High CHT on new overhaul

High CHT on new overhaul

At the time of overhaul for my O-540 J3C5D in a 1978 182RG I added a JPI 6 probe EGT/CHT monitor.  The engine has run hot since the overhaul and now after 20 hours of flight two cylinders are still showing excessively high CHTS. Cylinder #1 runs at 415-420 dF while #4 is consistently at 440+ dF.  These readings are at ambient temp of 35 dF, cowl flaps closed, almost full rich burning 18.5 gph.  Cylinder #5 which has the factory CHT probe attached to it is routinely 350 dF.
My A&P has replaced all of the baffling, checked for induction leaks, checked timing, checked carburetor for proper fuel flow, checked the probe leads, the probes themselves and the entire cowling.
Does anyone have experience with this engine, this problem and have a possible solution?  Thanks.

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Re: High CHT on new overhaul

Which cylinders does it have on it?

Walter

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Re: High CHT on new overhaul

It has overhauled Lycoming cylinders. 

Marty

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Re: High CHT on new overhaul

That fact that you have Lycoming cylinders probably takes that out of the equation.  The next step would be to go to the GAMI website and download the GAMI lean test and do the HIGH-LOW GAMI lean test.  This will tell me a LOT about the F:A balance and give me a very good idea about the induction system integrity.

If you want to do that test and fax me the charts, I'll be happy to take a look and see if I can help you figure this out.

Walter Atkinson
Advanced Pilot Seminars

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Re: High CHT on new overhaul

Martin, Why don't you put the factory probe into no.4 cylinder and compare the readings, just to make sure. Cheapest things first when faultfinding.

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Re: High CHT on new overhaul

OK, I see you are talking CHT...but in diagnosing a problem ust the full capabilities of the JPI.... What are your EGT reading for the cylinders?

If the fuel flow is lean on those cylinders then you know why the CHT is high.

Next, how is your baffling?  Since you put in a new engine I hope you put in new baffling as well.  And check on how well it seals against the upper cowl.  ALSO... Check to see if you have the aluminum baffles and springs on the bottom side of the cylinders.  If they are lose, missing or broken your temps will go up.

Barry
"Chop'd Liver"

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Re: High CHT on new overhaul

EGT's all  below 1160F running about 18.5 GPH.  Rich yes, but it's the only way to keep things even close to cool enough.  Baffling has just been replaced and we're checking to see how much difference that makes.
We have also checked the probes and found them to be indicating correctly. 
I have located two other early model 182RG owners who have had serious problems with the #4 cylinder which may point to a baffle design problem that never came to light prior to the multi-point engine monitoring systems now available.  If I had not installed my JPI EDM-700 at overhaul there is no way I would even be aware of what is going on with #1 and #4 running so hot.
Later 182RGs had the oil cooler moved to the rear and the turbos have at least one additional baffle near the #4 cylinder, which says to me that Cessna may have figured out they had a design flaw in the early versions of the model.  Mine is # 257.

Marty Coniglio

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Re: High CHT on new overhaul

Problem Solved!  After chasing everthing from induction leaks to valve clearances and replacing all of the baffle seals I suggested checking the mag timing.  Ah, it was advanced several degrees, causing the engine to run very hot.  With proper timing all of the CHTs are now below 400F and it seems that the sealing of all fixable leaks in the baffling have resulted in another knot or two of airspeed. 
Another testimonial for a multi-probe engine monitor, without it I would have burned up these new rings in no time and would be doing a top overhaul and scratching my head as to why.

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