#3 Cylinder Always Hottest

[Mike A]

Cylinder #3 on my TSIO-360-LB constantly runs 20-30 degrees hotter CHTs than any other cylinder. It limits my ability to run nice power settings by creeping up near 400 degrees while the rest are nicely 370 degrees or below. Any ideas on a culprit or do I just need to work on the baffling. It’s right below the oil filler door, and I suspect that may have something to do with it. 
 

Happy New Year!

[Yetti]

Yes.  For reasons of airflow dynamics it will be hottest.  That is why the original single probe from Mooney was on number 3.

[spistora]

11 hours ago, Mike A said:

Cylinder #3 on my TSIO-360-LB constantly runs 20-30 degrees hotter CHTs than any other cylinder. It limits my ability to run nice power settings by creeping up near 400 degrees while the rest are nicely 370 degrees or below. Any ideas on a culprit or do I just need to work on the baffling. It’s right below the oil filler door, and I suspect that may have something to do with it. 
 

Happy New Year!

I have the LB also and see exactly the same thing.

[stevesm20b]

I have the GB and # 3 is the hottest. The factory probe on mine is on the # 5 cyl.

[kortopates]

4 hours ago, Yetti said:

Yes.  For reasons of airflow dynamics it will be hottest.  That is why the original single probe from Mooney was on number 3.

Can't really compare a 4 cyl Lyc to a 6 cyl Cont - the cylinders aren't even numbered the same.

[kortopates]

37 minutes ago, stevesm20b said:

I have the GB and # 3 is the hottest. The factory probe on mine is on the # 5 cyl.

That's unusual that the factory probe is on a front cylinder, its usually in the #2, (rear pilot side).

[Yetti]

8 minutes ago, kortopates said:

Can't really compare a 4 cyl Lyc to a 6 cyl Cont - the cylinders aren't even numbered the same.

Ya I missed it.  I thought I saw a J in the plane description.   But you could argue that the probe is sitting between 2 other hot cylinders.

[anthonydesmet]

Continental TSIO-360MB and my #2 runs the hottest....about 20-25 degrees hotter.  Factory spark plug gasket probe is also on #5.

[milotron]

2 and 5 the hottest for me. #2 is next to the oil cooler so probably loses some flow there. #5 is doubled with the ship's probe so not really sure if it is high or low.

 

#2 is typically about 20-30 degrees warmer on mine too and is what I use to guide cowl flap opening.

 

 

Also, I think the oil filler door is over #4...Continentals have #1 at the copilot side rearmost cylinder.

[jlunseth]

#3 is not under the oil filler door, that door is actually aft of all the cylinders. See picture above.

I never remember which side are even and which are odd. I do know that 1 & 2 are the rearmost, and 5 & 6 are the front two. I am pretty sure that the odds are on the starboard side, that is, the right hand side if you are in the pilot’s seat. That would put #3 on the side of the engine opposite where the oil door is, although it is pretty much in the middle of the engine (going from one side to the other). One possible explanation is that the air intake is on that side, partially blocking the intake hole in the cowling, but then you would expect to see all the odd cylinders hotter than the evens and that is not the case in your engine, nor is it the case in mine. The one I have trouble with in my engine is #2. I think the problem is some small gaps in the baffling at the rear of the engine on that side. You can see a wrinkle in the baffling along the back on the port side. The baffling does not show signs that it is contacting the cowling at that point.

Have you run a Lean Test to see whether the mixture is close to those in the other cylinders? That is the first thing I would do, it is what Savvy says I should do. But I would guess that if its #3, either there is an issue with your probe, or that probe is still the factory probe while the others are from your engine monitor mfr., or there is an issue with your mixture on that cylinder. The front cylinders are generally cold because they are right in the inlet and the back because they are furthest from the inlet, but 3 & 4 have no excuses.

[kortopates]

16 minutes ago, jlunseth said:

I am pretty sure that the odds are on the starboard side, that is, the right hand side if you are in the pilot’s seat.

Yep, and that's true for both Lyc and TCM. Even side is on the pilot side.

That's a badly chaffed ignition wire as it passes by the oil cooler. I am sure its leaking - something you can see visually arcing in low light while running (but be careful if you try that). I'd have  it replaced soonest. They sell a kit to replace a single wire - always in grey though and will require the slick harness toolkit to replace it. I mention the kit since the wires don't look otherwise old or worn.

Edited January 2, 2021 by kortopates

[Guest]

From the K model maintenance manual, CHT probe location depends on serial number.

Clarence

[EricJ]

3 hours ago, jlunseth said:

I never remember which side are even and which are odd. I do know that 1 & 2 are the rearmost, and 5 & 6 are the front two. ...

The easy way to remember it is that Lycomings number from front to back, and Continentals number from back to front.   The cylinders are staggered, so on a Continental the rear-most cylinder is #1, the next moving forward, on the opposite side, is #2, etc., etc.

On a Lycoming the front-most cylinder is #1, then the next back on the opposite side is #2, etc.

 

[kortopates]

From the K model maintenance manual, CHT probe location depends on serial number.
Clarence

Good find Clarence, but what I've found from many Savvy subscribers that after engine overhaul the OEM CHT probe often doesn't get reinstalled in the same place and often goes into a more convenient rear cylinder.


Sent from my iPhone using Tapatalk

[Mike A]

Mine is a 1999 reman and the ship’s CHT is in 5, which is just about worthless. 

[jlunseth]

4 hours ago, kortopates said:

Yep, and that's true for both Lyc and TCM. Even side is on the pilot side.

That's a badly chaffed ignition wire as it passes by the oil cooler. I am sure its leaking - something you can see visually arcing in low light while running (but be careful if you try that). I'd have  it replaced soonest. They sell a kit to replace a single wire - always in grey though and will require the slick harness toolkit to replace it. I mention the kit since the wires don't look otherwise old or worn.

Good eye. The wires were all replaced just a few years ago. Plane goes in for the annual next week, so I will have it replaced. I don’t care what color they are, just that the plugs spark well.