp sort of things that make the connection. The collector goes to another clamp thing, that is spring loaded, and thence to the muffler. On the right side of the engine, where the single EGT sensor is, there is evidence of escaped exhaust gases, yellow stuff, at each connection of the pipes.
There are, to my feeble mind, 2 potential causes.
1. Somehow, I am running very much lean, especially on the right side. (fuel flow does not bear that out, because if anything, I was running at tad bit rich on the rear).
2. I have leaky exhaust, which is causing the EGT sensor to malfunction. It appears that the cht sensor is also on the right side, so if I have leaky exhaust, that is why CHT was high when I landed.
Your thoughts?
What is the fix?

Thanks as always.

WebMaster · #2 06-25-02, 09:13 PM

I notice the escaped exhaust gas thing only on the right side. Left side is normal. Dark Pipes. Right side pipes have yellow sort of deposits near all pipe connections.

SkyKing · #3 06-26-02, 12:19 AM

Larry,

You didn't say, or interpolate for us, where the CHT temps were, but assuming they were below 400 degrees and in the green, not much to worry about.... when you get these hot ambient air temps, you're going to get slightly hotter engine conditions. Since you haven't had the airplane THAT long and most likely haven't been through a "HOT" summer, you're probably experiencing anxiety at the increases.

Exhaust leaks will normally appear as whitish whisps... not sure about "yellow", but maybe you should have you mek-a-nick check that the exhaust nuts on the flanges are torqued up properly.

If you're REAL concerned that you've got an exhaust leal, what you can do is hook up a shop-vac and use the 'blower' end -- make sure the filter and the canister are CLEAN before you begin -- so you won't blow any debri into the engine - and then fashion a connection of the hose to the exhaust pipe outlet using duct tape and pressurize the system. Apply some kids 'bubbles' solution or soap suds around the flange connections and over the pipes and watch... bubbles forming are okay, but if the bubbles blow away... then your mek-a-nick needs to do some tightening or look into matters further for cracked pipes, etc.

Not sure how the normally aspirated versions are, but on the turbo P-models, the riser from the exhaust pipes connect using a spring thingee with two nuts on each side...sometimes we've seen these items develop a small crack and start a small leak... sometimes you can reverse these end for end as long as they're not cracked all the way through and get a bit more mileage out of them. Since the manner in which they connect -- they wrap around the outside of the riser -- there's no possibility of anything getting into the exhaust stream and into the turbo... but, alas, I digress too much as you probably have a different set-up on yours.

Probably just the HOT WX!

SkyKing

GMAs · #4 06-26-02, 02:00 AM

Hmmmm... well their are a couple of things that could have done this for you... one is the fuel pump low pressure diaphram... here the un-metered pressure is going to drop down a little... and cause you to lean out a bit... but, looking real close at the fuel flow/pressure guage you should have seen a change... another item is a plugged injector on the side... that was runing lean... and while you said that the spark/mags were checking out ok... you could have had a plug that was fouled...out in flight... but, the fact that the egt is reading high... and the oil temp is high indicates that your running lean... on that side.... or both... first to check the fuel system... check the gas corolator... and make sure its not leaking .... air in... not fuel out... when was the last time it was serviced... you might want to use a new set of o rings and clean it and check it out at the same time... first... as any air leaking into it... is going to make the engine run lean... its located in the wheel well and it is/has been a source of the rear engine runing hot... if it leaks air in... while its good enough to keep the fuel from coming out... look for the tale tale gas stain.... on the top where the pull rod goes in and around the body where the cup goes up into the housing...

what to check.. check for gaskets leaking at the intake.. check for the rubber connection hoses to be leaking... air in... check for cracks around the intake pipes... check for leaking spider tubes and their fittings from the top fuel distrubutor... and then remove the injectors and clean them... thats about as far as you can go... without them mechanic doing the next items... on the fuel system... to check...

now for the bad news... it could have been a valve hanging up... and you were leaning out the mix especially if it were a intake valve.. that was sticking... and a person who can test to that is Skyking... he knows what you should put in the oil to get them un-stuck... but, its not a avation product so I can't recomend it... smile... you didn't mention what type of oil your runing... but, anything less than aeroshell 100w is not good... at them temps... if its a valve... you can do a comprssion check... or pull the engine thru and you should feel the cyc that is leaking or the valve is sticking open... probably a intake... if it is...

Ok... let us know what you find out... G.M>

WebMaster · #5 06-29-02, 11:15 AM

It's been a busy week, and this is the first chance I've had to visit the plane. Mom's decided it's time to head West, hence the quick trip from Meigs.
I took the power head from the shop vac, and hung it from the prop, and plugged the tube into the exhaust. Those engineers are amazing, it plugs right on, they must have been talking when they decided to size the tube on the shop vac. Anyway, the exhaust joints look like a lawrence welk show. Especially on the right side, where I had noted the discoloration. Looked in the shop manuals and the CHT probe is right above the most offending leak. Hence, high CHT??
Tried the input system, no leaks, but the air filter looks like an oily mess. But, wouldn't that cause it to run rich, not lean? Arrgh, just thought about this, and the throttles are closed, i'll have to try it again.
Looked for the gascolator, strainer, thingie, and can't find it, and it's beyond what I can do anyway. I'm trying to accurately diagnose this, since it has to go to the high price, less competent FBO. The friendly fbo has closed it's doors. My major concern with these folks (the high priceone) is that they have a way about them. They have steadfastly not checked hydraulic fluid. When my squat switch didn't work, the first response was jack it up, put the mule on it. I explained that the gear wouldn't go up, and the hobbs quit, at the same time, so it's obviously in the squat switch circuit. Anyway, I like tinkering. It's an engineer thing.
Oh, turned the prop over by hand, and the only noise was from the impulse coupling. So, I believe it is not a stuck valve.

WebMaster · #6 06-29-02, 12:49 PM

I opened up the throttle, and checked intake manifold for leaks, and there are none.
Also, all the little nuts on the exhaust stuff are tight.
Any thoughts?
It's time for the techamechs to look, but not today, obviously, and I'll have to see how busy they are next week.

GMAs · #7 06-29-02, 04:16 PM

Ya but, did youlook at the hoses for leaks... and other things... next step is to do a compression check... if you can't determine which one is leaking...

Kevin McDole · #8 06-29-02, 07:01 PM

Larry,

After a shop visit once I had high EGT & CHT's. To make a long story short, the mag timing had been set incorrectly. Fixing that solved the problem.

GMAs · #9 06-29-02, 09:50 PM

larry said that he didn't have a mag drop... and both mags set wrong.. well it could happen but,,,, it seems strange that one is trucking along and then suddenly after over night stay he starts runing a higher EGT... could be maybe one came lose... but, again the probability of that is real slim....

After checking for leaks... on the one side he said he thought was runing hotter... we need to do a compression check... as I will bet the reason that his mP and all isn't comeing up is because he either has a burn valve... or a intake that is sticking a little... compression check and listen for the hiss... in the intake and exhaust... don't be frightened if it does... because it just means that the valves are not seated... sticking valves are one thing that these engines do when they run hot and you run the multi vis oil...

they get carbon and gummy... a good way to clean it out is the old Reslone trick... as Skyking can tell you it helped clean his up right away... but, the folks at reslone don't make a aircraft product so your on your own... I know nothing about it... and I wouldn't run it all the time... probably the last 5-10 hrs before the oil change... you would be surprised at the differance after all the carbon comes out and the varnish is sent packing... again this is not a recomendation... as the lawyers will jump to me promoting something that the manufacture doesn't say anthing about... av blend is another one that is made for aircraft but, its more expensive... and I don't think it does as good a job... but, they do have approval from the faa... just not from the manufacture... who counts most...

As to his symptoms I would say that it is either a leaking intake... or sticking valve... and them leaks are hard to find... so it takes someone runing the engine while the other does the squirt test and checks...

compression test will tell me more .. as well as looking at the spark plugs... a cyc that is runing lean will have a bright and new looking plug.. while a normal one will be somewhat coffee colored... like the guy who came and gave the talk about spark plugs... you all missed... you would have been able to see one that was normal and one that is runing too lean... or burning... sorry... he is not doing that any more...he put on a very informative show... and gave away lots of info as well as some products... Champion was sold and now doesn't put out that any more... might be on the web though... might check... anyway awaiting for more test results.. and data... their Larry... don't make me come back their and hunt you down... smile... GMAs

WebMaster · #10 06-29-02, 11:05 PM

I have been running multi grade oil, because up until very recently, it has been cooler. SkyKing was right, this was my first flight in HOT weather. On my trip to beaver island, it was 74F, and we got the hot weather going into Meigs, and then the next day. I'll try some risolone, and get the oil changed. I'm calling the mechs on Monday, get it into the shop.
I'll have them check compression, and plugs.

WebMaster · #11 07-17-02, 12:41 PM

Well, GMAs was correct. Leaky fuel strainer O-Ring was causing air to get into the system. Also, mixture screw was off a bit, and the air cleaner was soggy, and it was hot.
Flys better than ever. New Plugs are on their way from Skyranch.biz (sacramento sky ranch), and they'll go in tomorrow night. Interestingly enough, even with shipping from the west coast, they are cheaper than anyone I could connect with.
Kevin should consider adding them to resources.
Thanks All.
OH, and we changed to straight Aeroshell 100W.

Bob Cook · #12 07-17-02, 02:35 PM

Larry

How many beavers are on Beaver island ? (wouldn't that that one)

been there by boat.

100W is the way to go in the summer.

check your baffles while changing plugs.

17th August Mackinaw ?

Bob

WebMaster · #13 07-18-02, 07:38 PM

It depends on how many twin tails show up

It is a neat place, though not as amenable as MCD for tourist.
August 17 at MCD is cool with us, we have a luncheon fly-in at 4N0, and then we'll be up. You are all welcome to have lunch with us.

Bob Cook · #14 07-18-02, 08:14 PM

Beaver island......not much. There was a corp aircraft that landed short of runway and people survived. First on the scene (pilot and copilot) didn't make it. Did you know about that one?

I would be coming up Friday night via the Great circle route out of NY which puts us over georgian bay and the middle of lake huron. Bit out of the way.

Now who else is going ? KEVEN ? maybe talk Don into coming.. is he back from Mexico yet ?

We should try and book some place to stay unless you want to camp under a wing (winging it).

bob