PLEASE HELP!! High CHT

H

Helicopter50

Filing Flight Plan
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Mar 21, 2012
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helicopter50
Good afternoon. I am asking this question because we are at wits end. I am a helicopter pilot for a police department in La. We currently operate a R44 with a Lycoming IO-540 engine. We are having a problem with HIGH cylinder head temps (red line). We have tried everything we can think of but can't find the solution. It over heats once you come into a hover for a few minutes.
We have:
1. checked the CHT probe. We have replaced it and its working fine.
2. The CHT gauge has also been checked and working properly
3.Checked plugs. They are proper plugs and in good condition
4. All 6 injectors removed and cleaned.
5. mags checked twice. Both times the timing was dead on.
6. fuel mixture cable working properly.
7. no intake leaks
8. cooling baffles ok
9. exhaust is good
:dunno:
my brain is fried. cant remember what else was done.:mad2:

I have noticed that the inside of our exhaust pipe is usually white white. Since this problem it has turned a brownish color.

Any sugestions will be greatly appreciated.

Brian
 
Helicopter50 said:
Good afternoon. I am asking this question because we are at wits end. I am a helicopter pilot for a police department in La. We currently operate a R44 with a Lycoming IO-540 engine. We are having a problem with HIGH cylinder head temps (red line). We have tried everything we can think of but can't find the solution. It over heats once you come into a hover for a few minutes.
We have:
1. checked the CHT probe. We have replaced it and its working fine.
2. The CHT gauge has also been checked and working properly
3.Checked plugs. They are proper plugs and in good condition
4. All 6 injectors removed and cleaned.
5. mags checked twice. Both times the timing was dead on.
6. fuel mixture cable working properly.
7. no intake leaks
8. cooling baffles ok
9. exhaust is good
:dunno:
my brain is fried. cant remember what else was done.:mad2:

I have noticed that the inside of our exhaust pipe is usually white white. Since this problem it has turned a brownish color.

Any sugestions will be greatly appreciated.

Brian
Click to expand...

Welcome to POA... great bunch of guys and gals here to visit with....
As for your High CHT issue.... Have you called Robinson ?:dunno:

Any motor in a heli lives a hellish life anyway and just one little thing out of place will cascade into a fiasco....

How are the EGT numbers?:dunno:
 
Thanks for the warm welcome. We talked to Lycoming and they could not offer any more advice than their trouble shooting page. We asked questions and they went down the check list. Not much help at all. Hopefully we will figure it out somehow. Change enough parts and almost 100 percent chance it will run right sooner or later.
 
The normal color of the tailpipe on a motor burning 100LL is a light brown color... If it is darker then normal then it's probably on the rich side. It is possible there is additional carbon build up on the tops of the piston and on the surface of the combustion chamber and the chance of a higher then normal compression ratio exists, that will create mild detonation and lead to elevated CHT's.... I am still curious as to the EGT numbers?
 
One cylinder, two or all of them?

I have a similar problem with an overhauled O-360 but only 1 cylinder. 5 (that's right 5!) A&Ps kept saying the baffles were fine, no problem. Took it to a 3rd shop, they discovered serious issues with the baffling. Inside where you need to be a contortionist, major air leakage. The oil cooler was improperly sealed, too. (Really annoying since this airplane's been thru 10 annuals and no one's caught it before)

Helicopter environment, 'specially LEO operations, is very different but don't just check the baffling, go over every inch of the baffling with a magnifying glass (well, not really, but pretend).

Which cylinders? Lycoming, ECI, Superior, etc? I've discovered the hard way that each has different recommendations for high CHTs.
 
Do you have a fuel flow gauge in gph, (not a pressure gauge; not pph)?
It would be nice to know what you are getting at full rich, full throttle.
Just wondering if the fuel is getting there.
The Cont 520 has a fuel screen, not sure about the Lyc - could be plugged with debris.
Could run booster pump with each injector in a cup, I believe there is a spec (if low, might indicate obstruction)
Might end up with a flow divider/fuel controller overhaul after its all done.
 
Check to see if the cold weather baffle kit is installed. It may have not been removed for the early warm weather.

José
 
Thanks everyone for responding. Not sure what the egts are running. #5 cylinder is the one running hot. Mechanics are bringing something to test the fuel flow tomorrow. The belts and fan were checked and had no slippage. No cold weather baffle kit either. Oh and forgot to say that this problem started right after getting an inspection. They replaced the mags. Went running perfect and came out hot as a firecracker. Im impressed withe you guys responses. I have been on forums in the past and folks try hard to be asses. Thanks everyone. Going to check your suggestions tomorrow.
 
Helicopter50 said:
We are having a problem with HIGH cylinder head temps (red line). We have tried everything we can think of but can't find the solution. It over heats once you come into a hover for a few minutes.
We have:
1. checked the CHT probe. We have replaced it and its working fine.
2. The CHT gauge has also been checked and working properly
Click to expand...

Is this a single probe, or do all the cylinders have them? Is the oil temperature gauge an electric type, and is it reading high, too?

A poor ground can do this. If there is ANY resistance in the ground cable between engine and airframe, or its attaching points, the alternator's charging current looks for other ways to get from the engine to the airframe and since the electron flow from the CHT probe (and oil temp probe) is in the same direction as the charging flow, the charging enters the CHT probe through its ground at the cylinder head and acts to boost the flow to the gauge and makes it overread. Cessna had this issue with its Rochester electric oil temp kits used to replace the old bulb-type mechanical gauges and had to start providing a ground wire to be installed between a case bolt near the probe and the gauge frame itself.

I would take a real close look at the grounding of the engine. Oil and corrosion, both around the cable bolts and inside the crimp terminals, can introduce resistance. It might not show on an ohmmeter when everything is cold, but the alternator current will soon heat it and increase its resistance and start making gauges look stupid.

Dan
 
Have you called the factory (Robinson) and spoke with a tech rep?

Typically the R44 runs normal range temps in the R44 even on hot days. How is the oil temp running? Is it hot also?
 
Helicopter50 said:
Good afternoon. I am asking this question because we are at wits end. I am a helicopter pilot for a police department in La. We currently operate a R44 with a Lycoming IO-540 engine. We are having a problem with HIGH cylinder head temps (red line). We have tried everything we can think of but can't find the solution. It over heats once you come into a hover for a few minutes.
We have:
1. checked the CHT probe. We have replaced it and its working fine.
2. The CHT gauge has also been checked and working properly
3.Checked plugs. They are proper plugs and in good condition
4. All 6 injectors removed and cleaned.
5. mags checked twice. Both times the timing was dead on.
6. fuel mixture cable working properly.
7. no intake leaks
8. cooling baffles ok
9. exhaust is good
:dunno:
my brain is fried. cant remember what else was done.:mad2:

I have noticed that the inside of our exhaust pipe is usually white white. Since this problem it has turned a brownish color.

Any sugestions will be greatly appreciated.

Brian
Click to expand...

Try operating LOP? Is this a recent problem? Was there a maintenance or other event that precipitated this?
 
Last edited:
Helicopter50 said:
Thanks everyone for responding. Not sure what the egts are running. #5 cylinder is the one running hot. Mechanics are bringing something to test the fuel flow tomorrow. The belts and fan were checked and had no slippage. No cold weather baffle kit either. Oh and forgot to say that this problem started right after getting an inspection. They replaced the mags. Went running perfect and came out hot as a firecracker. Im impressed withe you guys responses. I have been on forums in the past and folks try hard to be asses. Thanks everyone. Going to check your suggestions tomorrow.
Click to expand...


Dollars to donuts your timing is incorrect.
 
Dollars to donuts your timing is incorrect.
Click to expand...

The theory of unfixing the last thing worked on certainly applies here but he did state in post 1 that the timing had since been checked twice. Or maybe you mean internal timing?
 
Let'sgoflying! said:
The theory of unfixing the last thing worked on certainly applies here but he did state in post 1 that the timing had since been checked twice. Or maybe you mean internal timing?
Click to expand...

And the same mistake was made twice? Impulse malfunctioning so the timing is not being set to the timing that happens when the engine is running?
 
Let'sgoflying! said:
The theory of unfixing the last thing worked on certainly applies here but he did state in post 1 that the timing had since been checked twice. Or maybe you mean internal timing?
Click to expand...

All of it, points settings, the whole shmear, start from base and re-time everything so you know it's correct.
 
Helicopter50 said:
Thanks everyone for responding. Not sure what the egts are running. #5 cylinder is the one running hot. Mechanics are bringing something to test the fuel flow tomorrow. The belts and fan were checked and had no slippage. No cold weather baffle kit either. Oh and forgot to say that this problem started right after getting an inspection. They replaced the mags. Went running perfect and came out hot as a firecracker. Im impressed withe you guys responses. I have been on forums in the past and folks try hard to be asses. Thanks everyone. Going to check your suggestions tomorrow.
Click to expand...

On ECI's website (and talking with them) a possible issue is timing on the sparks. #5 is against the firewall, right? Is it also next to the oil cooler housing?

ECI has a list of 15 items to check for high CHTs on its website:

http://www.eci.aero/pages/tech.aspx#Troubleshoot

Something there might provide some additional ideas.
 
I don't want to hijack this thread, but what shop was able to find your problem? I have been having a high CHT problem on 3 our of 4 cylinders on my O-360 for a long time and 3 A&Ps have not found the problem. I am looking for a good fourth.

murphey said:
One cylinder, two or all of them?

I have a similar problem with an overhauled O-360 but only 1 cylinder. 5 (that's right 5!) A&Ps kept saying the baffles were fine, no problem. Took it to a 3rd shop, they discovered serious issues with the baffling. Inside where you need to be a contortionist, major air leakage. The oil cooler was improperly sealed, too. (Really annoying since this airplane's been thru 10 annuals and no one's caught it before)

Helicopter environment, 'specially LEO operations, is very different but don't just check the baffling, go over every inch of the baffling with a magnifying glass (well, not really, but pretend).

Which cylinders? Lycoming, ECI, Superior, etc? I've discovered the hard way that each has different recommendations for high CHTs.
Click to expand...
 
Paint can significantly affect the cylinder cooling. A heavy paint coat or multiple coats can increase the CHT by as much as 30 to 50 deg F. I experienced this myself on recoating cylinder fins that showed corrosion. A single light coat is all you need.

José
 
Piloto said:
Paint can significantly affect the cylinder cooling. A heavy paint coat or multiple coats can increase the CHT by as much as 30 to 50 deg F. I experienced this myself on recoating cylinder fins that showed corrosion. A single light coat is all you need.

José
Click to expand...

Very true, more than once I had to strip a "super nice" paint job off an engine fot this reason, just ran too hot. Paint serves as an insulator, light colors worse than dark. An air cooled engine should have a thin coat of flat black paint on any heat exchange surface.
 
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