Hi Guys!
I’m flying a Cessna 205 with a Continental IO-550 in it.

My CHT’s readings are similar except Cylinder 6

c1 390°F
c2 380°F
c3 365°F
c4 350°F
c5 370°F
c6 214°F

Is this something I should be worried about?
Is 200°F too cold for a Cylinder?

The airplane just came out of the last 200hours inspection.
Compressions and spark plugs are in good shape.

I live in Cancun, Mexico where temperatures are always above 80°F

Also JPI CHT probes are reasonably new

I would check the spark plugs on that cylinder.

Check plugs, and after you've run it again, swap the probe with the next cylinder. The thing that most people do wrong when troubleshooting is to try more than ONE thing at a time.
John

Definitely do the CHT probe wire cross check first.

Be advised I've seen two good jugs swapped out when a fancy engine gage had a few jugs mixed up, not me of course, I did have to change out two good mags when some googan miss wired the P leads before I got smart enough to always check on AC new to my shop.

Plugs will show on a mag check, unless they both FOD'ed out at the same time, unless you have a broken P-lead.

I did mostly float birds so a momentary low RPM mag kill check was part of the pre maintence run up to check for broken P lead and we could safely walk the wire.

Any chance your fuel flow shows a needle or two high, if so you have a plugged injector. Even if you don't the injector could be plugged. Were the injectors cleaned at the last 100H/Anual ?

Do a compression check, not a lot of the 206 birds I took care of had a 6 channel gage set but a few that ran that cool, even a little warmer, had a toasted exhaust valve or whatever and were not making power.


Rocket

rocket wrote:Definitely do the CHT probe wire cross check first.

Be advised I've seen two good jugs swapped out when a fancy engine gage had a few jugs mixed up, not me of course, I did have to change out two good mags when some googan miss wired the P leads before I got smart enough to always check on AC new to my shop.

Plugs will show on a mag check, unless they both FOD'ed out at the same time, unless you have a broken P-lead.

I did mostly float birds so a momentary low RPM mag kill check was part of the pre maintence run up to check for broken P lead and we could safely walk the wire.

Any chance your fuel flow shows a needle or two high, if so you have a plugged injector. Even if you don't the injector could be plugged. Were the injectors cleaned at the last 100H/Anual ?

Do a compression check, not a lot of the 206 birds I took care of had a 6 channel gage set but a few that ran that cool, even a little warmer, had a toasted exhaust valve or whatever and were not making power.


Rocket

Actually they just cleaned out the injectors, and that’s also when the problem showed up.

I will do the cross check of the probes

Also, how Cold is too Cold?


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The temp is not the issue, the issue is with that big a spread you have a cylinder issue power issue. If they touched the injectors that is where I would look first. Over the years I have found no better way to make a working unit stop working than to put a wrench on it. Another thought is do a in flight mag check at 2400 RPM. I have seen plugs do fine on run up drop out above 2100 RPM should show up with pressure test when cleaning but not everyone does that. DENNY

I've got the IO470 in my 205, and CHT spread is perhaps 50 degrees max under cruise or climb. I don't like to run over 400F, or under 300F. Too hot weakens the aluminum and decreases detonation margin. Too cool increases lead problems (sticky valves, fouling, etc). If I can get 350 in cruise across the board I'm happy.

Cylinder #1 is always the hottest (front left, gets the least cooling air being on the upstroke of the propeller). Excluding cylinder 6, I'd say your spread looks normal. If cylinder 6 was 314F, I'd say look at your baffling. At 214F, you have a problem. I'd look at a few things: 1) CHT probe. Either swap with another to confirm, or just replace it. 2) Injector clogged. Given that you just had them serviced, look there. 3) Manifold induction leak on one cylinder.

Do you monitor EGT's as well? If your cylinder #6 EGT is similar to the other cylinders (within 150F?), you probably have a CHT probe problem. If the EGT is way different, look at injector or leaking manifold.

I'll put my money on the CHT probe. If it's an injector or manifold leak, I'd think it wouldn't be running very well, and you'd notice.

jcadwell wrote:I've got the IO470 in my 205, and CHT spread is perhaps 50 degrees max under cruise or climb. I don't like to run over 400F, or under 300F. Too hot weakens the aluminum and decreases detonation margin. Too cool increases lead problems (sticky valves, fouling, etc). If I can get 350 in cruise across the board I'm happy.

Cylinder #1 is always the hottest (front left, gets the least cooling air being on the upstroke of the propeller). Excluding cylinder 6, I'd say your spread looks normal. If cylinder 6 was 314F, I'd say look at your baffling. At 214F, you have a problem. I'd look at a few things: 1) CHT probe. Either swap with another to confirm, or just replace it. 2) Injector clogged. Given that you just had them serviced, look there. 3) Manifold induction leak on one cylinder.

Do you monitor EGT's as well? If your cylinder #6 EGT is similar to the other cylinders (within 150F?), you probably have a CHT probe problem. If the EGT is way different, look at injector or leaking manifold.

I'll put my money on the CHT probe. If it's an injector or manifold leak, I'd think it wouldn't be running very well, and you'd notice.

On a IO-470 #1 cylinder is actually rear right. So if yours is the hottest you may have a baffling issue JC. I do agree that under 400 and over 300 is ideal. My 206 with a 520 usually runs about 360 max on cyls 3-6. 1 and 2 run cooler when I'm running LOP, about 280-290.
I find #6 can be tough to get hot enough as it is the front left and can often get too much airflow. Make sure they put all the baffling back on properly after annual. There should be a partial plate in front of #6 as it gets lots of air normally. #5 is behind the cooler and has a tendency to run hotter the #6 because of the cooler. First thing I'd do is swap the probe to a different location and see if the issue follows the probe.
I a

I probably mixed the number up. My front (pilot side) left is always a bit hotter than the others. I've screwed with it to no end, and talked with some other 205 owners that see the front left being hot. I've gotten them close enough now by fiddling with baffling that I'm content.

Pretty sure I've read somewhere in TCM guidance that it is good practice to consider 300 degrees a minimum.

pabloecanales wrote:[Actually they just cleaned out the injectors, and that’s also when the problem showed up.

This....... It really helps when we have ALL the information!!!! Yes, this is the FIRST thing to check out.
Why do I answer these things???!!!

As someone suggested, be sure first thing you do is crosscheck your CHT probe wires. Often maintenance will lead to displaced monitor probe wiring and loosened connections, which can lead to erroneous readings.

Good news guys!

I found a New CHT probe in my garage, which I proceeded to install immediately.

And the results are great, everything is back to normal

All Temps are now indicating around 380°F (which I know are hot, but at least they make sense)


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pabloecanales wrote:Good news guys!

I found a New CHT probe in my garage, which I proceeded to install immediately.

And the results are great, everything is back to normal

All Temps are now indicating around 380°F (which I know are hot, but at least they make sense)

380 isn't hot, especially in Cancun. Run it and have fun.